kth.sePublikationer
Ändra sökning
Avgränsa sökresultatet
123 1 - 50 av 145
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Träffar per sida
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
Markera
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 1.
    Ahmadzadeh, Karan
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Teoretisk kemi och biologi.
    Li, Xin
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Teoretisk kemi och biologi.
    Rinkevicius, Zilvinas
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Teoretisk kemi och biologi. Kaunas Univ Technol, Fac Math & Nat Sci, Dept Phys, LT-51368 Kaunas, Lithuania..
    Norman, Patrick
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Teoretisk kemi och biologi.
    Efficient Kohn-Sham density-functional theory implementation of isotropic spectroscopic observables associated with quadratic response functions2022Ingår i: Electronic Structure, E-ISSN 2516-1075, Vol. 4, nr 4, artikel-id 044004Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    For general exchange-correlation functionals with a dependence on the local spin densities and spin-density gradients, we provide computationally tractable expressions for the tensor-averaged quadratic response functions pertinent to the experimental observables in second-harmonic generation (SHG). We demonstrate how the tensor-averaged quantities can be implemented with reference to a derived minimal number of first- and second-order perturbed Fock matrices. Our consideration has the capability of treating a situation of resonance enhancement as it is based on damped response theory and allows for the evaluation of tensor-averaged resonant-convergent quadratic response functions using only similar to 25% (one-photon off-resonance regions) and similar to 50% (one-photon resonance regions) of the number of auxiliary Fock matrices required when explicitly calculating all the needed individual tensor components. Numerical examples of SHG intensities in the one-photon off-resonance region are provided for a sample of makaluvamine derivatives recognized for their large nonlinear optical responses as well as a benchmark set of small- and medium-sized organic molecules.

  • 2.
    Ahmadzadeh, Karan
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Teoretisk kemi och biologi.
    Li, Xin
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Teoretisk kemi och biologi.
    Rinkevicius, Zilvinas
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Teoretisk kemi och biologi.
    Norman, Patrick
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Teoretisk kemi och biologi.
    Zaleśny, Robert
    Wyb. Wyspiańskiego 27.
    Toward Accurate Two-Photon Absorption Spectrum Simulations: Exploring the Landscape beyond the Generalized Gradient Approximation2024Ingår i: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 15, nr 4, s. 969-974Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this Letter, we present a pioneering analysis of the density functional approximations (DFAs) beyond the generalized gradient approximation (GGA) for predicting two-photon absorption (2PA) strengths of a set of push-pull π-conjugated molecules. In more detail, we have employed a variety of meta-generalized gradient approximation (meta-GGA) functionals, including SCAN, MN15, and M06-2X, to assess their accuracy in describing the 2PA properties of a chosen set of 48 organic molecules. Analytic quadratic response theory is employed for these functionals, and their performance is compared against the previously studied DFAs and reference data obtained at the coupled-cluster CC2 level combined with the resolution-of-identity approximation (RI-CC2). A detailed analysis of the meta-GGA functional performance is provided, demonstrating that they improve upon their predecessors in capturing the key electronic features of the π-conjugated two-photon absorbers. In particular, the Minnesota functional MN15 shows very promising results as it delivers pleasingly accurate chemical rankings for two-photon transition strengths and excited-state dipole moments.

  • 3.
    Ahmadzadeh, Karan
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Scott, Mikael
    Ruprecht Karls Univ Heidelberg, Interdisciplinary Ctr Sci Comp, Neuenheimer Feld 205, D-69120 Heidelberg, Germany..
    Brand, Manuel
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Vahtras, Olav
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Li, Xin
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Rinkevicius, Zilvinas
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi. Kaunas Univ Technol, Fac Math & Nat Sci, Dept Phys, LT-51368 Kaunas, Lithuania..
    Norman, Patrick
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Efficient implementation of isotropic cubic response functions for two-photon absorption cross sections within the self-consistent field approximation2021Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 154, nr 2, artikel-id 024111Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Within the self-consistent field approximation, computationally tractable expressions for the isotropic second-order hyperpolarizability have been derived and implemented for the calculation of two-photon absorption cross sections. The novel tensor average formulation presented in this work allows for the evaluation of isotropic damped cubic response functions using only similar to 3.3% (one-photon off-resonance regions) and similar to 10% (one-photon resonance regions) of the number of auxiliary Fock matrices required when explicitly calculating all the needed individual tensor components. Numerical examples of the two-photon absorption cross section in the one-photon off-resonance and resonance regions are provided for alanine-tryptophan and 2,5-dibromo-1,4-bis(2-(4-diphenylaminophenyl)vinyl)-benzene. Furthermore, a benchmark set of 22 additional small- and medium-sized organic molecules is considered. In all these calculations, a quantitative assessment is made of the reduced and approximate forms of the cubic response function in the one-photon off-resonance regions and results demonstrate a relative error of less than similar to 5% when using the reduced expression as compared to the full form of the isotropic cubic response function.

  • 4. Ai, Yuejie
    et al.
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Ji, Yongfei
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Song, Wei-Guo
    Luo, Yi
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Hydrophobicity and Hydrophilicity Balance Determines Shape Selectivity of Suzuki Coupling Reactions Inside Pd@meso-SiO2 Nanoreactor2016Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, nr 19, s. 10244-10251Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Molecular sorting and catalysis directed by shape selectivity have been extensively applied in porous extended frameworks for a low-carbon, predictable, renewable component of modern industry. A comprehensive understanding of the underlying recognition mechanism toward different shapes is unfortunately still missing, owing to the lack of structural and dynamic information under operating conditions. We demonstrate here that such difficulties can be overcome by state-of-the-art molecular dynamics simulations which provide atomistic details that are not accessible experimentally, as exemplified by our interpretation for the experimentally observed aggregation induced shape selectivity for Suzuki C-C coupling reaction catalyzed by Pd particles in mesoporous silica. It is found that both aggregation ability and aggregating pattern of the reactants play the decisive role in controlling the shape selectivity, which are in turn determined by the balance between the hydrophobicity and hydrophilicity of the reactants, or in other words, by the balance between the noncovalent hydrogen bonding interaction and van der Waals forces. A general rule that allows prediction of the shape selectivity of a reactant has been proposed and verified against experiments. We show that molecular modeling is a powerful tool for rational design of new mesoporous systems and for the control of catalytic reactions that are important for the petrochemical industry.

  • 5. Bai, Linyi
    et al.
    Zhu, Liangliang
    Ang, Chung Yen
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Wu, Shaojue
    Zeng, Yongfei
    Ågren, Hans
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Zhao, Yanli
    Iron( III)-Quantity-Dependent Aggregation-Dispersion Conversion of Functionalized Gold Nanoparticles2014Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 20, nr 14, s. 4032-4037Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Developing gold nanoparticles (AuNPs) with well-designed functionality is highly desirable for boosting the performance and versatility of inorganic-organic hybrid materials. In an attempt to achieve ion recognition with specific signal expressions, we present here 4-piperazinyl-1,8-naphthalimide-functionalized AuNPs for the realization of quantitative recognition of Fe-III ions with dual (colorimetric and fluorescent) output. The research takes advantage of 1)quantity-controlled chelation-mode transformation of the piperazinyl moiety on the AuNPs towards Fe-III, thereby resulting in an aggregation-dispersion conversion of the AuNPs in solution, and 2)photoinduced electron transfer of a naphthaimide fluorophore on the AuNPs, thus leading to reversible absorption and emission changes. The functional AuNPs are also responsive to pH variations. This strategy for realizing the aggregation-dispersion conversion of AuNPs with returnable signal output might exhibit application potential for advanced nanoscale chemosensors.

  • 6.
    Brand, Manuel
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi. KTH Royal Inst Technol, Dept Theoret Chem & Biol, Sch Engn Sci Chem Biotechnol & Hlth, SE-10691 Stockholm, Sweden..
    Ahmadzadeh, Karan
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi. KTH Royal Inst Technol, Dept Theoret Chem & Biol, Sch Engn Sci Chem Biotechnol & Hlth, SE-10691 Stockholm, Sweden..
    Li, Xin
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, Parallelldatorcentrum, PDC. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi. KTH Royal Inst Technol, Dept Theoret Chem & Biol, Sch Engn Sci Chem Biotechnol & Hlth, SE-10691 Stockholm, Sweden..
    Rinkevicius, Zilvinas
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi. Department of Physics, Faculty of Mathematics and Natural Sciences, Kaunas University of Technology, LT-51368 Kaunas, Lithuania.
    Saidi, Wissam A.
    Univ Pittsburgh, Dept Mech Engn & Mat Sci, Pittsburgh, PA 15261 USA..
    Norman, Patrick
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi. KTH Royal Inst Technol, Dept Theoret Chem & Biol, Sch Engn Sci Chem Biotechnol & Hlth, SE-10691 Stockholm, Sweden..
    Size-dependent polarizabilities and van der Waals dispersion coefficients of fullerenes from large-scale complex polarization propagator calculations2021Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 154, nr 7, artikel-id 074304Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    While the anomalous non-additive size-dependencies of static dipole polarizabilities and van der Waals C-6 dispersion coefficients of carbon fullerenes are well established, the widespread reported scalings for the latter (ranging from N-2.2 to N-2.8) call for a comprehensive first-principles investigation. With a highly efficient implementation of the linear complex polarization propagator, we have performed Hartree-Fock and Kohn-Sham density functional theory calculations of the frequency-dependent polarizabilities for fullerenes consisting of up to 540 carbon atoms. Our results for the static polarizabilities and C-6 coefficients show scalings of N-1.2 and N-2.2, respectively, thereby deviating significantly from the previously reported values obtained with the use of semi-classical/empirical methods. Arguably, our reported values are the most accurate to date as they represent the first ab initio or first-principles treatment of fullerenes up to a convincing system size.

