Ändra sökning
Avgränsa sökresultatet
12 1 - 50 av 82
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • harvard1
  • 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. Ahlberg, P.
    et al.
    Karlsson, A.
    Goeppert, A.
    Lill, S. O. N.
    Dinér, Peter
    Sommer, J.
    Solvated CH5+ in liquid superacid2001Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 7, nr 12, s. 2501-2510Artikel i tidskrift (Refereegranskat)
  • 2.
    Ahlquist, Mårten
    et al.
    Technical University of Denmark.
    Nielsen, T E
    Le Quement, S
    Tanner, David
    Technical University of Denmark.
    Norrby, Per-Ola
    Technical Univeristy of Denmark.
    An experimental and theoretical study of the mechanism of stannylcupration of alpha, beta-acetylenic ketones and esters2006Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 12, nr 10, s. 2866-2873Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The title reaction has been investigated by experimental and computational (DFT) techniques, and subsequently compared to the corresponding carbocupration reaction, with particular emphasis oil the stereoselectivity. For stannylcupration of an ynone substrate, only the anti-addition product is observed, whereas for the corresponding ynoate substrate, the stereoselectivity can be affected by the reaction conditions: in the presence of methanol as proton donor, the initial syn-addition product can be trapped, whereas a syn/anti mixture is obtained in a non-protic solvent. This is in sharp contrast to the carbocupration of the same ynone substrate with a cyanocuprate (RCu(CN)Li), which is highly selective for syn-addition. The product selectivities can be understood from a detailed computational characterization of the reaction paths, and in particular from the relative stabilities of the vinyl cuprate and allenolate intermediates. It is suggested that the stereodetermining step is protonation of vinyl cuprate intermediates.

  • 3. Ahlstrand, David A.
    et al.
    Polukeev, Alexey V.
    Marcos, Rocio
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Ahlquist, Mårten S. G.
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Wendt, Ola F.
    Csp(3)-H Activation without Chelation Assistance in an Iridium Pincer Complex Forming Cyclometallated Products2017Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 23, nr 8, s. 1748-1751Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cyclometallation of 8-methylquinoline and 2-(dimethylamino)-pyridine in an iridium-based pincer complex is described. The C-H activation of 2-(dimethylamino) pyridine is not chelation assisted, which has not been described before for Csp(3)-H bonds in cyclometallation reactions. The mechanism of the cyclometallation of 2-(dimethylamino) pyridine was studied by DFT calculations and kinetic measurements.

  • 4. Amorati, Riccardo
    et al.
    Valgimigli, Luca
    Dinér, Peter
    Bakhtiari, Khadijeh
    Saeedi, Mina
    Engman, Lars
    Multi-faceted reactivity of alkyltellurophenols towards peroxyl radicals: Catalytic antioxidant versus thiol-depletion effect2013Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 19, nr 23, s. 7510-7522Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Hydroxyaryl alkyl tellurides are effective antioxidants both in organic solution and aqueous biphasic systems. They react by an unconventional mechanism with ROO. radicals with rate constants as high as 107 M−1 s−1 at 303 K, outperforming common phenols. The reactions proceed by oxygen atom transfer to tellurium followed by hydrogen atom transfer to the resulting RO. radical from the phenolic OH. The reaction rates do not reflect the electronic properties of the ring substituents and, because the reactions occur in a solvent cage, quenching is more efficient when the OH and TeR groups have an ortho arrangement. In the presence of thiols, hydroxyaryl alkyl tellurides act as catalytic antioxidants towards both hydroperoxides (mimicking the glutathione peroxidases) and peroxyl radicals. The high efficiency of the quenching of the peroxyl radicals and hydroperoxides could be advantageous under normal cellular conditions, but pro-oxidative (thiol depletion) when thiol concentrations are low.

  • 5. Andreoni, Alessio
    et al.
    Sen, Saptaswa
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik. Leiden Institute of Physics, Leiden University, Leiden, The Netherlands.
    Hagedoorn, Peter-Leon
    Buma, Wybren J.
    Aartsma, Thijs J.
    Canters, Gerard W.
    Fluorescence Correlation Spectroscopy of Labeled Azurin Reveals Photoinduced Electron Transfer between Label and Cu Center2018Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 24, nr 3, s. 646-654Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Fluorescent labeling of biomacromolecules enjoys increasing popularity for structural, mechanistic, and microscopic investigations. Its success hinges on the ability of the dye to alternate between bright and dark states. Forster resonance energy transfer (FRET) is an important source of fluorescence modulation. Photo-induced electron transfer (PET) may occur as well, but is often considered only when donor and acceptor are in van der Waals contact. In this study, PET is shown between a label and redox centers in oxidoreductases, which may occur over large distances. In the small blue copper protein azurin, labeled with ATTO655, PET is observed when the label is at 18.5 angstrom, but not when it is at 29.1 angstrom from the Cu. For Cu-II, PET from label to Cu occurs at a rate of (4.8 +/- 0.3) x 10(4) s(-1) and back at (0.7 +/- 0.1) x 10(3) s(-1). With Cu-I the numbers are (3.3 +/- 0.7) x 10(6) s(-1) and (1.0 +/- 0.1) x 10(4) s(-1). Reorganization energies and electronic coupling elements are in the range of 0.8-1.2 eV and 0.02-0.5 cm(-1), respectively. These data are compatible with electron transfer (ET) along a through-bond pathway although transient complex formation followed by ET cannot be ruled out. The outcome of this study is a useful guideline for experimental designs in which oxidoreductases are labelled with fluorescent dyes, with particular attention to single molecule investigations. The labelling position for FRET can be optimized to avoid reactions like PET by evaluating the structure and thermodynamics of protein and label.

  • 6.
    Bah, Juho
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Franzén, Johan
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Carbocations as Lewis Acid Catalysts in Diels-Alder and Michael Addition Reactions2014Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 20, nr 4, s. 1066-1072Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In general, Lewis acid catalysts are metal-based compounds that owe their reactivity to a low-lying empty orbital. However, one potential Lewis acid that has received negligible attention as a catalyst is the carbocation. We have demonstrated the potential of the carbocation as a highly powerful Lewis acid catalyst for organic reactions. The stable and easily available triphenylmethyl (trityl) cation was found to be a highly efficient catalyst for the Diels-Alder reaction for a range of substrates. Catalyst loadings as low as 500ppm, excellent yields, and good endo/exo selectivities were achieved. Furthermore, by changing the electronic properties of the substituents on the tritylium ion, the Lewis acidity of the catalyst could be tuned to control the outcome of the reaction. The ability of this carbocation as a Lewis acid catalyst was also further extended to the Michael reaction.

  • 7. 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.

  • 8. Chen, Lin
    et al.
    Wang, Mei
    Gloaguen, Frederic
    Zheng, Dehua
    Zhang, Peili
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Multielectron-Transfer Templates via Consecutive Two-Electron Transformations: Iron-Sulfur Complexes Relevant to Biological Enzymes2012Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 18, nr 44, s. 13968-13973Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    [FeFe] hydrogenase mimics: Two polynuclear iron-sulfur complexes (1 and 2; see figure) were prepared and structurally characterized. They are potentially effective and stable multielectron-transfer relays for mediating four- and six-electron transformations via a cascade of reversible two-electron redox steps with relatively narrow potential spans.

  • 9. Cheng, Ming
    et al.
    Yang, Xichuan
    Li, Jiajia
    Chen, Cheng
    Zhao, Jianghua
    Wang, Yu
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Dye-Sensitized Solar Cells Based on a Donor-Acceptor System with a Pyridine Cation as an Electron-Withdrawing Anchoring Group2012Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 18, nr 50, s. 16196-16202Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    New hemicyanine dyes (CM101, CM102, CM103, and CM104) in which tetrahydroquinoline derivatives are used as electron donors and N-(carboxymethyl)-pyridinium is used as an electron acceptor and anchoring group were designed and synthesized for dye-sensitized solar cells (DSSCs). Compared with corresponding dyes that have cyanoacetic acid as the acceptor, N-(carboxymethyl)-pyridinium has a stronger electron-withdrawing ability, which causes the absorption maximum of dyes to be redshifted. The photovoltaic performance of the DSSCs based on dyes CM101CM104 markedly depends on the molecular structures of the dyes in terms of the n-hexyl chains and methoxyl. The device sensitized by dye CM104 achieved the best conversion efficiency of 7.0?% (Jsc=13.4 mA?cm-2, Voc=704 mV, FF=74.8?%) under AM 1.5 irradiation (100 mW?cm-2). In contrast, the device sensitized by reference dye CMR104 with the same donor but the cyanoacetic acid as the acceptor gave an efficiency of 3.4?% (Jsc=6.2 mA?cm-2, Voc=730 mV, FF=74.8?%). Under the same conditions, the cell fabricated with N719 sensitized porous TiO2 exhibited an efficiency of 7.9?% (Jsc=15.4 mA?cm-2, Voc=723 mV, FF=72.3?%). The dyes CM101CM104 show a broader spectral response compared with the reference dyes CMR101CMR104 and have high IPCE exceeding 90?% from 450 to 580 nm. Considering the reflection of sunlight, the photoelectric conversion efficiency could be almost 100?% during this region.

  • 10. Cordova, A.
    et al.
    Sunden, H.
    Bogevig, A.
    Johansson, M.
    Himo, Fahmi
    KTH, Tidigare Institutioner, Bioteknologi.
    The direct catalytic asymmetric alpha-aminooxylation reaction: Development of stereoselective routes to 1,2-diols and 1,2-amino alcohols and density functional calculations2004Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 10, nr 15, s. 3673-3684Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    Proline-catalyzed direct asymmetric alpha-aminooxylation of ketones and aldehydes is described. The proline-catalyzed reactions between unmodified ketones or aldehydes and nitrosobenzene proceeded with excellent diastereo- and enantioselectivities. In all cases tested, the corresponding products were isolated with >95% ees. Methyl alkyl ketones were regiospecifically oxidized at the methylene carbon atom to afford enantiomerically pure alpha-aminooxylated ketones. In addition, cyclic ketones could be alpha,alpha'-dioxidized with remarkably high selectivity, furnishing the corresponding diaminooxylated ketones with >99% ees. ne reaction mechanism of the proline-catalyzed direct asymmetric alpha-aminooxylation was investigated, and we performed density functional theory (DFT) calculations in order to investigate the nature of the plausible transition states further. We also screened other organocatalysts for the asymmetric alpha-oxidation reaction and found that several proline derivatives were also able to catalyze the transformation with excellent enantioselectivities. Moreover, stereoselective routes for the synthesis of monoprotected vicinal diols and hydroxyketones were found. In addition, short routes for the direct preparation of enantiomerically pure epoxides and 1,2-amino alcohols are presented. The direct catalytic alpha-oxidation is also a novel route for the stereoselective preparation of beta-adrenoreceptor antagonists.

  • 11. 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.

  • 12.
    Dinér, Peter
    et al.
    Danish National Research Foundation, Aarhus University.
    Kjaersgaard, Anne
    Lie, Mette Alstrup
    Jørgensen, Karl Anker
    On the origin of the stereoselectivity in organocatalysed reactions with trimethylsilyl-protected Diarylprolinol2008Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 14, nr 1, s. 122-127Artikel i tidskrift (Refereegranskat)
  • 13. Dorange, Ismet
    et al.
    Löfstedt, Joakim
    Närhi, Katja
    Franzén, Johan
    Bäckvall, Jan-E
    Allenes as carbon nucleophiles in intramolecular attack on (pi-1,3-diene)palladium complexes: Evidence for trans carbopalladation of the 1,3-diene2003Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 9, nr 14, s. 3445-3449Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Reaction of allene-substituted cyclohexa- and cyclohepta-1,3-dienes with [PdCl2(PhCN)(2)] gave eta(3)-( 1,2,3)-cyclohexenyl- and eta(3)-(1,2,3)-cycloheptenylpalladium complexes. respectively. in which C-C bond formation between the allene and the 1.3-diene has occurred. Analysis of the (pi-allyl)palladium complexes by NMR spectroscopy. using reporter ligands, shows that the C-C bond formation has occurred by a trans carbopalladation involving nucleophilic attack by the middle carbon atom of the allene on a (pi-diene)palladium(n) complex. The stereochemistry of the (pi-allyl)palladium complexes was confirmed by benzoquinone-induced stereoselective transformations to allylic acetates.

  • 14. Dressel, Martina
    et al.
    Restorp, Per
    Somfai, Peter
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Total synthesis of (+)-alexine by utilizing a highly stereoselective 3+2 annulation reaction of an N-tosyl-alpha-amino aldehyde and a 1,3-bis(silyl)propene2008Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 14, nr 10, s. 3072-3077Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A novel route towards the polyhydroxylated pyrrolizidine alkaloid (+)-alexine has been developed. A key step in this synthesis is a highly stereoselective [3+2] annulation reaction of N-Ts-alpha-amino aldehyde 7a (Ts=tosyl) and 1,3-bis(silyl)propene 8a for the construction of the polyhydroxylated pyrrolidine subunit of the target molecule. Previous synthetic strategies rely on carbohydrates that require several protecting-group manipulations, thereby making the total number of steps relatively high. The [3+2] annulation strategy compares favorably with carbohydrate-based syntheses and constitutes a highly efficient entry to polyhydroxylated alkaloids.

  • 15.
    Duan, Lele
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Xu, Yunhua
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Gorlov, Mikhail
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Tong, Lianpeng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Andersson, Samir
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Chemical and Photochemical Water Oxidation Catalyzed by Mononuclear Ruthenium Complexes with a Negatively Charged Tridentate Ligand2010Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 16, nr 15, s. 4659-4668Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Two mononuclear ruthenium complexes [RuL(pic)(3)] (1) and [RuL(bpy)(pic)] (2) (H2L = 2,6-pyridinedicarboxylic acid, pic=4-picoline, bpy = 2,2'-bipyridine) have been synthesized and fully characterized. Both complexes could promote water oxidation chemically and photochemically. Compared with other known ruthenium-based water oxidation catalysts using [Ce(NH4)(2)(NO3)(6)] (Ce-IV) as the oxidant in solution at pH 1.0, complex 1 is one of the most active catalysts yet reported with an initial rate of 0.23 turnovers(-1). Under acidic conditions, the equatorial 4-picoline in complex 1 dissociates first. In addition, ligand exchange in 1 occurs when the Rum state is reached. Based on the above observations and MS measurements of the intermediates during water oxidation by 1 using Ce-IV as oxidant, [RuL(pic)(2)(H2O)](+) is proposed as the real water oxidation catalyst.