  • 7.
    Brand, Manuel
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Teoretisk kemi och biologi.
    Dreuw, Andreas
    Ruprecht Karls Univ Heidelberg, Interdisciplinary Ctr Sci Comp, D-69120 Heidelberg, Germany..
    Norman, Patrick
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Teoretisk kemi och biologi.
    Li, Xin
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, Parallelldatorcentrum, PDC.
    Efficient and Parallel Implementation of Real and Complex Response Functions Employing the Second-Order Algebraic-Diagrammatic Construction Scheme for the Polarization Propagator2023Ingår i: Journal of Chemical Theory and Computation, ISSN 1549-9618, E-ISSN 1549-9626, Vol. 20, nr 1, s. 103-113Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present the implementation of an efficient matrix-folded formalism for the evaluation of complex response functions and the calculation of transition properties at the level of the second-order algebraic-diagrammatic construction (ADC(2)) scheme. The underlying algorithms, in combination with the adopted hybrid MPI/OpenMP parallelization strategy, enabled calculations of the UV/vis spectra of a guanine oligomer series ranging up to 1032 contracted basis functions, thereby utilizing vast computational resources from up to 32,768 CPU cores. Further analysis of the convergence behavior of the involved iterative subspace algorithms revealed the superiority of a frequency-separated treatment of response equations even for a large spectral window, including 101 frequencies. We demonstrate the applicability to general quantum mechanical operators by the first reported electronic circular dichroism spectrum calculated with a complex polarization propagator approach at the ADC(2) level of theory.

  • 8.
    Brand, Manuel
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Teoretisk kemi och biologi.
    Dreuw, Andreas
    Norman, Patrick
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Teoretisk kemi och biologi.
    Li, Xin
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Teoretisk kemi och biologi.
    Efficient parallel implementation of complex response functions employing the algebraic-diagrammatic construction schemeManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    We present the derivation and implementation of an efficient matrix-folded formalism for the evaluation of complex response functions at the level of the second-order algebraic-diagrammatic construction ADC(2) scheme. The adopted hybrid MPI/OpenMP parallelization strategy enables the utilization of vast computational resources without significant performance losses as demonstrated by consistent size-scalings for the computationally most demanding steps obtained from calculations of the UV/vis spectra of a guanine oligomer series ranging up to 1,032 contracted basis functions. Further analysis of the convergence behavior of the involved iterative subspace algorithm revealed the superiority of a frequency-separated treatment of response equations even for a large spectral window including 101 frequencies. We demonstrate the applicability to general quantum mechanical operators by the first reported electric circular dichroism spectrum calculated with the complex polarization propagator approach at the ADC(2) level of theory.

  • 9. Bu, L.
    et al.
    Chen, J.
    Wei, X.
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Ågren, Hans
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Xie, Y.
    An AIE and ICT based NIR florescent probe for cysteine and homocysteine2017Ingår i: Dyes and pigments, ISSN 0143-7208, E-ISSN 1873-3743, Vol. 136, s. 724-731Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A combination of aggregation-induced emission and intramolecular charge transfer was achieved by using a triphenylamine analogue and a dicyanovinyl moiety as the electron donating and accepting units, respectively. Hence, we designed and synthesized a probe with a D-π-A framework as a near-infrared fluorescence turn-on probe for biothiols (cysteine and homocysteine). Owing to the remarkable intramolecular charge transfer effect as well as intramolecular rotations associated with the donor moiety, the probe exhibits extremely weak fluorescence, which becomes a good starting point for developing fluorescence “turn-on” probes. Upon reaction with cysteine or homocysteine utilizing the dicyanovinyl moiety, the intramolecular charge transfer character was weakened, and the reacting products were observed to aggregate in aqueous solutions, resulting in the aggregation-induced emission effect with red fluorescence at 651 and 656 nm, respectively. Hence, the probe could be used as a fluorescence “turn-on” sensor for cysteine and homocysteine, with the sensing time of less than 4 min and the detection limits of 8.4 μM and 5.7 μM towards cysteine and homocysteine, respectively. The probe could distinguish cysteine and homocysteine from glutathione. The sensing mechanism was systematically investigated by employing high resolution mass spectrometry, 1H NMR and density functional theory calculations as well as checking the solvent viscosity dependent fluorescence, and thus the nucleophilic addition products, the intramolecular charge transfer character, and the aggregation-induced emission behaviour were clearly elucidated. It is noteworthy that the low cytotoxicity, the intrinsic aggregation-induced emission nature and near-infrared emissions enable the application of the probe in living cell imaging.

  • 10. Cai, Shengyun
    et al.
    Hu, Xiaohao
    Tian, Guojian
    Zhou, Haitao
    Chen, Wei
    Huang, Jinhai
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Su, Jianhua
    Photo-stable substituted dihydroindolo[2,3-b]carbazole-based organic dyes: tuning the photovoltaic properties by optimizing the pi structure for panchromatic DSSCs2014Ingår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 70, nr 43, s. 8122-8128Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Three dihydroindolo[2,3-b]carbazole (DDC) donor based organic dyes (DDC6-DDC8) with long conjugated systems were successfully synthesized and characterized by optical, electrochemical, computational analysis, and photovoltaic methods. It was found that the elongated pi system as well as the high molar extinction coefficients (4.2-5.3 M-1 cm(-1)) sufficiently reinforced the light harvesting ability with the IPCE response of one dye DDC8 extended to 850 nm, which resulted in large J(sc) of these dyes based devices (high as 16.41 mA cm(-2)). The attached alkyl chains suppress the dark current to some extent, resulting the DDC6 and DDC7 devices in high V-oc, while DDC8 displayed low V-oc, because BTD in DDC8 could attract the iodine ion, which could accelerate the charge recombination. Among the three dyes, DDC7 displayed the best performance with an eta value 6.53% under 4 mu m thick scattering layer (condition 1+1), which was boosted to 7.49% under 8 mu m thick scattering layer (condition 1+2). The photo-stability measurements indicated that all the three dyes are fairly photo-stable.

  • 11. Chen, Bin
    et al.
    Ding, Yubin
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Zhu, Weihong
    Hill, Jonathan P.
    Ariga, Katsuhiko
    Xie, Yongshu
    Steric hindrance-enforced distortion as a general strategy for the design of fluorescence "turn-on" cyanide probes2013Ingår i: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 49, nr 86, s. 10136-10138Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    For the rational design of fluorescence "turn-on" cyanide probes, a general strategy is developed by introducing a dicyanovinyl group at the sterically demanding position of a large pi framework.

  • 12. Chen, Bin
    et al.
    Sun, Xi
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Ågren, Hans
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Xie, Yongshu
    TICT based fluorescence "turn-on" hydrazine probes2014Ingår i: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 199, s. 93-100Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Fluorescence "turn-on" probes PC3 and C3 with weak background emissions were developed for hydrazine sensing. The aldehyde and dicyanovinyl groups were used as the recognition units for PD and C3, respectively. Because of low reactivity of the aldehyde group, the fluorescence of PC3 was enhanced by only ca. 93 folds upon addition of a large amount of 1646 eq. hydrazine. In contrast, 0 exhibited fluorescence enhancement by ca. 239 folds upon addition of only 1.3 eq. hydrazine, and thus it showed high sensitivity towards hydrazine, with the detection limit of 7 ppb. In aqueous systems, it also works well with improved selectivity for hydrazine over CN-. The weak fluorescence of PC3 and 0 can be ascribed to twisted intramolecular charge transfer (TICT) processes by the combination of the bulky diphenylamino and 9-anthryl units, which were well demonstrated by theoretical calculations, viscosity dependent fluorescence, and fluorescence decay behaviour. Addition of hydrazine induced the disappearance of the TICT deactivation pathway, resulting in the observed fluorescence enhancement. It can be concluded that the combination of the bulky diphenylamino and 9-anthryl units is an effective approach for developing fluorescence turn-on hydrazine probes based on the TICT mechanism.