  • 16. Elie, Margaux
    et al.
    Weber, Michael D.
    Di Meo, Florent
    Sguerra, Fabien
    Lohier, Jean-Francois
    Pansu, Robert B.
    Renaud, Jean-Luc
    Hamel, Matthieu
    Linares, Mathieu
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Costa, Ruben D.
    Gaillard, Sylvain
    Role of the Bridging Group in Bis-Pyridyl Ligands: Enhancing Both the Photo- and Electroluminescent Features of Cationic (IPr) Cu-I Complexes2017Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 23, nr 64, s. 16328-16337Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report on the benefits of changing the bridging group X of bis-pyridyl ligands, that is, Py-X-Py where X is NH, CH2, C(CH3)(2), or PPh, on the photo-and electroluminescent properties of a new family of luminescent cationic H-heterocyclic carbene (NHC) copper(I) complexes. A joint experimental and theoretical study demonstrates that the bridging group affects the molecular conformation from a planar-like structure (X is NH and CH2) to a boat-like structure (X is C(CH3)(2) and PPh), leading to i) four-fold enhancement of the photoluminescence quantum yield (phi(em)) without affecting the thermally activated delayed fluorescence mechanism, and ii) one order of magnitude reduction of the ionic conductivity (sigma) of thin films. This leads to an overall enhancement of the device efficacy and luminance owing to the increased phi(em) and the use of low applied driving currents.

  • 17. Emanuelsson, Rikard
    et al.
    Löfås, Henrik
    Wallner, Andreas
    Nauroozi, Djawed
    Baumgartner, Judith
    Marschner, Christoph
    Ahuja, Rajeev
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik. Uppsala University, Sweden.
    Ott, Sascha
    Grigoriev, Anton
    Ottosson, Henrik
    Configuration- and Conformation-Dependent Electronic-Structure Variations in 1,4-Disubstituted Cyclohexanes Enabled by a Carbon-to-Silicon Exchange2014Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 20, nr 30, s. 9304-9311Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cyclohexane, with its well-defined conformers, could be an ideal force-controlled molecular switch if it were to display substantial differences in electronic and optical properties between its conformers. We utilize sigma conjugation in heavier analogues of cyclohexanes (i.e. cyclohexasilanes) and show that 1,4-disubstituted cyclohexasilanes display configuration-and conformation-dependent variations in these properties. Cis- and trans-1,4-bis(trimethylsilylethynyl)-cyclohexasilanes display a 0.11 V difference in their oxidation potentials (computed 0.11 V) and a 0.34 eV difference in their lowest UV absorption (computed difference between first excitations 0.07 eV). This is in stark contrast to differences in the corresponding properties of analogous all-carbon cyclohexanes (computed 0.02 V and 0.03 eV, respectively). Moreover, the two chair conformers of the cyclohexasilane trans isomer display large differences in electronic-structure-related properties. This enables computational design of a mechanically force-controlled conductance switch with a calculated single-molecule ON/OFF ratio of 213 at zero-bias voltage.

  • 18. Gao, Weiming
    et al.
    Sun, Junliang
    Åkermark, Torbjörn
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Li, Mingrun
    Eriksson, Lars
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Åkermark, Björn
    Attachment of a Hydrogen-Bonding Carboxylate Side Chain to an FeFe -Hydrogenase Model Complex: Influence on the Catalytic Mechanism2010Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 16, nr 8, s. 2537-2546Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Azapropanedithiolate (adt)-bridged model complexes of [FeFe]-hydrogenase bearing a carboxylic acid functionality have been designed with the aim of decreasing the potential for reduction of protons to hydrogen. Protonation of the bisphosphine complexes 4-6 has been studied by in situ IR and NMR spectroscopy, which revealed that protonation with triflic acid most likely takes place first at the N-bridge for complex 4 but at the Fe Fe bond for complexes 5 and 6. Using an excess of acid, the diprotonated species could also be observed, but none of the protonated species was sufficiently stable to be isolated in a pure state. Electrochemical studies have provided an insight into the catalytic mechanisms under strongly acidic conditions, and have also shown that complexes 3 and 6 are electro-active in aqueous solution even in the absence of acid, presumably due to hydrogen bonding. Hydrogen evolution, driven by visible light, has been observed for three-component systems consisting of [Ru(bpy)(3)](2+), complex 1, 2, or 3, and ascorbic acid in CH3CN/D2O solution by on-line mass spectrometry.

  • 19. Giussani, Angelo
    et al.
    Farahani, Pooria
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Martinez-Munoz, Daniel
    Lundberg, Marcus
    Lindh, Roland
    Roca-Sanjuan, Daniel
    Molecular Basis of the Chemiluminescence Mechanism of Luminol2019Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 25, nr 20, s. 5202-5213Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Light emission from luminol is probably one of the most popular chemiluminescence reactions due to its use in forensic science, and has recently displayed promising applications for the treatment of cancer in deep tissues. The mechanism is, however, very complex and distinct possibilities have been proposed. By efficiently combining DFT and CASPT2 methodologies, the chemiluminescence mechanism has been studied in three steps: 1)luminol oxygenation to generate the chemiluminophore, 2)a chemiexcitation step, and 3)generation of the light emitter. The findings demonstrate that the luminol double-deprotonated dianion activates molecular oxygen, diazaquinone is not formed, and the chemiluminophore is formed through the concerted addition of oxygen and concerted elimination of nitrogen. The peroxide bond, in comparison to other isoelectronic chemical functionalities (-NH-NH-, -N--N--, and -S-S-), is found to have the best chemiexcitation efficiency, which allows the oxygenation requirement to be rationalized and establishes general design principles for the chemiluminescence efficiency. Electron transfer from the aniline ring to the OO bond promotes the excitation process to create an excited state that is not the chemiluminescent species. To produce the light emitter, proton transfer between the amino and carbonyl groups must occur; this requires highly localized vibrational energy during chemiexcitation.

  • 20. Goeppert, Alain
    et al.
    Dinér, Peter
    Göteborg University.
    Ahlberg, Per
    Sommer, Jean
    Methane activation and oxidation in sulfuric acid2002Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 8, nr 14, s. 3277-3283Artikel i tidskrift (Refereegranskat)
  • 21.
    Hamberg, Anders
    et al.
    KTH, Skolan för bioteknologi (BIO), Biokemi.
    Lundgren, Stina
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Wingstrand, Erica
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Moberg, Christina
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Hult, Karl
    KTH, Skolan för bioteknologi (BIO), Biokemi.
    High Throughput Synthesis and Analysis of Acylated Cyanohydrins2007Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 13, nr 15, s. 4334-4341Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The yields and optical purities of products obtained from chiral Lewis acid/Lewis base-catalysed additions of alpha-ketonitriles to prochiral aldehydes could be accurately determined by an enzymatic method. The amount of remaining aldehyde was determined after its reduction to an alcohol, whilst the two product enantiomers were analysed after subsequent hydrolysis first by the (S)-selective Candida antarctica lipase B and then by the unselective pig liver esterase. The method could be used for analysis of products obtained from a number of aromatic aldehydes and aliphatic ketonitriles. Microreactor technology was successfully combined with high-throughput analysis for efficient catalyst optimization.

  • 22.
    Hopmann, Kathrin H.
    et al.
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Himo, Fahmi
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Theoretical study of the full reaction mechanism of human soluble epoxide hydrolase2006Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 12, nr 26, s. 6898-6909Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The complete reaction mechanism of soluble epoxide hydrolase (sEH) has been investigated by using the B3LYP density functional theory method. Epoxide hydrolases catalyze the conversion of epoxides to their corresponding vicinal diols. In our theoretical study, the sEH active site is represented by quantum-chemical models that are based on the X-ray crystal structure of human soluble epoxide hydrolase. The trans-substituted epoxide (1S,2S)-beta-methyl styrene oxide has been used as a substrate in the theoretical investigation of the sEH reaction mechanism. Both the alkylation and the hydrolytic half-reactions have been studied in detail. We present the energetics of the reaction mechanism as well as the optimized intermediates and transition-state structures. Full potential energy curves for the reactions involving nucleophilic attack at either the benzylic or the homo-benzylic carbon atom of (1S,2S)-beta-methylstyrene oxide have been computed. The regioselectivity of epoxide opening has been addressed for the two substrates (1S,2S)-beta-methylstyrene oxide and (S)-styrene oxide.

  • 23. Hou, Jungang
    et al.
    Cao, Shuyan
    Wu, Yunzhen
    Gao, Zhanming
    Liang, Fei
    Sun, Yiqing
    Lin, Zheshuai
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Inorganic Colloidal Perovskite Quantum Dots for Robust Solar CO2 Reduction2017Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 23, nr 40, s. 9481-9485Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Inorganic perovskite quantum dots as optoelectronic materials have attracted enormous attention in light-harvesting and emitting devices. However, photocatalytic conversion based on inorganic perovskite halides has not been reported. Here, we have synthesized colloidal quantum dots (QDs, 3-12 nm) of cesium lead halide perovskites (CsPbBr3) as a new type of photocatalytic material. The band gap energies and photoluminescence (PL) spectra are tunable over the visible spectral region according to quantum size effects on an atomic scale. The increased carrier lifetime revealed by time-resolved PL spectra, indicates the efficient electron-hole separation and transfer. As expected, the CsPbBr3 QDs with high selectivity of greater than 99% achieve an efficient yield of 20.9 mmolg(-1) towards solar CO2 reduction. This work has opened a new avenue for inorganic colloidal perovskite materials as efficient photocatalysts to convert CO2 into valuable fuels.

  • 24.
    Izquierdo, June
    et al.
    Univ Basque Country, Dept Quim Organ 1, UPV EHU, Manuel Lardizabal 3, San Sebastian 20018, Spain..
    Demurget, Noemie
    Univ Basque Country, Dept Quim Organ 1, UPV EHU, Manuel Lardizabal 3, San Sebastian 20018, Spain..
    Landa, Aitor
    Univ Basque Country, Dept Quim Organ 1, UPV EHU, Manuel Lardizabal 3, San Sebastian 20018, Spain..
    Brinck, Tore
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Tillämpad fysikalisk kemi.
    Mercero, Jose M.
    Euskal Herriko Unibertsitatea, Kimika Fak, UPV EHU, Donostia San Sebastian, Spain.;Donostia Int Phys Ctr DIPC, Donostia San Sebastian, Spain..
    Dinér, Peter
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Organisk kemi.
    Oiarbide, Mikel
    Univ Basque Country, Dept Quim Organ 1, UPV EHU, Manuel Lardizabal 3, San Sebastian 20018, Spain..
    Palomo, Claudio
    Univ Basque Country, Dept Quim Organ 1, UPV EHU, Manuel Lardizabal 3, San Sebastian 20018, Spain..
    Asymmetric Synthesis of Adjacent Tri- and Tetrasubstituted Carbon Stereocenters: Organocatalytic Aldol Reaction of an Hydantoin Surrogate with Azaarene 2-Carbaldehydes2019Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A bifunctional amine/squaramide catalyst promoted direct aldol addition of an hydantoin surrogate to pyridine 2-carbaldehyde N-oxides to afford adducts bearing two vicinal tertiary/quaternary carbons in high diastereo- and enantioselectivity (d.r. up to >20:1; ee up to 98 %) is reported. Acid hydrolysis of adducts followed by reduction of the N-oxide group yields enantiopure carbinol-tethered quaternary hydantoin-azaarene conjugates with densely functionalized skeletons. DFT studies of the potential energy surface (B3LYP/6-31+G(d)+CPCM (dichloromethane)) of the reaction correlate the activity of different catalysts and support an intramolecular hydrogen-bond-assisted activation of the squaramide moiety in the transition state of the catalytic reaction.

  • 25. Jalilehvand, F.
    et al.
    Eriksson, L.
    Glaser, Julius
    KTH, Tidigare Institutioner                               , Kemi.
    Maliarik, M.
    Mink, J.
    Sandstrom, M.
    Toth, I.
    Toth, J.
    Tl-Pt(CN)(5) in the solid state - A multimethod study of an unusual compound containing inorganic wires2001Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 7, nr 10, s. 2167-2177Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The crystal and molecular structure of a polycrystalline powder with a metal-metal bond and the composition TlPt(CN)(5) has been determined by combining results from X-ray powder diffraction (XRD), extended X-ray absorption fine structure (EXAFS) and vibrational spectroscopic studies. The XRD data gave the tetragonal space group P4/nmm (No. 129). with a = 7.647(3), c = 8.049(3) Angstrom, Z = 2, and well-determined positions of the heavy metal atoms. The Pt-Tl bond length in the compound is 2.627(2) Angstrom. The platinum atom coordinates four equivalent equatorial cyano ligands, with a fifth axial CN ligand and a thallium atom completing a distorted octahedral coordination geometry. The Tl-Pt(CN)(5) entities are linked together in linear -NC-Pt-Tl-NC-Pt-Tl chains through the axial cyano ligand. These linear wires are the essential structural features and influence the properties of the com-pound. A three-dimensional network is formed by the four equatorial cyano ligands of the platinum atom that form bridges to the thallium atoms of neighbouring antiparallel chains. The platinum atom and the five nitrogen atoms from the bridging cyano groups form a distorted octahedron around the thallium atom. EXAFS data were recorded at the Pt and Tl L-III edges for a more complete description of the local structure around the Pt and Tl atoms. The excessive multiple scattering was evaluated by means of the FEFF program. Raman and infrared absorption spectroscopy reveal strong coupling of the vibrational modes of the TlPt(CN)(5) entities, in particular the metal - metal stretching mode, which is split into four Raman and two IR bands. Factor group theory shows that a structural unit larger than the crystallographic unit cell must be used to assign vibrational bands. Intra- and intermolecular force constants have also been calculated. The compound exhibits red luminescence at 700+/- 3 nm in glycerol and has a corresponding excitation maximum at 240 nm. X-ray photoelectron spectra (XPS) show that the metal atoms have intermediate oxidation states, Pt3.2+ and Tl1.6+, between those in the parent Pt-II and Tl-III species and the decomposition products, Pt-IV and Tl-I. The solid compound TlPt(CN)(5) is stable to 520 degreesC. However in presence of water, a two-electron transfer between the metal atoms results in the cleavage of the metal-metal bond at 80 degreesC, forming a Pt-IV pentacyanohydrate complex and a monovalent thallium ion.

  • 26.
    Johansson, Adam Johannes
    et al.
    Rhein Westfal TH Aachen, Inst Organ Chem.
    Zuidema, Erik
    Bolm, Carsten
    On the Mechanism of Ruthenium-Catalyzed Formation of Hydrogen from Alcohols: A DFT Study2010Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 16, nr 45, s. 13487-13499Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The mechanism of the ruthenium-catalyzed dehydrogenation of methanol has been investigated by using three DFT-based methods. Three pathways were considered in which the ruthenium catalyst was ligated by either two or three phosphine ligands. Dispersion interactions, which are not described by the popular B3LYP functional, were taken into account by using the dispersion-corrected B3LYP-D and M06 density functionals. These interactions were found to be important in the description of reaction steps that involved ligand/substrate/product association with or dissociation from the catalyst. In line with experimental results, the resting state of the catalyst was predicted to be a ruthenium trihydride complex. It is shown that the dehydrogenation reaction preferentially proceeds through pathways in which the catalyst is ligated by two phosphine ligands. The catalytic cycle of the dehydrogenation process involves an inter-molecular proton transfer from the methanol substrate to the catalyst followed by the release of dihydrogen. Rate-determining beta-hydride elimination from the resulting methoxide species then regenerates the resting state of the catalyst and completes the catalytic cycle. The overall free-energy barriers of 29.6-31.4 kcal mol(-1) predicted by the three density functionals are in good agreement with the experimentally observed reaction rate of 6 h(-1) at 423 K.