  • 13. Chen, Bin
    et al.
    Yu, Gang
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Ding, Yubin
    Wang, Cheng
    Liu, Zhiwei
    Xie, Yongshu
    Full-colour luminescent compounds based on anthracene and 2,2 '-dipyridylamine2013Ingår i: Journal of Materials Chemistry C, ISSN 2050-7526, Vol. 1, nr 44, s. 7409-7417Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Starting from two simple units of anthracene and 2,2'-dipyridylamine, a series of new luminescent compounds 1-8 were designed and synthesized by a combined strategy of changing the connection mode between the two units, extending the conjugation size, and introducing an additional electron donor. Photophysical properties of 1-8 were investigated and discussed on the basis of solvatochromic behaviour, theoretical calculations, crystal structure, and optimized structures. Interestingly, the emission wavelengths of these compounds could be successfully tuned from violet to red both in solutions and the solid-state, and prominent positive solvatochromism was observed for the compounds with a D-p-A framework. Consider compound 7 as an example, it shows peaks at 526 nm and 627 nm in cyclohexane and DMSO, respectively. Meanwhile, the quantum yield was decreased from 0.80 in cyclohexane to 0.12 in DMSO. The introduction of bulky groups was demonstrated to be effective for suppressing the aggregation effect and thus improving the solid state emission quantum yield. These results indicate that the combined structure modulation strategy offers a powerful tool for tuning the emission behaviour. To demonstrate the possibility of practical applications, 2 was employed as the emitting material for the fabrication of deep-blue organic light-emitting diodes (OLEDs), which showed a maximum external quantum efficiency of 2.2%. The CIE coordinates of (0.15, 0.08) are indicative of excellent blue color purity.

  • 14. Chen, Long
    et al.
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Ying, Weijiang
    Zhang, Xiaoyu
    Guo, Fuling
    Li, Jing
    Hua, Jianli
    5,6-Bis(octyloxy)benzo[c][1,2,5]thiadiazole-Bridged Dyes for Dye-Sensitized Solar Cells with High Open-Circuit Voltage Performance2013Ingår i: European Journal of Organic Chemistry, ISSN 1434-193X, E-ISSN 1099-0690, nr 9, s. 1770-1780Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Three new metal-free dyes with a 5,6-bis(octyloxy) benzo[c][1,2,5] thiadiazole core (DOBT-I-III) have been designed and synthesized for use as DSSCs. Their absorption properties and electrochemical and photovoltaic performances have been investigated systematically. The DSSCs based on DOBT-I-III show high open-circuit voltages (V-oc) of 829, 818, and 784 mV, respectively. Of the three dyes, DOBT-III, which contains a thiophene-bridging linker, exhibits the best photovoltaic performance: a short-circuit photocurrent density (J(sc)) of 12.74 mA cm(-2) and a fill factor (FF) of 0.73, which corresponds to an overall conversion efficiency of 7.29% under standard global AM 1.5 solar conditions.

  • 15. Chen, S.
    et al.
    Li, W.
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Zhu, W. -H
    Aggregation-controlled photochromism based on a dithienylethene derivative with aggregation-induced emission2017Ingår i: Journal of Materials Chemistry C, ISSN 2050-7526, E-ISSN 2050-7534, Vol. 5, nr 10, s. 2717-2722Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report novel aggregation-induced emission (AIE) characteristics involving aggregation-controlled photochromism properties of a dithienylethene derivative, BTE-EQ, where two quinolinemalononitrile (EQ) units are covalently attached to a dithienylethene core. The typical AIE effect of BTE-EQ has been found to originate from the AIE character of the EQ units with respect to the reference compound BTE, which does not contain an EQ unit. The photochromism study, together with density functional theory calculations, reveals that the photochromic activity of BTE-EQ can be reversibly switched off and on by controlling the aggregation state during the AIE process, which provides a novel route to controlling the photochromism of diarylethenes.

  • 16. Chen, S.
    et al.
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Song, L.
    A fluorescent photochromic diarylethene based on naphthalic anhydride with strong solvatochromism2017Ingår i: RSC Advances, E-ISSN 2046-2069, Vol. 7, nr 47, s. 29854-29859Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A novel "push-pull" diarylethene molecule consisting of an electron withdrawing ethene bridge (1,8-naphthalic anhydride) and two moderate electron donating side chains (2,5-dimethylthiophene) has been designed and synthesized. The photochromism study, together with density functional theory calculations, revealed that the molecule exhibits reversible fluorescence switching capacity upon photo-isomerization and remarkable solvatochromism with red shift of the fluorescence maximum by more than 150 nm owing to intramolecular charge transfer.

  • 17. Chen, Shangjun
    et al.
    Li, Wenlong
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Zhu, Wei-Hong
    Substitution effect on the photochromic properties of benzo[b]thiophene-1,1-dioxide based diarylethenes2015Ingår i: RSC Advances, E-ISSN 2046-2069, Vol. 5, nr 106, s. 87626-87634Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Benzo[b]thiophene-1,1-dioxide based diarylethenes (DAEs), BTT-1 to BTT-4, containing methyl, phenyl, formyl and triphenylamine groups at the 5,5'-position of the thiophene rings have been developed for gaining an insight into the substituent effect on the absorption and photochromic properties. Electron-donating substituents, such as phenyl and triphenylamine groups, are found to be effective at shifting the absorption band to a longer wavelength and decreasing the cyclization quantum yield. The electron-withdrawing formyl group can increase the cyclization quantum yield, but it reduces the thermal stability of the ring-closed isomer to some extent. BTT-4 bearing a triphenylamine group shows the poorest fatigue resistance among these four compounds, which is possibly due to the larger extended pi-conjugation length in the ring-closed isomer. BTT-2 bearing a phenyl unit undergoes typical photochromic reaction not only in solution, but also in PMMA thin film and in bulky crystals with excellent fatigue resistance and thermal stability.

  • 18. Chen, Wei
    et al.
    Zhang, Zhiyun
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Ågren, Hans
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Su, Jianhua
    Highly sensitive detection of low-level water content in organic solvents and cyanide in aqueous media using novel solvatochromic AIEE fluorophores2015Ingår i: RSC Advances, E-ISSN 2046-2069, Vol. 5, nr 16, s. 12191-12201Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A great deal of effort has been devoted to develop easy-to-use fluorescent probes for detecting analytes due to their advantages in the field of chemo- and bio-sensing. Herein, two novel 2,2 '-biindenyl-based derivatives BDM and BDBM containing dicyanovinyl groups have been designed and synthesized, and are shown to possess the remarkable dual properties of solvatochromism and aggregation-induced emission enhancement (AIEE). Importantly, both of them are found to serve as fluorescent indicators for the qualitative and quantitative detection of low-level water in organic solvents. Meanwhile, both BDM and BDBM emit yellowish orange and orange fluorescence, respectively, in their aggregated states. Furthermore, with dicyanovinyl groups as the recognition sites, both compounds can act as colourimetric and fluorescent sensors for highly sensitive and selective detection of cyanide in aqueous media, and the apparent response signals can be observed by the naked eye even in the presence of various interference anions, promising practical applications for detecting cyanide in drinking water. Besides, optical spectroscopic techniques, NMR titration measurements, and density functional theory calculations are conducted to rationalize the sensing mechanisms of the two probes.

  • 19. Chen, X.
    et al.
    Zhu, L.
    Wang, D.
    Zou, Q.
    Li, Xin
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Chen, W.
    A unimolecular platform based on diarylethene with multiple stimuli-gated photochromism2019Ingår i: Dyes and pigments, ISSN 0143-7208, E-ISSN 1873-3743, Vol. 164, s. 91-96Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The gated photochromic systems have attracted great interest in scientific researches due to their merits in the opto-electronic fields, whereas the multi-stimuli gating function in a unimolecular platform has rarely been addressed. Herein, a new strategy to realize multi-stimuli gated photochromic function was devised relying on a simple Schiff-based diarylethene derivative. The compound shows no photoswitching properties in solution under irradiation with any wavelength of light. It is noteworthy that mecury(II) ions, water and protons can trigger its photo-reactivity independently with different absorption changes, respectively. Therefore, a molecular logic circuit with four inputs, including mecury(II) ions, water, protons and UV light, was fabricated on the basis of the unimolecular platform, suggesting promise for application in multi-controlled photoswitchings. These results could be valuable for the further development of photoswitchings with multiple stimuli responses.

  • 20. Ding, Li
    et al.
    Zhang, Zhiyun
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Su, Jianhua
    Highly sensitive determination of low-level water content in organic solvents using novel solvatochromic dyes based on thioxanthone2013Ingår i: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 49, nr 66, s. 7319-7321Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Two thioxanthone-based fluorescent probes exhibited prominent solvatofluorochromism, and they were further found to be useful as fluorescence indicators for the qualitative and quantitative detection of low-level water content in various solvent media.

  • 21. Ding, Yubin
    et al.
    Li, Tong
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Zhu, Weihong
    Xie, Yongshu
    From nonconjugation to conjugation: novel meso-OH substituted dipyrromethanes as fluorescence turn-on Zn2+ probes2013Ingår i: Organic and biomolecular chemistry, ISSN 1477-0520, E-ISSN 1477-0539, Vol. 11, nr 16, s. 2685-2692Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Most reported Zn2+ probes suffer from the interference of background fluorescence originated from the conjugated structures of commonly utilized fluorophores. In this work, three novel meso-hydroxyl group substituted dipyrromethanes DPMOH1-DPMOH3 were synthesized and found to be colourless and nonfluorescent due to the interruption of the conjugated p system by an sp(3) carbon between the two pyrrolic units. Interestingly, only the addition of Zn2+ to the solutions of DPMOH1-DPMOH3 promoted their oxidation to dipyrrin forms, and bright fluorescence "turn on" was observed due to the formation of corresponding dipyrrin complexes with the dipyrrin : zinc stoichiometry of 2 :1. Zn2+ detection mechanism was investigated by UV-Vis, fluorescence, H-1 NMR and HRMS analyses, which can be ascribed to the CHEF type fluorescence enhancement, resulting from good rigidity of the dipyrrin complexes. Hence, DPMOH1-DPMOH3 can be used as fluorescence turn-on Zn2+ probes with the advantage of no background fluorescence.