  • 27. Karkas, Markus D.
    et al.
    Johnston, Eric V.
    Karlsson, Erik A.
    Lee, Bao-Lin
    Åkermark, Torbjörn
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Shariatgorji, Mohammadreza
    Ilag, Leopold
    Hansson, Örjan
    Bäckvall, Jan-E.
    Åkermark, Björn
    Light-Induced Water Oxidation by a Ru complex Containing a Bio-Inspired Ligand2011Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 17, nr 28, s. 7953-7959Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The new Ru complex 8 containing the bio-inspired ligand 7 was successfully synthesized and characterized. Complex 8 efficiently catalyzes water oxidation using Ce(IV) and Ru(III) as chemical oxidants. More importantly, this complex has a sufficiently low overpotential to utilize ruthenium polypyridyl-type complexes as photosensitizers.

  • 28.
    Karlsson, Karl Martin
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi. KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    Jiang, Xiao
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi. KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    Eriksson, Susanna K
    Gabrielsson, Erik
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi. KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    Rensmo, Håkan
    Hagfeldt, Anders
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi. KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    Phenoxazine Dyes for Dye-Sensitized Solar Cells: Relationship Between Molecular Structure and Electron Lifetime.2011Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 17, nr 23, s. 6415-6424Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A series of metal-free organic dyes with a core phenoxazine chromophore have been synthesized and tested as sensitizers in dye-sensitized solar cells. Overall conversion efficiencies of 6.03-7.40 % were reached under standard AM 1.5G illumination at a light intensity of 100 mW cm(-2) . A clear trend in electron lifetime could be seen; a dye with a furan-conjugated linker showed a shorter lifetime relative to dyes with the acceptor group directly attached to the phenoxazine. The addition of an extra donor unit, which bore insulating alkoxyl chains, in the 7-position of the phenoxazine could increase the lifetime even further and, together with additives in the electrolyte to raise the conduction band, an open circuit voltage of 800 mV could be achieved. From photoelectron spectroscopy and X-ray absorption spectroscopy of the dyes adsorbed on TiO(2) particles, it can be concluded that the excitation is mainly of cyano character (i.e., on average, the dye molecules are standing on, and pointing out, from the surface of TiO(2) particles).

  • 29. Kuznetsov, Alexei N.
    et al.
    Kloo, Lars
    KTH, Tidigare Institutioner                               , Kemi.
    Lindsjö, Martin
    KTH, Tidigare Institutioner                               , Kemi.
    Rosdahl, Jan
    KTH, Tidigare Institutioner                               , Kemi.
    Stoll, Hermann
    Ab initio Calculations on Bismuth Cluster Polycations2001Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 7, nr 13, s. 2821-2828Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ab initio calculations on bismuth polycationic species of the types Bi-n((n-2)+), Bi-n((n-4)+), and Bi-n((n-6)+) (n = 3 -12) were performed at the Hartree -Fock and density functional theory levels in order to investigate their general properties and the applicability of Wade's rules on bismuth polycations. Some exceptions to Wade's rules were encountered, and, moreover, several predicted and calculated minima shaw only meta-stable behavior. The bonding in bismuth polycations is characterized by a high degree of electron delocalization and "three-dimensional aromaticity".

  • 30.
    Laurell Nash, Anna
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Hertzberg, Robin
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Wen, Ye-Qian
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Dahlgren, Björn
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Brinck, Tore
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Moberg, Christina
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Dual Lewis Acid/Lewis Base Catalyzed Acylcyanation of Aldehydes: A Mechanistic Study2016Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 22, nr 11, s. 3821-3829Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A mechanistic investigation, which included a Hammett correlation analysis, evaluation of the effect of variation of catalyst composition, and low-temperature NMR spectroscopy studies, of the Lewis acid-Lewis base catalyzed addition of acetyl cyanide to prochiral aldehydes provides support for a reaction route that involves Lewis base activation of the acyl cyanide with formation of a potent acylating agent and cyanide ion. The cyanide ion adds to the carbonyl group of the Lewis acid activated aldehyde. O-Acylation by the acylated Lewis base to form the final cyanohydrin ester occurs prior to decomplexation from titanium. For less reactive aldehydes, the addition of cyanide is the rate-determining step, whereas, for more reactive, electron-deficient aldehydes, cyanide addition is rapid and reversible and is followed by rate-limiting acylation. The resting state of the catalyst lies outside the catalytic cycle and is believed to be a monomeric titanium complex with two alcoholate ligands, which only slowly converts into the product.

  • 31.
    Liao, Rong-Zhen
    et al.
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Yu, Jian-Guo
    Raushel, Frank M.
    Himo, Fahmi
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Theoretical investigation of the reaction mechanism of the dinuclear zinc enzyme dihydroorotase2008Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 14, nr 14, s. 4287-4292Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The reaction mechanism of the dinuclear zinc enzyme dihydroorotase was investigated by using hybrid density functional theory. This enzyme catalyzes the reversible interconversion of dihydroorotate and carbamoyl aspartate. Two reaction mechanisms in which the important active site residue Asp250 was either protonated or unprotonated were considered. The calculations establish that Asp250 must be unprotonated for the reaction to take place. The bridging hydroxide is shown to be capable of performing nucleophilic attack on the substrate from its bridging position and the role of Znβ is argued to be the stabilization of the tetrahedral intermediate and the transition state leading to it, thereby lowering the barrier for the nucleophilic attack. It is furthermore concluded that the rate-limiting step is the protonation of the amide nitrogen by Asp250 coupled with C-N bond cleavage, which is consistent with previous experimental findings from isotope labeling studies.

  • 32. Lin, Shuangzheng
    et al.
    Zhao, Gui-Ling
    Deiana, Luca
    Sun, Junliang
    Zhang, Qiong
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Leijonmarck, Hans
    Cordova, Armando
    Dynamic Kinetic Asymmetric Domino Oxa-Michael/Carbocyclization by Combination of Transition-Metal and Amine Catalysis: Catalytic Enantioselective Synthesis of Dihydrofurans2010Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 16, nr 47, s. 13930-13934Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A one-pot highly chemo- and enantioselective catalytic domino oxa-Michael/carbocyclization between α,β-unsaturated aldehydes and propargylic alcohols is presented. This dynamic kinetic transformation requires a combination of transition-metal and amine catalysis to afford functionalized dihydrofurans in good to high yields and up to 99.5:0.5 e.r.

  • 33. Lindström, U. M.
    et al.
    Somfai, Peter
    KTH, Tidigare Institutioner                               , Kemi.
    Aza- 3,3 -claisen enolate rearrangement in vinylaziridines: Stereoselective synthesis of mono-, di-, and trisubstituted seven-membered lactams2001Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 7, nr 1, s. 94-98Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Several 2,3-disubstituted vinylaziridines have been N-acylated and subjected to LiHMDS in THF at - 78 degreesC. Upon warming to room temperature, the resulting amide enolates underwent a highly stereoselective [3,3]-sigmatropic rearrangement to give mono-, di-, and trisubstituted seven-membered lactams in good yields. The scope and limitations of the process have been investigated by using variously substituted vinylaziridines. A kinetically controlled process proceeding through a six-membered boatlike transition state assembly has been invoked to explain the stereochemical outcome of the reaction.