  • 22. Ding, Yubin
    et al.
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Hill, Jonathan P.
    Ariga, Katsuhiko
    Ågren, Hans
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Andreasson, Joakim
    Zhu, Weihong
    Tian, He
    Xie, Yongshu
    Acid/Base Switching of the Tautomerism and Conformation of a Dioxoporphyrin for Integrated Binary Subtraction2014Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 20, nr 40, s. 12910-12916Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Compared with most of the reported logic devices based on the supramolecular approach, systems based on individual molecules can avoid challenging construction requirements. Herein, a novel dioxoporphyrin DPH22 was synthesized and two of its tautomers were characterized by single-crystal X-ray diffraction studies. Compound DPH22 exhibits multichannel controllable stepwise tautomerization, protonation, and deprotonation processes through interactions with H and F- ions. By using the addition of H+ and F- ions as inputs and UVNis absorption values at.1=412, 510, 562, and 603 nm as outputs, the controlled tautomerism of DPH22 has been successfully used for the construction of an integrated molecular level half-subtractor and comparator. In addition, this acid/base-switched tautomerism is reversible, thus endowing the system with ease of reset and recycling; consequently, there is no need to modulate complicated intermolecular interactions and electron-/chargetransfer processes.

  • 23. Ding, Yubin
    et al.
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Li, Tong
    Zhu, Weihong
    Xie, Yongshu
    alpha-Monoacylated and alpha,alpha '- and alpha,beta '-Diacylated Dipyrrins as Highly Sensitive Fluorescence "Turn-on" Zn2+ Probes2013Ingår i: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 78, nr 11, s. 5328-5338Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    With the purpose of developing readily synthesized CHEF (chelation-enhanced fluorescence) type Zn2+ probes with relatively simple molecular structures and excellent sensing behavior, p-anisoyl chloride was used for the acylation of 5-(pentafluorophenyl)dipyrromethane. Interestingly, the alpha,beta'-diacylated product PS2 with a unique substitution mode was obtained in high yield in addition to the normal a-substituted mono- and diacylated products PSI and PS3. Further oxidation of PS1-PS3 afforded dipyrrins S1-S3. Crystal structure and H-1 NMR measurements of S2 demonstrate the existence of a pure tautomer, which is consistent with DFT calculations. S1-S3 show highly Zn2+ selective "turn-on" fluorescence based on a CHEF mechanism by the formation of 2:1 (probe:metal) Zn2+ complexes. The emission colors can be easily tuned from green to red by changing the dipyrrin substitution modes. Furthermore, these probes demonstrate fast responses and wide applicable pH ranges. Among them, S2 shows the highest Zn2+ sensitivity, with a detection limit of 4.4 x 10(-8) M.

  • 24.
    Fransson, Thomas
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Delcey, Mickael G.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Brumboiu, Iulia E.
    Nicolaus Copernicus University, Torun.
    Hodecker, Manuel
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Li, Xin
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Rinkevicius, Zilvinas
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Dreuw, Andreas
    Heidelberg University.
    Rhee, Young Min
    orea Advanced Institute of Science and Technology (KAIST).
    Norman, Patrick
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Computational Chemistry from Laptop to HPC: A notebook exploration of quantum chemistry2022 (uppl. 1)Bok (Övrigt vetenskapligt)
    Abstract [en]

    Quantum chemistry is a powerful tool. It is now possible to model complex chemical processes even on a laptop getting insights into matter at its fundamental scale.

    But quantum chemistry is also very complex. Answering a chemical question requires selecting parameters among a wide variety of choices. Choosing a model system, an electronic structure method, a basis set, a set of properties, and a wide array of parameters which can affect the results in small but sometimes meaningful way… It can be a very daunting task, even for veterans of the field.

    Similarly, for those who wish to get a deeper understanding of a method, going through the pages of equation often riddled with inconsistent notations and formulations is very challenging. And at the end, the link between the equation and the computer implementation found in existing softwares can be vague at best.

    We believe that a core issue is that humans are not good at learning in abstract terms. We can get very far with a lecture or a textbook, but we will never build as much intuition about how a clock work as by simply breaking one apart and rebuilding it from scratch.

    This is exactly the aim of this page, allowing a hands-on approach to computational chemistry. Together we will dismantle the black box that a computational chemistry code often seems to be, go through all the cogs and gears, and build back together some of the main computational methods of modern computational chemistry. We will do this by presenting the underlying equations, all expressed with consistent notations, as well as by suggesting a simple python implementation, to really display in action how the theory is implemented into a practical tool. Additionally, we will put these methods in context by showing how they can be used to address concrete chemical questions, discussing the strengths and weaknesses of each method and how to best use them to solve practical problems.

  • 25.
    Fransson, Thomas
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Teoretisk kemi och biologi.
    Delcey, Mickael G
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Teoretisk kemi och biologi.
    Brumboiu, Iulia Emilia
    Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, 87-100 Toruń, Poland.
    Hodecker, Manuel
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Teoretisk kemi och biologi.
    Li, Xin
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Teoretisk kemi och biologi.
    Rinkevicius, Zilvinas
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Teoretisk kemi och biologi.
    Dreuw, Andreas
    Interdisciplinary Center for Scientific Computing, Heidelberg University, Im Neuenheimer Feld 205, 69120 Heidelberg, Germany, Im Neuenheimer Feld 205.
    Rhee, Young Min
    Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea.
    Norman, Patrick
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Teoretisk kemi och biologi.
    eChem: A Notebook Exploration of Quantum Chemistry2023Ingår i: Journal of Chemical Education, ISSN 0021-9584, E-ISSN 1938-1328, Vol. 100, nr 4, s. 1664-1671Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The eChem project features an e-book published as a web page (10.30746/978-91-988114-0-7), collecting a repository of Jupyter notebooks developed for the dual purpose of explaining and exploring the theory underlying computational chemistry in a highly interactive manner as well as providing a tutorial-based presentation of the complex workflows needed to simulate embedded molecular systems of real biochemical and/or technical interest. For students ranging from beginners to advanced users, the eChem book is well suited for self-directed learning, but workshops led by experienced instructors and targeting student bodies with specific needs and interests can readily be formed from its components. This has been done by using eChem as the base for a workshop directed toward graduate students learning the theory and practices of quantum chemistry, resulting in very positive assessment of the interactive nature of this framework. The members of the eChem team are engaged in both education and research, and as a mirroring activity, we develop the open-source software upon which this e-book is predominantly based. The overarching vision and goal of our work is to provide a science- and education-enabling software platform for quantum molecular modeling on contemporary and future high-performance computing systems, and to document the resulting development and workflows in the eChem book.

  • 26. Hede, T.
    et al.
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Leck, C.
    Tu, Yaoquan
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Ågren, Hans
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Model HULIS compounds in nanoaerosol clusters: investigations of surface tension and aggregate formation using molecular dynamics simulations2011Ingår i: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 11, nr 13, s. 6549-6557Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cloud condensation nuclei act as cores for water vapour condensation, and their composition and chemical properties may enhance or depress the ability for droplet growth. In this study we use molecular dynamics simulations to show that model humic-like substances (HULIS) in systems containing 10 000 water molecules mimic experimental data well referring to reduction of surface tension. The model HULIS compounds investigated in this study are cis-pinonic acid (CPA), pinic acid (PAD) and pinonaldehyde (PAL). The structural properties examined show the ability for the model HULIS compounds to aggregate inside the nanoaerosol clusters.

  • 27. Hede, Thomas
    et al.
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Leck, Caroline
    Tu, Yaoquan
    Ågren, Hans
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    HULIS in Nanoaerosol Clusters; Investigations of Surface Tension and Aggregate Formation using Molecular Dynamics Simulations2011Ingår i: Atmospheric Chemistry and Physics Discussions, ISSN 1680-7367, E-ISSN 1680-7375Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    Cloud condensation nuclei act as cores for water vapor condensation, and their composition and chemical properties may enhance or depress the ability for droplet growth. In this study we use molecular dynamics simulations to show that humic-like substances of larger systems (8.6 nm in diameter) mimic experimental data well referring to reduction of surface tension. The structural properties examined show the ability for the humic-like substances to aggregate inside the nanoaerosol clusters.

  • 28. Hong, Tao
    et al.
    Song, Heli
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Zhang, Weibing
    Xie, Yongshu
    Syntheses of mono- and diacylated bipyrroles with rich substitution modes and development of a prodigiosin derivative as a fluorescent Zn(II) probe2014Ingår i: RSC Advances, E-ISSN 2046-2069, Vol. 4, nr 12, s. 6133-6140Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The acylation of 2,20-bipyrrole with pentafluorobenzoyl chloride in the presence of AlCl3 afforded six acylated products with rich alpha-, beta-, beta(1)-, alpha,alpha'-, alpha,beta(')-, and alpha,beta(1)'-substitution modes for 1-6, respectively. Then, the alpha,alpha'-diacylated compound 4 was used to synthesize a prodigiosin derivative 9, which provides an alternative method for the syntheses of prodigiosin derivatives. Crystal structures of 1, 4 and 9 show interesting supramolecular dimers formed by multiple hydrogen bonds, O...pi interactions, as well as pi... pi interactions. Interestingly, 9 shows fluorescence turn-on probing behavior towards Zn2+ both in DMF and in DMF-HEPES, with high sensitivity and selectivity. The detection limit for Zn2+ in DMF was calculated to be 1.1 x 10(-8) M.

  • 29.
    Hua, Weijie
    et al.
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Tian, Guangjun
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Fronzoni, Giovanna
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Stener, Mauro
    Luo, Yi
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Fe L-Edge X-ray Absorption Spectra of Fe(II) Polypyridyl Spin Crossover Complexes from Time-Dependent Density Functional Theory2013Ingår i: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 117, nr 51, s. 14075-14085Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    L-edge near-edge X-ray fine structure spectroscopy (NEXAFS) has become a powerful tool to study the electronic structure and dynamics of metallo-organic and biological compounds in solution. Here, we present a series of density functional theory calculations of Fe L-edge NEXAFS for spin crossover (SCO) complexes within the time-dependent framework. Several key factors that control the L-edge excitations have been carefully examined using an Fe(II) polypyridyl complex [Fe(tren(py)(3))](2+) (where tren(py)(3) = tris(2-pyridylmethyliminoethyl)amine) as a model system. It is found that the electronic spectra of the low-spin (LS, singlet), intermediate-spin (IS, triplet), and high-spin (HS, quintet) states have distinct profiles. The relative energy positions, but not the spectral profiles, of different spin states are sensitive to the choice of the functionals. The inclusion of the vibronic coupling leads to almost no visible change in the resulting NEXAFS spectra because it is governed only by low-frequency modes of less than 500 cm(-1). With the help of the molecular dynamics sampling in acetonitrile at 300 K, our calculations reveal that the thermal motion can lead to a noticeable broadening of the spectra. The main peak position is strongly associated with the length of the Fe-N bond.

  • 30. Jana, Avijit
    et al.
    Bai, Linyi
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Ågren, Hans
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Zhao, Yanli
    Morphology Tuning of Self-Assembled Perylene. Monoimide from Nanoparticles to Colloidosomes with Enhanced Excimeric NIR Emission for Bioimaging2016Ingår i: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 8, nr 3, s. 2336-2347Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Organic near-infrared (NIR) fluorescent probes have been recognized as an emerging class of materials exhibiting a great potential in advanced bioanalytical applications. However, synthesizing such organic probes that could simultaneously work in the NIR spectral range and have large Stokes shift, high stability in biological systems, and high photostability have been proven challenging. In this work, aggregation induced excimeric NIR emission in aqueous media was observed from a suitably substituted perylene monoimide (PeIm) dye. Controlled entrapment of the dye into pluronic F127 micellar system to preserve its monomeric green emission in aqueous media was also established. The aggregation process of the PeIm dye to form organic nanoparticles (NPs) was evaluated experimentally by the means of transmission electron microscope imaging as well as theoretically by the molecular dynamics simulation studies. Tuning the morphology along with the formation of colloidosomes by the controlled self-aggregation of PeIm NPs in aqueous suspension was demonstrated successfully. Finally, both excimeric and monomeric emissive PeIm NPs as well as PeIm colloidosomes were employed for the bioimaging in vitro.

  • 31. Jana, Avijit
    et al.
    Nguyen, Kim Truc
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Zhu, Pengcheng
    Tan, Nguan Soon
    Ågren, Hans
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Zhao, Yanli
    Perylene-Derived Single-Component Organic Nanoparticles with Tunable Emission: Efficient Anticancer Drug Carriers with Real-Time Monitoring of Drug Release2014Ingår i: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 8, nr 6, s. 5939-5952Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An organic nanoparticle-based drug delivery system with high drug loading efficacy (similar to 79 wt %) was developed using a perylene-derived photoremovable protecting group, namely, perylene-3,4,9,10-tetrayltetramethanol (Pe(OH)(4)). The anticancer drug chlorambucil was protected by coupling with Pe(OH)(4) to form photocaged nanoparticles (Pe(OH)(4)). The photorelease mechanism of chlorambucil from the Pe(Cbl)(4) conjugate was investigated experimentally by high-resolution mass spectrometry and theoretically by density functional theory calculations. The Pe(Cbl)(4) nanoparticles perform four important roles: (i) a nanocarrier for drug delivery, (ii) a phototrigger for drug release, (iii) a fluorescent chromophore for cell imaging, and (iv) a photoswitchable fluorophore for real-time monitoring of drug release. Tunable emission of the perylene-derived nanoparticles was demonstrated by comparing the emission properties of the Pe(OH)(4) and Pe(Cbl)(4) nanoparticles with perylene-3-ylmethanol. These nanoparticles were subsequently employed in cell imaging for investigating their intracellular localization. Furthermore, the in vivo toxicity of the Pe(OH)(4) nanoparticles was investigated using the mouse model. Histological tissue analysis of five major organs, i.e., heart, kidney, spleen, liver, and lung, indicates that the nanoparticles did not show any obvious damage to these major organs under the experimental conditions. The current research presents a successful example of integrating multiple functions into single-component organic nanoparticles for drug delivery.

  • 32. Jiang, Tao
    et al.
    Li, Dongyu
    Hang, Yandi
    Gao, Yuting
    Zhang, Hequn
    Zhao, Xinyuan
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Li, Bo
    Qian, Jun
    Hua, Jianli
    Tetraphenylethene end-capped diketopyrrolopyrrole fluorogens with AIE and large two-photon absorption cross-sections features and application in bioimaging2016Ingår i: Dyes and pigments, ISSN 0143-7208, E-ISSN 1873-3743, Vol. 133, s. 201-213Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work, a series of new diketopyrrolopyrrole-based dyes have been synthesized by connecting tetraphenylethene to the diketopyrrolopyrrole core. All the four compounds exhibit good aggregation induced emission property with nonemissive in the solution but strong red fluorescence in the aggregate or solid state. Also, these new dyes exhibit large two-photon absorption cross sections (a), in which the a data measured by the open aperture Z-scan technique are determined to be 150, 300, 1140 and 1016 GM for four dyes, respectively. In addition, compound with stilbene and four tetraphenylethene units (DPP-TPE-3) was used as the luminogen and encapsulated into nanoparticles for cell imaging and two-photon excited fluorescence blood vessels imaging. The result indicates that it can be used as the effective fluorescence probe for bioimaging and has great potential for bioapplications. (C) 2016 Elsevier Ltd. All rights reserved.

  • 33.
    Kang, Yu
    et al.
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Tu, Yaoquan
    Wang, Qi
    Ågren, Hans
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    On the Mechanism of Protein Adsorption onto Hydroxylated and Nonhydroxylated TiO2 Surfaces2010Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 114, nr 34, s. 14496-14502Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Protein adsorption onto implant surfaces is of great importance for the regulation of implant bioactivity. Surface modification of implants is a promising way in the molecular design of biocompatible materials against nonspecific adsorption of proteins. On the basis of these fundamental facts, we focus in this work on the different behavior of protein adsorption on hydroxylated and nonhydroxylated rutile TiO2 (110) surfaces through molecular dynamics simulations. Our investigation indicates that the distribution of the water molecules at the interface induced by the surface modification plays an important role in the protein adsorption. The surface with modified hydroxyl groups was observed to have much greater affinity to the protein, as reflected by the larger protein-surface electrostatic interaction and by the larger amount of adsorbed residues. The highly ordered structure of the modified hydroxyl groups on the hydroxylated surface diminishes the possibility of hydrogen bond formation between the surface and the water molecules above it, which in turn makes it easier for the protein to move closer to the surface with hydroxyl modification.

  • 34. Kapilashrami, Mukes
    et al.
    Wang, Yung Jui
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Glans, Per-Anders
    Fang, Mei
    Riazanova, Anastasia
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Belova, Lyubov M.
    Rao, K. Venkat
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Luo, Yi
    Barbiellini, Bernardo
    Lin, Hsin
    Markiewicz, Robert
    Bansil, Arun
    Hussain, Zahid
    Guo, Jinghua
    Understanding the magnetic interaction between intrinsic defects and impurity ions in room-temperature ferromagnetic Mg1-xFexO thin films2016Ingår i: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 28, nr 15, artikel-id 156002Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Understanding the nature and characteristics of the intrinsic defects and impurities in the dielectric barrier separating the ferromagnetic electrodes in a magnetic tunneling junction is of great importance for understanding the often observed 'barrier-breakdown' therein. In this connection, we present herein systematic experimental (SQUID and synchrotron-radiation-based x-ray absorption spectroscopy) and computational studies on the electronic and magnetic properties of Mg1-xFexO thin films. Our studies reveal: (i) defect aggregates comprised of basic and trimer units (Fe impurity coupled to 1 or 2 Mg vacancies) and (ii) existence of two competing magnetic orders, defect- and dopant-induced, with spin densities aligning anti-parallel if the trimer is present in the oxide matrix. These findings open up new avenues for designing tunneling barriers with high endurance and tunneling effect upon tuning the concentration/distribution of the two magnetic orders.