  • 34. Liu, T. B.
    et al.
    Wang, M.
    Shi, Z.
    Cui, H. G.
    Dong, W. B.
    Chen, J. S.
    Akermark, B.
    Sun, Licheng C.
    Synthesis, structures and electrochemical properties of nitro- and amino-functionalized diiron azadithiolates as active site models of Fe-only hydrogenases2004Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 10, nr 18, s. 4474-4479Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Complex [{(mu-SCH2)(2)N(4-NO2C6H4)}Fe-2(CO)(6)] (4) was prepared by the reaction of the dianionic intermediate [(mu-S)(2)Fe-2(CO)(6)](2-) and N,N-bis(chloromethyl)-4-nitroaniline as a biomimetic model of the active site of Fe-only hydrogenase. The reduction of 4 by Pd-C/H-2 under a neutral condition afforded complex [{(mu-SCH2)(2)N(4-NH2C6H4)}Fe-2(CO)(6)] (5) in 67% yield. Both complexes were characterized by IR, H-1 and C-13 NMR spectroscopy and MS spectrometry. The molecular structure of 4, as determined by X-ray analysis, has a butterfly 2Fe2S core and the aryl group on the bridged-N atom slants to the Fe(2) site. Cyclic voltammograms of 4 and 5 were studied to evaluate their redox properties. It was found that complex 4 catalyzed electrochemical proton reduction in the presence of acetic acid. A plausible mechanism of the electrocatalytic proton reduction is discussed.

  • 35.
    Marcelli, Tommaso
    et al.
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Hammar, Peter
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Himo, Fahmi
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Phosphoric Acid Catalyzed Enantioselective Transfer Hydrogenationof Imines: A Density Functional Theory Study of Reaction Mechanismand the Origins of Enantioselectivity2008Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 14, s. 8562-8571Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The phosphoric acid catalyzedreaction of 1,4-dihydropyridineswith N-arylimines has been investigatedby using density functional theory.We first considered the reaction of acetophenonePMP-imine (PMP=p-methoxyphenyl)with the dimethylHantzsch ester catalyzed by diphenylphosphate. Our study showed that, inagreement with what has previouslybeen postulated for other reactions, diphenylphosphate acts as a Lewis base/Brønsted acid bifunctional catalyst inthis transformation, simultaneously activatingboth reaction partners. The calculationsalso showed that the hydridetransfer transition states for the E andZ isomers of the iminium ion havecomparable energies. This observationturned out to be crucial to the understandingof the enantioselectivity of theprocess. Our results indicate that whenusing a chiral 3,3’-disubstituted biarylphosphoric acid, hydride transfer to theRe face of the (Z)-iminium is energeticallymore favorable and is responsiblefor the enantioselectivity, whereas thecorresponding transition states for nucleophilicattack on the two faces ofthe (E)-iminium are virtually degenerate.Moreover, model calculations predictthe reversal in enantioselectivityobserved in the hydrogenation of 2-arylquinolines,which during the catalyticcycle are converted into (E)-iminiumions that lack the flexibility of thosederived from acyclic N-arylimines. Inthis respect, the conformational rigidityof the dihydroquinolinium cation imposesan unfavorable binding geometryon the transition state for hydridetransfer on the Re face and is thereforeresponsible for the high enantioselectivity.

  • 36.
    Marcos, Rocio
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Bertini, Federica
    CNR, Inst Chim Composti Organometallici ICCOM, Via Madonna Piano 10, I-50019 Florence, Italy..
    Rinkevicius, Zilvinas
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Peruzzini, Maurizio
    CNR, Inst Chim Composti Organometallici ICCOM, Via Madonna Piano 10, I-50019 Florence, Italy..
    Gonsalvi, Luca
    CNR, Inst Chim Composti Organometallici ICCOM, Via Madonna Piano 10, I-50019 Florence, Italy..
    Ahlquist, Mårten S. G.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Mechanistic Studies on NaHCO3 Hydrogenation and HCOOH Dehydrogenation Reactions Catalysed by a Fe-II Linear Tetraphosphine Complex2018Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 24, nr 20, s. 5366-5372Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present a theoretical extension of the previously published bicarbonate hydrogenation to formate and formic acid dehydrogenation catalysed by Fe-II complexes bearing the linear tetraphosphine ligand tetraphos-1. The hydrogenation reaction was found to proceed at the singlet surface with two competing pathways: A)H-2 association to the Fe-H species followed by deprotonation to give a Fe(H)(2) intermediate, which then reacts with CO2 to give formate. B)CO2 insertion into the Fe-H bond, followed by H-2 association and subsequent deprotonation. B was found to be slightly preferred with an activation energy of 22.8kcalmol(-1), compared to 25.3 for A. Further we have reassigned the Fe-H complex, as a Fe(H)(H-2), which undergoes extremely rapid hydrogen exchange.

  • 37.
    Merenyi, Gabor
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    Lind, Johan
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    Naumov, Sergej
    von Sonntag, Clemens
    The Reaction of Ozone with the Hydroxide Ion: Mechanistic Considerations Based on Thermokinetic and Quantum Chemical Calculations and the Role of HO4- in Superoxide Dismutation2010Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 16, nr 4, s. 1372-1377Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The reaction of OH- with O-3 eventually leads to the formation of center dot OH radicals. In the original mechanistic concept (J. Staehelin, J. Hoigne, Environ. Sci. Technol. 1982, 16, 676-681) it was suggested that the first step occurred by O transfer: OH- + O-3 -> HO2- + O-2 and that center dot OH was generated in the subsequent reaction(s) of HO2- with O-3 (the peroxone process). This mechanistic concept has now been revised on the basis of thermokinetic and quantum chemical calculations. A onestep O transfer such as that mentioned above would require the release of O-2 in its excited singlet state (O-1(2), O-2-((1)Delta(g))); this state lies 95.5 kJ mol(-1) above the triplet ground state ((3)Sigma(-)(g))). The low experimental rate constant of 70m(-1) s(-1) is not incompatible with such a reaction. However, according to our calculations, the reaction of OH- with O-3 to form an adduct (OH- + O-3 -> HO4-; Delta G = 3.5 kJ mol(-1)) is a much better candidate for the rate-determining step as compared with the significantiv more endergonic O transfer (Delta G=26.7 kJ mol(-1)). Hence, we favor this reaction; all the more so as numerous precedents of similar ozone adduct formation are known in the literature. Three potential decay routes of the adduct HO4- have been probed: HO4- -> HO2- + O-1(2) is spin allowed, but markedly endergonic (Delta G=23.2 kJ mol(-1)). HO4- -> HO2- + O-3(2) is spin forbidden (Delta G = -73.3 kJ mol(-1)). The decay into radicals, HO4- -> HO2 center dot + O-2(center dot-), is spin allowed and less endergonic (Delta G=14.8 kJ mol(-1)) than HO4- -> HO2- + O-1(2). It is thus HO4- -> HO2 center dot + O-2(center dot-) by which HO4- decays. It is noted that a large contribution of the reverse of this reaction, HO2 center dot + O-2(center dot-)-> HO4-, followed by HO4- -> HO2- + O-3(2), now explains why the measured rate of the bimolecular decay of HO2 center dot and O-2(center dot-) into HO2- + O-2 (k=1x10(8) m(-1) s(-1)) is below diffusion controlled. Because k for the process HO4- -> HO2 center dot + O-2(center dot-) is much larger than k for the reverse of OH- + O-3 -> HO4-, the forward reaction OH- + O-3 -> HO4- is practically irreversible.

  • 38.
    Mesas-Sanchez, Laura
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Dinér, Peter
    KTH, Skolan för kemivetenskap (CHE), Kemi. Uppsala University, Sweden.
    A Mechanistic Investigation of the Kinetic Resolution of Secondary Aromatic Alcohols Using a Ferrocene-Based Planar Chiral 4-(Dimethylamino)pyridine Catalyst2015Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 21, nr 14, s. 5623-5631Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A detailed computational and kinetic analysis of the acetylation of 1-phenylethanol with acetic anhydride catalyzed by planar chiral 4-(dimethylamino) pyridine (DMAP) catalyst ( )-1 is presented. The study includes a computational investigation of the potential-energy surface including the acylation and stereoselective transition states at the DFT level of theory. Experimentally, the kinetic study shows that the reaction proceeds in a first-order manner in catalyst, whereas both substrates, acetic anhydride and 1-phenylethanol, show fractional order, which is in accordance with steady-state conditions. The fractional order depends on an equilibrium between the free catalyst and the acetylated catalyst.

  • 39.
    Natarajan Arul, Murugan
    et al.
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Aidas, Kestutis
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Kongsted, Jacob
    Rinkevicius, Zilvinas
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Ågren, Hans
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    NMR Spin-Spin Coupling Constants in Polymethine Dyes as Polarity Indicators2012Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 18, nr 37, s. 11677-11684Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Herein, we explore the use of spinspin coupling constants (SSCCs) in merocyanine (MCYNE) dyes as indicators of polarity. For this purpose, we use CarParrinello hybrid quantum mechanics/molecular mechanics (QM/MM) to determine the structures of MCYNE in solvents of different polarity, followed by computations of the SSCCs by using QM/MM linear-response theory. The molecular geometry of MCYNE switches between neutral, cyanine-like, and zwitterionic depending on the polarity of the solvent. This structural variation is clearly reflected in the proton SSCCs in the polymethine backbone, which are highly sensitive to the dielectric nature of the environment; this mechanism can be used as a polarity indicator for different microenvironments. This result is highlighted by computing the SSCCs of the MCYNE probe in the cavity of the beta-lactoglobulin protein. The computed SSCCs clearly indicate a non-polar hydrophobic dielectric nature of this cavity.

  • 40.
    Ning, Zhijun
    et al.
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Tian, Haining
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Yuan, Chunze
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Fu, Ying
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Ågren, Hans
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Pure Organic Redox Couple for Quantum-Dot-Sensitized Solar Cells2011Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 17, nr 23, s. 6330-6333Artikel i tidskrift (Refereegranskat)
  • 41.
    Närhi, Katja
    et al.
    Stockholm University.
    Franzén, Johan
    Stockholm University.
    Bäckvall, Jan Erling
    Stockholm University.
    Palladium(0)-catalyzed cycloisomerization of enallenes2005Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 11, nr 23, s. 6937-6943Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A novel palladium(0)-catalyzed cycloisomerization of enallenes has been developed. This reaction, catalyzed by [Pd(dba)(2)] (dba=dibenzylideneacetone) in acetic acid, results in the formation of cyclopentene derivatives and [n.3.0]bicyclic systems (n=3, 4) in good to high yields. The carbon-carbon bond-forming step is highly stereoselective to give cis-fused bicyclic systems. The presence of acetic acid as solvent and dba as ligand for palladium(0) turned out to be essential for the reaction in order to provide good reactivity and regioselectivity.

  • 42. Odille, Fabrice G. J.
    et al.
    Jonsson, Stefan
    Stjernqvist, Susann
    Rydén, Tobias
    Lund University.
    Wärnmark, Kenneth
    On the Characterization of Dynamic Supramolecular Systems: A General Mathematical Association Model for Linear Supramolecular Copolymers and Application on a Complex Two-Component Hydrogen-Bonding System2007Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 13, nr 34, s. 9617-9636Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A general mathematical model for the characterization of the dynamic (kinetically labile) association of supramolecular assemblies in solution is presented. It is an extension of the equal K (EK) model by the stringent use of linear algebra to allow for the simultaneous presence of an unlimited number of different units in the resulting assemblies. It allows for the analysis of highly complex dynamic equilibrium systems in solution, including both supramolecular homo- and copolymers without the recourse to extensive approximations, in a field in which other analytical methods are difficult. The derived mathematical methodology makes it possible to analyze dynamic systems such as supramolecular copolymers regarding for instance the degree of polymerization, the distribution of a given monomer in different copolymers as well as its position in an aggregate. It is to date the only general means to characterize weak supramolecular systems. The model was fitted to NMR dilution titration data by using the program Matlab((R)), and a detailed algorithm for the optimization of the different parameters has been developed. The methodology is applied to a case study, a hydrogen-bonded supramolecular system, salen 4+porphyrin 5. The system is formally a two-component system but in reality a three-component system. This results in a complex dynamic system in which all monomers are associated to each other by hydrogen bonding with different association constants, resulting in homo- and copolymers 4,,5,, as well as cyclic structures 6 and 7, in addition to free 4 and 5. The system was analyzed by extensive NMR dilution titrations at variable temperatures. All chemical shifts observed at different temperatures were used in the fitting to obtain the Delta H degrees and Delta S degrees values producing the best global fit. From the derived general mathematical expressions, system 4+5 could be characterized with respect to above-mentioned parameters.

  • 43. Olenev, Andrei
    et al.
    Oleneva, Olga
    Lindsjö, Martin
    KTH, Tidigare Institutioner                               , Kemi.
    Kloo, Lars
    KTH, Tidigare Institutioner                               , Kemi.
    Shevelkov, Andrei
    Coordinated and clathrated guests in the (3)(infinity)[Hg6As4](4+) bicompartmental framework: Synthesis, crystal and electronic structure, and properties of the novel supramolecular complexes [Hg6As4](CrBr6)Br and [Hg6As4](FeBr6)Hg-0.62003Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 9, nr 14, s. 3201-3208Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Two new supramolecular complexes [Hg6As4](CrBr6)Br (1) and [Hg6As4](FeBr6)Hg-0.6 (2) have been prepared by the standard ampoule technique and their crystal structures determined. Both crystallize in the cubic space group PO with the unit cell parameter a = 12.275(1) (1) and 12.332(1) Angstrom (2), and Z = 4. Their structures consist of bicompartmental, three-dimensional [Hg6As4](4+) frameworks with cavities of two different sizes occupied by guest anions of different type. ne bigger cavities are filled with the octahedral MBr6n- ions (M = Cr or Fe; n = 3 or 4), whereas the smaller cavities trap either Br- ions (1) or Hg-0 (2). The analysis of the host-guest contacts has allowed a classification of the octahedral guests as coordinated and the monatomic guests as clathrated. Magnetic measurements and ESR spectroscopy data have given information about the interaction between the host and guests. Band structure calculations (HF and hybrid DFT level) indicate that both 1 and 2 are non-metallic, with a band gap of approximately 1.5 eV (B3LYP), and that the interaction between the host and guests is of predominantly electrostatic character. It is shown that though the electrostatic host-guest interaction is weak it plays an important role in assembling the perfectly ordered supramolecular architectures.

  • 44. Polukeev, Alexey V.
    et al.
    Marcos, Rocio
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Ahlquist, Mårten S. G.
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Wendt, Ola F.
    Solvent-Dependent Structure of Iridium Dihydride Complexes: Different Geometries at Low and High Dielectricity of the Medium2016Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 22, nr 12, s. 4078-4086Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The hydride iridium pincer complex [(PCyP)IrH2] (PCyP=cis-1,3-bis[(di-tert-butylphosphino)methyl]cyclohexane, 1) reveals remarkably solvent-dependent hydride chemical shifts, isotope chemical shifts, J(HD) and T-1(min), with r(HH) increasing upon moving to more polar medium. The only known example of such behaviour (complex [(POCOP)IrH2], POCOP=2,6-(tBu(2)PO)(2)C6H3) was explained by the coordination of a polar solvent molecule to the iridium (J. Am. Chem. Soc. 2006, 128, 17114). Based on the existence of an agostic bond between -C-H and iridium in 1 in all solvents, we argue that the coordination of solvent can be rejected. DFT calculations revealed that the structures of 1 and [(POCOP)IrH2] depend on the dielectric permittivity of the medium and these compounds adopt trigonal-bipyramidal geometries in non-polar media and square-pyramidal geometries in polar media.