  • 35. Kong, Jiahui
    et al.
    Li, Qizhao
    Li, Minzhi
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Liang, Xu
    Zhu, Weihua
    Ågren, Hans
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Xie, Yongshu
    Modulation of the structures and properties of bidipyrrin zinc complexes by introducing terminal alpha-methoxy groups2017Ingår i: Dyes and pigments, ISSN 0143-7208, E-ISSN 1873-3743, Vol. 137, s. 430-436Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A bidipyrrin nickel complex was synthesized in a high yield by oxidatively coupling between the ligands in the corresponding 2:1 (L:M) type of dipyrrin nickel complex, and further demetallation afforded the free bidipyrrin ligand. Interestingly, when treating the bidipyrrin nickel complex or the free bidipyrrin with FeCl3 in CH2Cl2/MeOH, the symmetric di-alpha-methoxy bidipyrrin could be synthesized in a high yield, with two methoxy groups attached to the terminal pyrrolic alpha-positions. Moreover, the coordination of the unsubstituted and disubstituted bidipyrrins with Zn(OAc)(2),2H(2)O afforded two similar M2L2 type of bidipyrrin helical complexes with different ligand conformations and different Zn center dot center dot center dot Zn distances of 5.353 and 3.357 angstrom, respectively. The difference in the conformations may be related to the electrostatic repulsions between the methoxy substituents. These results indicate that the dyes based on helical bidipyrrin zinc complexes with tunable structures and photophysical properties may be developed simply by modulating the terminal alpha-substituents.

  • 36. Kong, Jiahui
    et al.
    Zhang, Qiong
    Savage, Mathew
    Li, Minzhi
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Yang, Sihai
    Liang, Xu
    Zhu, Weihua
    Ågren, Hans
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Xie, Yongshu
    Tetra- and Octapyrroles Synthesized from Confusion and Fusion Approaches2016Ingår i: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 18, nr 19, s. 5046-5049Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    By oxidation of an alternately N-confused bilane in CH2Cl2, a C-N fused tetrapyrrin was synthesized that bears a 5.5.5-tricyclic ring generated from an intramolecular C-N linkage. When CH3CN was used as the reaction medium, a multiply C-N-fused octapyrrolic dimer was also obtained that contained two 5.5.5.7.5-pentacyclic moieties and a bipyrrole unit generated from the intramolecular C-N linkage and intermolecular C-C linkage, respectively. This could be coordinated with Ni(acac)(2) to afford a mixed-ligand complex.

  • 37.
    Li, Chengjie
    et al.
    East China Univ Sci & Technol, Joint Int Res Lab Precis Chem & Mol Engn, Feringa Nobel Prize Scientist Joint Res Ctr,Sch C, Shanghai Key Lab Funct Mat Chem,Key Lab Adv Mat, Shanghai 200237, Peoples R China..
    Zhang, Kai
    East China Univ Sci & Technol, Joint Int Res Lab Precis Chem & Mol Engn, Feringa Nobel Prize Scientist Joint Res Ctr,Sch C, Shanghai Key Lab Funct Mat Chem,Key Lab Adv Mat, Shanghai 200237, Peoples R China..
    Ishida, Masatoshi
    Kyushu Univ, Dept Chem & Biochem, Grad Sch Engn, Ctr Mol Syst, Fukuoka 8190395, Japan..
    Li, Qizhao
    East China Univ Sci & Technol, Joint Int Res Lab Precis Chem & Mol Engn, Feringa Nobel Prize Scientist Joint Res Ctr,Sch C, Shanghai Key Lab Funct Mat Chem,Key Lab Adv Mat, Shanghai 200237, Peoples R China..
    Shimomura, Keito
    Kyushu Univ, Dept Chem & Biochem, Grad Sch Engn, Ctr Mol Syst, Fukuoka 8190395, Japan..
    Baryshnikov, Gleb V.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Li, Xin
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, Parallelldatorcentrum, PDC.
    Savage, Mathew
    Univ Manchester, Sch Chem, Manchester M13 9PL, Lancs, England..
    Wu, Xin-Yan
    East China Univ Sci & Technol, Joint Int Res Lab Precis Chem & Mol Engn, Feringa Nobel Prize Scientist Joint Res Ctr,Sch C, Shanghai Key Lab Funct Mat Chem,Key Lab Adv Mat, Shanghai 200237, Peoples R China..
    Yang, Sihai
    Univ Manchester, Sch Chem, Manchester M13 9PL, Lancs, England..
    Furuta, Hiroyuki
    Kyushu Univ, Dept Chem & Biochem, Grad Sch Engn, Ctr Mol Syst, Fukuoka 8190395, Japan..
    Xie, Yongshu
    East China Univ Sci & Technol, Joint Int Res Lab Precis Chem & Mol Engn, Feringa Nobel Prize Scientist Joint Res Ctr,Sch C, Shanghai Key Lab Funct Mat Chem,Key Lab Adv Mat, Shanghai 200237, Peoples R China..
    Tripyrrin-armed isosmaragdyrins: synthesis, heterodinuclear coordination, and protonation-triggered helical inversion2020Ingår i: Chemical Science, ISSN 2041-6520, E-ISSN 2041-6539, Vol. 11, nr 10, s. 2790-2795Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Oxidative ring closure of linear oligopyrroles is one of the synthetic approaches to novel porphyrinoids with dinuclear coordination sites and helical chirality. The spatial arrangement of the pyrrolic groups of octapyrrole (P8) affected the position of the intramolecular oxidative coupling of the pyrrolic units; tripyrrin-armed isosmaragdyrin analogue (1) containing a beta,beta-linked bipyrrole moiety was synthesized regioselectively in a high yield by using FeCl3. Ni-II-coordination at the armed tripyrrin site of 1 allowed the formation of diastereomeric helical twisted complexes (2A and 2B) and succeeding Cu-II-coordination at the macrocyclic core afforded heterodinuclear Ni-II/Cu-II-complexes (3A and 3B). Each of them comprised a pair of separable enantiomers, exhibiting P- and M-helices, respectively. Notably, diastereomeric interconversion from 2A to 2B was quantitatively achieved as a consequence of helical transformation under acidic conditions.

  • 38. Li, Hong
    et al.
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Cao, Zhan-Qi
    Qu, Da-Hui
    Ågren, Hans
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Tian, He
    A Switchable bis-Branched [1]Rotaxane featuring Dual-Mode Molecular Motions and Tunable Molecular Aggregation2014Ingår i: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 6, nr 21, s. 18921-18929Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A multifunctional bis-branched [1]rotaxane containing a perylene bisimide (PBI) core and two identical bistable[1]rotaxane arms terminated with ferrocene units was prepared and characterized by H-1 NMR, C-13 NMR, and 2D ROESY NMR spectroscopies and by HR-ESI spectrometry. The system is shown to possess several key features: (1) In acetone solution, external acid base stimuli can result in relative mechanical movements of its ring and thread, which can induce extension and contraction movements of the whole system accompanied by a rotational movement of the ferrocene units, thus realizing dual-mode molecular motions, and the optimized conformations at different states are obtained through molecular dynamics simulations employing the general Amber force field. (2) The introduction of PBI enables the system fluorescence encoding through distance-dependent photoinduced electron transfer process from the ferrocene units to the PBI fluorophore. (3) The addition of Zn2+ can increase the degree of aggregation of the system, while adding base hinders aggregation because of the movement of the macrocyde. The tunable aggregated nanostructural morphologies of [1]rotaxane were examined by scanning electron microscopy. These results can pave the way to achieve precise control of integrated and coupling nanomechanical motions at a single-molecule level and provide more insight into controlling the aggregate behavior of switchable mechanically interlocked molecules.

  • 39. Li, Hong
    et al.
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Wu, Ying
    Ågren, Hans
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Qu, Da-Hui
    A Musclelike [2](2)Rotaxane: Synthesis, Performance, and Molecular Dynamics Simulations2014Ingår i: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 79, nr 15, s. 6996-7004Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A novel bistable symmetric [2](2)rotaxane was prepared by a threading-followed-by-stoppering strategy and characterized with H-1, C-13, and 2D ROESY NMR spectroscopy and HR-ESI spectrometry. The symmetric [2] (2)rotaxane system consists of an anthracene-based bis(crown ether) as macrocycles, and each of the two dibenzo[24]crown-8 (DB24C8) rings is threaded by the pendant substituents a symmetrically substituted central rotatable ferrocene subunit that possesses two distinguishable recognition sites for the DB24C8 ring: namely, a dibenzylammonium site and an N-methyltriazolium site. The uniform shuttling motion of the thread relative to the two DB24C8 rings in [2](2)rotaxane can be driven by external acid base stimuli, which was evidenced by H-1 and 2D ROESY NMR spectroscopy. Furthermore, molecular dynamics simulations of the [2](2)rotaxane were carried out both in protonated (stretched) and in neutral (contracted) forms. The calculated percentage change in molecular length of the [2](2)rotaxane between the two end-capping bis(methoxyl)phenyl groups is about 48% in the two different states (in acetone), which is much larger than the percentage change (similar to 27%) in human muscle. Moreover, in the two states, the C*-Cp-Cp-C* dihedral angles are computed as -177 degrees in the stretched state and -112 degrees in the contracted state, indicating a correlation between the translational and rotational motions of the [2](2)rotaxane.