  • 45. Privalov, Timofei
    et al.
    Åkermark, Björn
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    The O-O Bonding in Water Oxidation: the Electronic Structure Portrayal of a Concerted Oxygen Atom-Proton Transfer Pathway2011Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 17, nr 30, s. 8313-8317Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The two-phased reaction: Calculations on the monomeric ruthenium catalyst with 1,10-phenanthroline-2,9-dicarboxylic acid reveals an interaction of the RuV=O complex with water that proceeds through two main phases and involves partial charge separation in an early encounter complex. Further along the reaction path, that effect leads to an electronic reorganization in the Ru complex; this directs the donor-acceptor interaction between the attacking water and the COO-group in concert with the O-atom transfer to form an O-O bond via a relatively low-energy barrier (see graphic).

  • 46.
    Rahm, Martin
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Fysikalisk kemi.
    Brinck, Tore
    KTH, Skolan för kemivetenskap (CHE), Kemi, Fysikalisk kemi.
    Kinetic Stability and Propellant Performance of Green Energetic Materials2010Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 16, s. 6590-6600Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A thorough theoretical investigation of four promising green energetic materials is presented. The kinetic stability of the dinitramide, trinitrogen dioxide, pentazole, and oxopentazole anions has been evaluated in the gas phase and in solution by using high-level ab initio and DFT calculations. Theoretical UV spectra, solid-state heats of formation, density, as well as propellant performance for the corresponding ammonium salts are reported. All calculated properties for dinitramide are in excellent agreement with experimental data. The stability of the trinitrogen dioxide anion is deemed sufficient to enable synthesis at low temperature, with a barrier for decomposition of approximately 27.5 kcal mol(-1) in solution. Oxopentazolate is expected to be approximately 1200 times more stable than pentazolate in solution, with a barrier exceeding 30 kcal mol(-1), which should enable handling at room temperature. All compounds are predicted to provide high specific impulses when combined with aluminum fuel and a polymeric binder, and rival or surpass the performance of a corresponding ammonium perchlorate based propellant. The investigated substances are also excellent monopropellant candidates. Further study and attempted synthesis of these materials is merited.

  • 47.
    Ramström, Olof
    et al.
    KTH, Tidigare Institutioner, Kemi.
    Lohmann, S.
    Bunyapaiboonsri, T.
    Lehn, J. M.
    Dynamic combinatorial carbohydrate libraries: Probing the binding site of the concanavalin A lectin2004Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 10, nr 7, s. 1711-1715Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Dynamic combinatorial chemistry (DCC) has emerged as an efficient approach to receptor/ligand identification based on the generation of combinatorial libraries by reversible interconversion of the library constituents. In this study, the implementation of such libraries on carbohydrate-lectin interactions was examined with the plant lectin Concanavalin A as a target species. Dynamic carbohydrate libraries were generated from a pool of carbohydrate aldehydes and hydrazide linker/scaffold components through re- versible acylhydrazone exchange, resulting in libraries containing up to 474 constituents. Dynamic deconvolution allowed the efficient identification of the structural features required for binding to Concanavalin A and the selection of a strong binder, a tritopic mannoside, showing an IC50-value of 22 mum.

  • 48. Ren, Bo
    et al.
    Ramström, Olof
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Zhang, Qiang
    Ge, Jiantao
    Dong, Hai
    An Iron(III) Catalyst with Unusually Broad Substrate Scope in Regioselective Alkylation of Diols and Polyols2016Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 22, nr 7, s. 2481-2486Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study, [Fe(dibm)(3)] (dibm=diisobutyrylmethane) is shown to have unusually broad scope as a catalyst for the selective monoalkylation of a diverse set of 1,2- and 1,3-diol-containing structures. The mechanism is proposed to proceed via a cyclic dioxolane-type intermediate, formed between the iron(III) species and two adjacent hydroxyl groups. This approach represents the first transition-metal catalysts that are able to replace stoichiometric amounts of organotin reagents in regioselective alkylation. The reactions generally lead to very high regioselectivities and high yields, on par with, or better than, previous methods used for regioselective alkylation.

  • 49.
    Rubio-Magnieto, Jenifer
    et al.
    Univ Mons UMONS, Ctr Innovat Mat & Polymers, Lab Chem Novel Mat, 20 Pl Parc, B-7000 Mons, Belgium.;Univ Jaume 1, Dept Quim Inorgan & Organ, Bioinspired Supramol Chem & Mat Grp, Avda Sos Baynat S-N, E-12071 Castellon de La Plana, Spain..
    Kajouj, Sofia
    Univ Libre Bruxelles, Chim Organ & Photochim CP160 08, 50 Ave FD Roosevelt, B-1050 Brussels, Belgium..
    Di Meo, Florent
    Univ Limoges, Sch Pharm, INSERM, U1248,IPPRITT, 2 Rue Dr Marcland, F-87025 Limoges, France..
    Fossepre, Mathieu
    Univ Mons UMONS, Ctr Innovat Mat & Polymers, Lab Chem Novel Mat, 20 Pl Parc, B-7000 Mons, Belgium..
    Trouillas, Patrick
    Univ Limoges, Sch Pharm, INSERM, U1248,IPPRITT, 2 Rue Dr Marcland, F-87025 Limoges, France.;Palacky Univ, Fac Sci, RCPTM, Slechtitelu 27, Olomouc 78371, Czech Republic..
    Norman, Patrick
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Linares, Mathieu
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi. KTH, Centra, SeRC - Swedish e-Science Research Centre.
    Moucheron, Cecile
    Univ Libre Bruxelles, Chim Organ & Photochim CP160 08, 50 Ave FD Roosevelt, B-1050 Brussels, Belgium..
    Surin, Mathieu
    Univ Mons UMONS, Ctr Innovat Mat & Polymers, Lab Chem Novel Mat, 20 Pl Parc, B-7000 Mons, Belgium..
    Binding Modes and Selectivity of Ruthenium Complexes to Human Telomeric DNA G-Quadruplexes2018Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 24, nr 58, s. 15577-15588Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Metal complexes constitute an important class of DNA binders. In particular, a few ruthenium polyazaaromatic complexes are attractive as light switches because of their strong luminescence enhancement upon DNA binding. In this paper, a comprehensive study on the binding modes of several mononuclear and binuclear ruthenium complexes to human telomeric sequences, made of repeats of the d(TTAGGG) fragment is reported. These DNA sequences form G-quadruplexes (G4s) at the ends of chromosomes and constitute a relevant biomolecular target in cancer research. By combining spectroscopy experiments and molecular modelling simulations, several key properties are deciphered: the binding modes, the stabilization of G4 upon binding, and the selectivity of these complexes towards G4 versus double-stranded DNA. These results are rationalized by assessing the possible deformation of G4 and the binding free energies of several binding modes via modelling approaches. Altogether, this comparative study provides fundamental insights into the molecular recognition properties and selectivity of Ru complexes towards this important class of DNA G4s.

  • 50.
    Sakulsombat, Morakot
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Vongvilai, Pornrapee
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Ramström, Olof
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Efficient Asymmetric Synthesis of 1-Cyano-tetrahydroisoquinolines from Lipase Dual Activity and Opposite Enantioselectivities in alpha-Aminonitrile Resolution2014Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 20, nr 36, s. 11322-11325Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Dual promiscuous racemization/amidation activities of lipases leading to efficient dynamic kinetic resolution protocols of racemic alpha-aminonitrile compounds are described. alpha-Amidonitrile products of high enantiomeric purity could be formed in high yields. Several lipases from different sources were shown to exhibit the dual catalytic activities, where opposite enantioselectivities could be recorded for certain substrates.

12 1 - 50 av 82
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • harvard1
  • 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