  • 40. Li, Hong
    et al.
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Ågren, Hans
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Qu, Da-Hui
    Two Switchable Star-Shaped [1](n)Rotaxanes with Different Multibranched Cores2014Ingår i: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 16, nr 18, s. 4940-4943Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Two novel star-shaped [1](n)rotaxanes with three and four identical [1]rotaxane arms but different multibranched cores were designed, synthesized, and well-characterized. In the two systems, external base acid stimuli result in the uniform relative mechanical movement of the macrocydic rings and threads of their [1]rotaxane arms. The energy-minimized structures of the two rotaxanes in different states were obtained using molecular dynamics simulations in acetone solution, suggesting the construction of more sophisticated molecular machines mimicking the extension and contraction motions.

  • 41.
    Li, Qizhao
    et al.
    East China Univ Sci & Technol, Key Lab Adv Mat, Feringa Nobel Prize Scientist Joint Res Ctr, Sch Chem & Mol Engn, 130 Meilong Rd, Shanghai 200237, Peoples R China.;East China Univ Sci & Technol, Joint Int Res Lab Precis Chem & Mol Engn, Feringa Nobel Prize Scientist Joint Res Ctr, Sch Chem & Mol Engn, 130 Meilong Rd, Shanghai 200237, Peoples R China..
    Ishida, Masatoshi
    Kyushu Univ, Dept Chem & Biochem, Grad Sch Engn, Fukuoka 8190395, Japan.;Kyushu Univ, Ctr Mol Syst, Fukuoka 8190395, Japan..
    Kai, Hiroto
    Kyushu Univ, Dept Chem & Biochem, Grad Sch Engn, Fukuoka 8190395, Japan.;Kyushu Univ, Ctr Mol Syst, Fukuoka 8190395, Japan..
    Gu, Tingting
    Jiangsu Univ, Sch Chem & Chem Engn, Zhenjiang 212013, Jiangsu, Peoples R China..
    Li, Chengjie
    East China Univ Sci & Technol, Key Lab Adv Mat, Feringa Nobel Prize Scientist Joint Res Ctr, Sch Chem & Mol Engn, 130 Meilong Rd, Shanghai 200237, Peoples R China.;East China Univ Sci & Technol, Joint Int Res Lab Precis Chem & Mol Engn, Feringa Nobel Prize Scientist Joint Res Ctr, Sch Chem & Mol Engn, 130 Meilong Rd, Shanghai 200237, Peoples R China..
    Li, Xin
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, Parallelldatorcentrum, PDC. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Baryshnikov, Glib
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Liang, Xu
    Jiangsu Univ, Sch Chem & Chem Engn, Zhenjiang 212013, Jiangsu, Peoples R China..
    Zhu, Weihua
    Jiangsu Univ, Sch Chem & Chem Engn, Zhenjiang 212013, Jiangsu, Peoples R China..
    Ågren, Hans
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi. KTH Royal Inst Technol, Dept Theoret Chem & Biol, Sch Biotechnol, S-10691 Stockholm, Sweden..
    Furuta, Hiroyuki
    Kyushu Univ, Dept Chem & Biochem, Grad Sch Engn, Fukuoka 8190395, Japan.;Kyushu Univ, Ctr Mol Syst, Fukuoka 8190395, Japan..
    Xie, Yongshu
    East China Univ Sci & Technol, Key Lab Adv Mat, Feringa Nobel Prize Scientist Joint Res Ctr, Sch Chem & Mol Engn, 130 Meilong Rd, Shanghai 200237, Peoples R China.;East China Univ Sci & Technol, Joint Int Res Lab Precis Chem & Mol Engn, Feringa Nobel Prize Scientist Joint Res Ctr, Sch Chem & Mol Engn, 130 Meilong Rd, Shanghai 200237, Peoples R China..
    Skeletal Rearrangement of Twisted Thia-Norhexaphyrin: Multiply Annulated Polypyrrolic Aromatic Macrocycles2019Ingår i: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 58, nr 18, s. 5925-5929Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A hybrid thia-norhexaphyrin comprising a directly linked N-confused pyrrole and thiophene unit (1) revealed unique macrocycle transformations to afford multiply inner-annulated aromatic macrocycles. Oxidation with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone triggered a cleavage of the C-S bond of the thiophene unit, accompanied with skeletal rearrangement to afford unique pi-conjugated products: a thiopyrrolo-pentaphyrin embedded with a pyrrolo[1,2]isothiazole (2), a sulfur-free pentaphyrin incorporating an indolizine moiety (3), and a thiopyranyltriphyrinoid containing a 2H-thiopyran unit (4). Furthermore, 2 underwent desulfurization reactions to afford a fused pentaphyrin containing a pyrrolizine moiety (5) under mild conditions. Using expanded porphyrin scaffolds, oxidative thiophene cleavage and desulfurization of the hitherto unknown N-confused core-modified macrocycles would be a practical approach for developing unique polypyrrolic aromatic macrocycles.

  • 42. Li, T.
    et al.
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Wang, J.
    Ågren, Hans
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Ma, X.
    Tian, H.
    Photoresponsive Supramolecular Assemblies Based on a C3-Symmetric Benzene-1,3,5-tricarboxamide Anchored Diarylethene2016Ingår i: Advanced Optical Materials, ISSN 2195-1071Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A functional C3-symmetric benzene-1,3,5-tricarboxamide-anchored diarylethene molecule (C3-BTE) is synthesized, which evolves into ordered superstructures with tunable morphology properties both in different solvent and via alternative light stimuli. The formation of rod-like assemblies from C3-BTE is reported and the self-assembly property of C3-BTE can be realized through alternative light stimuli in nonpolar solvents such as toluene.

  • 43. Li, T.
    et al.
    Li, Xin
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, Parallelldatorcentrum, PDC. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Wang, J.
    Ågren, Hans
    KTH, Skolan för bioteknologi (BIO), Centra, Albanova VinnExcellence Center for Protein Technology, ProNova. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Ma, X.
    Tian, H.
    Supramolecular Assemblies: Photoresponsive Supramolecular Assemblies Based on a C3-Symmetric Benzene-1,3,5-tricarboxamide-Anchored Diarylethene (Advanced Optical Materials 6/2016)2016Ingår i: Advanced Optical Materials, ISSN 2162-7568, E-ISSN 2195-1071, Vol. 4, nr 6Artikel i tidskrift (Refereegranskat)
  • 44. Li, Wenlong
    et al.
    Cai, Yunsong
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Ågren, Hans
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Tian, He
    Zhu, Wei-Hong
    Sterically hindered diarylethenes with a benzobis(thiadiazole) bridge: photochemical and kinetic studies2015Ingår i: Journal of Materials Chemistry C, ISSN 2050-7526, E-ISSN 2050-7534, Vol. 3, nr 33, s. 8665-8674Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Four rationally designed diarylethenes (DAEs) 1-4 with a benzobis(thiadiazole) bridge are specifically designed for gaining insights into steric effects on photochromic performances. It is shown that, upon increasing steric hindrance, the exchanging rate between two main conformers in the ring-open form gradually slows down, offering the opportunity for isolating photoactive anti-parallel conformers. Impressively, the separated anti-parallel conformer shows high cyclization quantum yields over the unresolved common DAEs. The typical donor-pi-acceptor (D-pi-A) feature in ring-open DAEs 1-4 endows their prominent fluorescence, which can be conveniently modulated by photocyclization. In the ring-closed form, the excess steric hindrance is found to seriously disrupt the thermal bistability, and particularly 3c fades quickly with a half-life of several hours at ambient temperature. In contrast, both 1c and 2c exhibit excellent stability, which originates from the stabilization effects of intramolecular hydrogen bonds. This work demonstrates the steric effects on the photochemical and kinetic behaviors of DAEs, providing a unique approach to develop photochromic DAEs with high photosensitivity.

  • 45. Li, Wenlong
    et al.
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Xie, Yongshu
    Wu, Yue
    Li, Mengqi
    Wu, Xin-Yan
    Zhu, Wei-Hong
    Tian, He
    Enantiospecific photoresponse of sterically hindered diarylethenes for chiroptical switches and photomemories2015Ingår i: Scientific Reports, E-ISSN 2045-2322, Vol. 5, artikel-id 9186Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Light-driven transcription, replication and enzyme catalysis are critically dependent upon a delicate transfer between molecular and supramolecular chirality. Chemists have well realized the impressive stereospecificity over many thermally accessible cycloaddition with chiral catalysts, but making light work in the enantiomer control of diarylethene photocyclization has proved to be more challenging. Here, we report a unique sterically hindered diarylethene (BBTE) system with absolute enantiospecific photocyclization and cycloreversion. Moreover, we have fully separated all the five thermally stable isomers, consisting of one achiral parallel conformer, one pair of anti-parallel ring-open enantiomers, and another pair of ring-closed enantiomers, whose absolute chiral configurations are entirely elucidated by single X-ray crystallographic analyses. The photo-responsive feature exhibits a reversible, complete enantio-control transformation without racemism, offering an unrivaled unimolecular enantiospecific platform for potential applications as bistable chiroptical switches and all-photonic photomemories with optical rotation as non-destructive readout.

  • 46. Li, X.
    et al.
    Baryshnikov, Gleb V.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Ding, L.
    Bao, X.
    Li, Xin
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Liu, M.
    Shen, S.
    Luo, M.
    Zhang, M.
    Ågren, Hans
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi. College of Chemistry and Chemical Engineering, Department of Chemistry, Henan University, Kaifeng, Henan 475004, China.
    Wang, X.
    Zhu, L.
    Dual-Phase Thermally Activated Delayed Fluorescence Luminogens: A Material for Time-Resolved Imaging Independent of Probe Pretreatment and Probe Concentration2020Ingår i: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 59, nr 19, s. 7548-7554Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Developing luminescent probes with long lifetime and high emission efficiency is essential for time-resolved imaging. However, the practical applications usually suffer from emission quenching of traditional luminogens in aggregated states, or from weak emission of aggregation-induced emission type luminogens in monomeric states. Herein, we overcome this dilemma by a rigid-and-flexible alternation design in donor–acceptor–donor skeletons, to achieve a thermally activated delayed fluorescence luminogen with high emission efficiency both in the monomeric state (quantum yield up to 35.3 %) and in the aggregated state (quantum yield up to 30.8 %). Such a dual-phase strong and long-lived emission allows a time-resolved luminescence imaging, with an efficiency independent of probe pretreatment and probe concentration. The findings open opportunities for developing luminescent probes with a usage in larger temporal and spatial scales.

  • 47.
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Applications of Molecular Dynamics in Atmospheric and Solution Chemistry2011Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    This thesis focuses on the applications of molecular dynamics simulation techniques in the fields of solution chemistry and atmospheric chemistry. The work behind the thesis takes account of the fast development of computer hardware, which has made computationally intensive simulations become more and more popular in disciplines like pharmacy, biology and materials science. In molecular dynamics simulations using classical force fields, the atoms are represented by mass points with partial charges and the inter-atomic interactions are modeled by approximate potential functions that produce satisfactory results at an economical computational cost. The three-dimensional trajectory of a many-body system is generated by integrating Newton’s equations of motion, and subsequent statistical analysis on the trajectories provides microscopic insight into the physical properties of the system.

    The applications in this thesis of molecular dynamics simulations in solution chemistry comprise four aspects: the 113Cd nuclear magnetic resonance shielding constant of aqua Cd(II) ions, paramagnetic 19F nuclear magnetic resonance shift in fluorinated cysteine, solvation free energies and structures of metal ions, and protein adsorption onto TiO2. In the studies of nuclear magnetic resonance parameters, the relativistic effect of the 113Cd nucleus and the paramagnetic shift of 19F induced by triplet O2 are well reproduced by a combined molecular dynamics and density functional theory approach. The simulation of the aqua Cd(II) ion is also extended to several other monovalent, divalent and trivalent metal ions, where careful parameterization of the metal ions ensures the reproduction of experimental solvation structures and free energies. Molecular dynamics simulations also provided insight into the mechanism of protein adsorption onto the TiO2 surface by suggesting that the interfacial water molecules play an important role of mediating the adsorption and that the hydroxylated TiO2 surface has a large affinity to the proteins.

    The applications of molecular dynamics simulations in atmospheric chemistry are mainly focused on two types of organic components in aerosol droplets: humic-like compounds and amino acids. The humic-like substances, including cis-pinonic acid, pinic acid and pinonaldehyde, are surface-active organic compounds that are able to depress the surface tension of water droplets, as revealed by both experimental measurements and theoretical computations. These compounds either concentrate on the droplet surface or aggregate inside the droplet. Their effects on the surface tension can be modeled by the Langmuir-Szyszkowski equation. The amino acids are not strong surfactants and their influence on the surface tension is much smaller. Simulations show that the zwitterionic forms of serine, glycine and alanine have hydrophilic characteristics, while those of valine, methionine and phenylalanine are hydrophobic. The curvature dependence of the surface tension is also analyzed, and a slight improvement in the Köhler equation is obtained by introducing surface tension corrections for droplets containing glycine and serine.

    Through several examples it is shown that molecular dynamics simulations serve as a promising tool in the study of aqueous systems. Both solute-solvent interactions and interfaces can be treated properly by choosing suitable potential functions and parameters. Specifically, molecular dynamics simulations provide a microscopic picture that evolves with time, making it possible to follow the dynamic processes such as protein adsorption or atmospheric droplet formation. Moreover, molecular dynamics simulations treat a large number of molecules and give a statistical description of the system; therefore it is convenient to compare the simulated results with experimentally measured data. The simulations can provide hints for better design of experiments, while experimental data can be fed into the refinement of the simulation model. As an important complementary to experiments, molecular dynamics simulations will continue to play significant roles in the research fields of physics, chemistry, materials science, biology and medicine.

    Ladda ner fulltext (pdf)
    FULLTEXT01
  • 48.
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Theoretical studies on electronic structure and x-ray spectroscopies of 2D materials2016Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Extraordinary chemical and physical properties have been discovered from the studies of two-dimensional (2D) materials, ever since the successful exfoliation of graphene, the first 2D material. Theoretical investigations of electronic structure and spectroscopies of these materials play a fundamental role in deep understanding the various properties. In particular, the band structure and near-edge x-ray absorption fine structure (NEXAFS) spectroscopy can provide critical information near the Fermi level. In this thesis, we performed first-principles density functional theory calculations to study the electronic structure and NEXAFS spectra of four materials, including three 2D materials and one bulk material. The three 2D materials are atomically thin bismuth telluride, nitrogen and boron nitride doped graphenes. The bulk material is lithium intercalated graphite, an analogue of lithium doped graphene. Our studies provide important electronic property information of the studied materials, and are helpful for understanding their properties and developing potential applications.

    Ladda ner fulltext (pdf)
    fulltext
  • 49.
    Li, Xin
    et al.
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Carravetta, Vincenzo
    Li, Cui
    Monti, Susanna
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi. CNR-ICCOM, Italy .
    Rinkevicius, Zilvinas
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Ågren, Hans
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Optical Properties of Gold Nanoclusters Functionalized with a Small Organic Compound: Modeling by an Integrated Quantum-Classical Approach2016Ingår i: Journal of Chemical Theory and Computation, ISSN 1549-9618, E-ISSN 1549-9626, Vol. 12, nr 7, s. 3325-3339Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Motivated by the growing importance of organometallic nanostructured materials and nanoparticles as microscopic devices for diagnostic and sensing applications, and by the recent considerable development in the simulation of such materials, we here choose a prototype system para-nitroaniline (pNA) on gold nanoparticles to demonstrate effective strategies for designing metal nanoparticles with organic conjugates from fundamental principles. We investigated the motion, adsorption mode, and physical chemistry properties of gold-pNA particles, increasing in size, through classical molecular dynamics (MD) simulations in connection with quantum chemistry (QC) calculations. We apply the quantum mechanics-capacitance molecular mechanics method [Z. Rinkevicius et al. J. Chem. Theory Comput. 2014, 10, 989] for calculations of the properties of the conjugate nanoparticles, where time dependent density functional theory is used for the QM part and a capacitance-polarizability parametrization of the MM part, where induced dipoles and charges by metallic charge transfer are considered. Dispersion and short-range repulsion forces are included as well. The scheme is applied to one- and two-photon absorption of gold-pNA clusters increasing in size toward the nanometer scale. Charge imaging of the surface introduces red-shifts both because of altered excitation energy dependence and variation of the relative intensity of the inherent states making up for the total band profile. For the smaller nanoparticles the difference in the crystal facets are important for the spectral outcome which is also influenced by the surrounding MM environment.

  • 50.
    Li, Xin
    et al.
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Hede, T.
    Tu, Y.
    Leck, C.
    Ågren, Hans
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Glycine in aerosol water droplets: a critical assessment of Köhler theory by predicting surface tension from molecular dynamics simulations2011Ingår i: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 11, nr 2, s. 519-527Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Aerosol particles in the atmosphere are important participants in the formation of cloud droplets and have significant impact on cloud albedo and global climate. According to the Kohler theory which describes the nucleation and the equilibrium growth of cloud droplets, the surface tension of an aerosol droplet is one of the most important factors that determine the critical supersaturation of droplet activation. In this paper, with specific interest to remote marine aerosol, we predict the surface tension of aerosol droplets by performing molecular dynamics simulations on two model systems, the pure water droplets and glycine in water droplets. The curvature dependence of the surface tension is interpolated by a quadratic polynomial over the nano-sized droplets and the limiting case of a planar interface, so that the so-called Aitken mode particles which are critical for droplet formation could be covered and the Kohler equation could be improved by incorporating surface tension corrections.

123 1 - 50 av 145
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf