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  • 1. Baryshnikov, G. V.
    et al.
    Minaev, Boris F.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Minaeva, V. A.
    Ning, Zhijun
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Zhang, Qiong
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Structure and Spectral Properties of Truxene Dye S52012In: Optics and Spectroscopy, ISSN 0030-400X, E-ISSN 1562-6911, Vol. 112, no 2, p. 168-174Article in journal (Refereed)
    Abstract [en]

    On the ground of functional theory with the B3LYP and BMK functionals, we have studied the structure and optical properties of a truxene dye sensitizer S5 for photoelectric transducers. Based on the calculations of the vertical excitations energy of the dye molecule and accounting the influence of the solvent, we have revealed a positive solvatochromic effect that is weak compared to results obtained in the vacuum approximation. We have studied new features describing stabilization of the planar structure of the cyanothiophene-acrylic fragment of the S5 dye.

  • 2.
    Baryshnikov, Gleb
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. Bohdan Khmelnytsky National University, Ukraine.
    Minaev, Boris
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. Bohdan Khmelnytsky National University, Ukraine.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. Siberian Federal University, Russia.
    Theory and Calculation of the Phosphorescence Phenomenon2017In: Chemical Reviews, ISSN 0009-2665, E-ISSN 1520-6890, Vol. 117, no 9, p. 6500-6537Article, review/survey (Refereed)
    Abstract [en]

    Phosphorescence is a phenomenon of delayed luminescence that corresponds to the radiative decay of the molecular triplet state. As a general property of molecules, phosphorescence represents a cornerstone problem of chemical physics due to the spin prohibition of the underlying triplet-singlet emission and because its analysis embraces a deep knowledge of electronic molecular structure. Phosphorescence is the simplest physical process which provides an example of spin-forbidden transformation with a characteristic spin selectivity and magnetic field dependence, being the model also for more complicated chemical reactions and for spin catalysis applications. The bridging of the spin prohibition in phosphorescence is commonly analyzed by perturbation theory, which considers the intensity borrowing from spin-allowed electronic transitions. In this review, we highlight the basic theoretical principles and computational aspects for the estimation of various phosphorescence parameters, like intensity, radiative rate constant, lifetime, polarization, zero-field splitting, and spin sublevel population. Qualitative aspects of the phosphorescence phenomenon are discussed in terms of concepts like structure-activity relationships, donor-acceptor interactions, vibronic activity, and the role of spin-orbit coupling under charge-transfer perturbations. We illustrate the theory and principles of computational phosphorescence by highlighting studies of classical examples like molecular nitrogen and oxygen, benzene, naphthalene and their azaderivatives, porphyrins, as well as by reviewing current research on systems like electrophosphorescent transition metal complexes, nucleobases, and amino acids. We furthermore discuss modern studies of phosphorescence that cover topics of applied relevance, like the design of novel photofunctional materials for organic light-emitting diodes (OLEDs), photovoltaic cells, chemical sensors, and bioimaging.

  • 3. Baryshnikov, Gleb V.
    et al.
    Minaev, Boris F.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Pittelkow, Michael
    Nielsen, Christian B.
    Salcedo, Roberto
    Nucleus-independent chemical shift criterion for aromaticity in pi-extended tetraoxa[8]circulenes2013In: Journal of Molecular Modeling, ISSN 1610-2940, E-ISSN 0948-5023, Vol. 19, no 2, p. 847-850Article in journal (Refereed)
    Abstract [en]

    Recently synthesized pi-extended symmetrical tetraoxa[8]circulenes that exhibit electroluminescent properties were calculated at the density functional theory (DFT) level using the quantum theory of atoms in molecules (QTAIM) approach to electron density distribution analysis. Nucleus-independent chemical shift (NICS) indices were used to characterize the aromaticity of the studied molecules. The tetraoxa[8]circulene molecules were found to consist of two antiaromatic perimeters (according to the Huckel "4n" antiaromaticity rule) that include 8 and 24 pi-electrons. Conversely, NICS calculations demonstrated the existence of a common pi-extended system (distributed like a flat ribbon) in the studied tetraoxa[8]circulene molecules. Thus, these symmetrical tetraoxa[8]circulene molecules provide examples of diatropic systems characterized by the presence of induced diatropic ring currents.

  • 4.
    Baryshnikov, Gleb V.
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology. Tomsk State Univ, 36 Lenin Ave, Tomsk, Russia..
    Sunchugashev, Dmitry A.
    Tomsk State Univ, 36 Lenin Ave, Tomsk, Russia..
    Valiev, Rashid R.
    Tomsk State Univ, 36 Lenin Ave, Tomsk, Russia..
    Minaev, Boris F.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Centres, Albanova VinnExcellence Center for Protein Technology, ProNova.
    Vibronic absorption spectra of the angular fused bisindolo- and biscarbazoloanthracene blue fluorophores for OLED applications2018In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 513, p. 105-111Article in journal (Refereed)
    Abstract [en]

    An in-depth analysis of the vibronic absorption spectra for the recently synthesized blue-fluorescent OLED emitters bis[(1,2)(5,6)]indoloanthracene and biscarbazolo[3,4-a:3',4'-h]anthracene has been carried out computationally at the density functional theory level within the Franck-Condon approximation. These molecules are characterized by extended and rich electronic absorption spectra with most absorption bands being of vibronic origin. The first excited singlet state of bis[(1,2)(5,6)]indoloanthracene compound demonstrates a clear observable double-peak vibronic progression for two different active modes in the absorption spectrum, while the S-2 state is vibronically inactive. In contrast, for the larger biscarbazolo[3,4-a:3',4'-h]anthracene compound the S-0 -> S-2 transition demonstrates well-resolved intense vibronic bands which overlap the less intense progressions of few modes in the S-0 -> S-1 transition. We have also found, that even the higher-lying and very intense S-0 -> S-4 and S-0 -> S-5 transitions for bis[(1,2)(5,6)]indoloanthracene and biscarbazolo[3,4-a:3',4'-h]anthracene, respectively, are characterized by clear vibronic progressions in excellent agreement with experimental spectra.

  • 5.
    Baryshnikov, Gleb V.
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. Bogdan Khmelnitsky National University, Ukraine; Tomsk State University, Russian Federation.
    Valiev, Rashid R.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. Tomsk State University, Russian Federation; Tomsk Polytechnic University, Russian Federation.
    Minaev, Boris F.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. Bogdan Khmelnitsky National University, Ukraine; Tomsk State University, Russian Federation.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    A computational study of aromaticity and photophysical properties of unsymmetrical azatrioxa[8]circulenes2017In: New Journal of Chemistry, ISSN 1144-0546, E-ISSN 1369-9261, Vol. 41, no 7, p. 2717-2723Article in journal (Refereed)
    Abstract [en]

    Owing to their potential use in organic light-emitting diodes and field-effect transistors we present a theoretical study of a series of unsymmetrical azatrioxa[8]circulenes in order to explain the impact of outer substituents and benzoannelation on photophysical constants and aromaticity of these compounds in terms of spin-orbit coupling perturbation and magnetically-induced ring currents. It is argued that the S1-Tn inter-system crossing processes constitute the main deactivation pathways for the fluorescence quenching, something that is supported by a good agreement obtained with experimental data on fluorescence quantum yields. The concept of the gauge-including magnetically induced currents has been applied in order to estimate the role of substituents and benzoannelated fragments on the aromaticity and particularly on the overall balance between the diatropic “aromatic” and paratropic “antiaromatic” current strengths. While a variation of the substituents in the outer perimeter of the studied circulenes does not provide a clear effect on their aromaticity, it is demonstrated that an additional benzoannelation (π-extension) of the azatrioxa[8]circulene macrocycle induces a significant aromaticity enhancement.

  • 6.
    Baryshnikov, Glib V.
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. Bogdan Khmelnitsky Cherkasy National University, Ukraine.
    Bondarchuk, S. V.
    Minaeva, V. A.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Minaev, Boris F.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. Bogdan Khmelnitsky Cherkasy National University, Ukraine.
    Solvatochromic effect in absorption and emission spectra of star-shaped bipolar derivatives of 1,3,5-triazine and carbazole. A time-dependent density functional study2017In: Journal of Molecular Modeling, ISSN 1610-2940, E-ISSN 0948-5023, Vol. 23, no 2, article id 55Article in journal (Refereed)
    Abstract [en]

    A series of three star-shaped compounds containing both donor (carbazole) and acceptor (2,4,6-triphenyl-1,3,5-triazine) moieties linked through various linking bridges was studied theoretically at the linear response TD-DFT level of theory to describe their absorption and fluorescence spectra. The concept of a localized charge-transfer excited state has been applied successfully to explain the observed strong solvatochromic effect in the emission spectra of the studied molecules, which can be utilized for the fabrication of color tunable solution-processable OLEDs. The concept is in particularly applicable to donor–acceptor species with a C3 symmetry point group where the static dipole moment changes dramatically upon electronic excitation. An important peculiarity of the studied molecules is that they are characterized by non-zero values of the HOMO and LUMO orbitals in the same common part of molecular space that provides a large electric dipole transition moment for both light absorption and emission. [Figure not available: see fulltext.]

  • 7.
    Baryshnikov, Glib V.
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. V. D. Kuznetsov Siberian Physical-Technical Institute at National Research Tomsk State University, Russian Federation.
    Minaev, Boris F.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. V. D. Kuznetsov Siberian Physical-Technical Institute at National Research Tomsk State University, Russian Federation.
    Baryshnikova, A. A.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Anion-induced exchange interactions in binuclear complexes of Cu(II) with flexible hexadentate bispicolylamidrazone ligands2016In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 661, p. 48-52Article in journal (Refereed)
    Abstract [en]

    Two recently synthesized copper(II) complexes with spacer-armed bispicolylamidrazone ligands have been theoretically studied at the density functional theory (DFT) level accounting for empirical dispersion correction and intrinsic anionic environment by perchlorate ions. The exchange parameter between the open-shell singlet and triplet states of the studied complexes has been estimated by broken symmetry DFT calculations. The mechanism of spin-spin exchange interaction between the unpaired electrons via the σ-bond aliphatic chain (Gusev et al., 2015) is confirmed. Instead, a anion-induced mechanism is proposed which means that the anionic grid participates in the exchange interaction between the unpaired electrons.

  • 8.
    Baryshnikov, Glib V.
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Minaeva, Valentina A.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Minaev, Boris F.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Grigoras, M.
    The Electronic Structure and Spectra of Triphenylamines Functionalized by Phenylethynyl Groups2018In: Optics and Spectroscopy, ISSN 0030-400X, E-ISSN 1562-6911, Vol. 124, no 1, p. 57-64Article in journal (Refereed)
    Abstract [en]

    We study the features of the electronic structure and the IR, UV, and visible spectra of a series of triphenylamines substituted with phenylethynyl groups. The analysis is performed at the level of the density functional theory (DFT) and its nonstationary version in comparison with the experimental data of IR and electron spectroscopy. It is shown that, in the excited state, there is a change in the alternation of single, double, and triple bonds in accordance with the character of bonding and antibonding in the lowest vacant molecular orbital. The gradual introduction of additional phenylethynyl groups does not cause frequency shifts in the IR spectra of the molecules under study, but significantly affects the intensity of the corresponding IR bands. A similar effect is also observed in the electronic-absorption spectra of these compounds. This can be used for optical tuning of triphenylamines as promising materials for organic light-emitting diodes and solar cells.

  • 9. Bondarchuk, S. V.
    et al.
    Minaev, Boris F.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Two-dimensional honeycomb (A7) and zigzag sheet (ZS) type nitrogen monolayers. A first principles study of structural, electronic, spectral, and mechanical properties2017In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 133, p. 122-129Article in journal (Refereed)
    Abstract [en]

    Two single-bonded 2D nitrogen allotropes of the honeycomb (A7) and zigzag sheet (ZS) topology have been calculated using density functional theory (DFT). The optical (vibrational, absorption, nuclear magnetic resonance), thermodynamic and elastic properties of the A7 and ZS sheets have been calculated for the first time. The band structure calculation have revealed a semiconducting nature of the ZS sheet with a direct gap of 1.246 eV, while the A7 monolayer behaves as an insulator with an indirect gap of 3.842 eV. Phonon dispersion calculations have justified these structures as vibrationally stable 2D materials. The IR spectroscopy completely failed in the characterization of the studied materials, while the Raman spectroscopy can be effectively applied for the experimental spectral identification. The absorption spectra demonstrate complete opacity of the A7 and ZS monolayers to the UV irradiation only above ca. 9 and 6 eV, respectively. Thus, the studied materials are expected to be transparent to the visible light. The electron arrangement of the nitrogen nuclei in the studied polynitrogen sheets is denser compared to the N2 molecule which follows from the calculation of the values of magnetic shielding tensors. The elastic constants reveal a robust mechanical stability of the studied 2D nitrogen allotropes. The Young moduli values are only twice as lower than that of the graphene molecule.

  • 10. Bondarchuk, S. V.
    et al.
    Minaev, Boris
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Fesak, A. Y.
    Theoretical study of the triplet state aryl cations recombination: A possible route to unusually stable doubly charged biphenyl cations2013In: International Journal of Quantum Chemistry, ISSN 0020-7608, E-ISSN 1097-461X, Vol. 113, no 24, p. 2580-2588Article in journal (Refereed)
    Abstract [en]

    The self-recombination reactions of 4-aminophenyl cations and parent phenyl cations, each in ground triplet states, are studied within the framework of density functional theory. Only the total zero spin (singlet state) is chosen, as the quintet and triplet counterparts are nonreactive in these systems. The recombination products are the benzidine and biphenyl doubly charged cations. These species are unexpectedly stable. The transition state of the 4-aminophenyl cations reaction is located at the distance of about 4.0 Å between the ipso-carbon atoms. The activation barrier is predominantly formed by electrostatic repulsion between two cations and is estimated to be 27.6 kcal mol-1 [B3LYP/6-311+G(d,p)]. Similar results are obtained for the phenyl cations recombination. The general importance of the participation of other aryl cations in analogous organic reactions is discussed. © 2013 Wiley Periodicals, Inc. The chemical reactivity of diamagnetic molecules is largely determined by the properties of their triplet excited states rather than their closed-shell ground singlet state. As an example of this type of "spin-catalysis," the self-recombination reaction of the triplet state 4-aminophenyl cations leads to the formation of the benzidine dication. The corresponding transition state is "reactant-like" and located at the CipsoCipso interatomic distance of 4.0 Å.

  • 11. Bondarchuk, Sergey V.
    et al.
    Minaev, Boris F.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    Density functional study of ortho-substituted phenyl cations in polar medium and in the gas phase2011In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 389, no 1-3, p. 68-74Article in journal (Refereed)
    Abstract [en]

    Density functional theory (DFT) calculations of several 2-X-substituted phenyl cations (X = 2-CHO, 2-CH(2)OH, 2-CHS, 2-CH=NH, 2-OCH=NH, 2-SCH=NH, 2-CH=CH-CH=CH(2), 2-CH=CH(2) and 2-NO(2)) have been carried out in the gas phase and in acetonitrile (MeCN) at the B3LYP/6-31G(d,p) level of theory. The stationary point geometry of these aryl cations have been found to be in strong dependency of the medium. In the gas phase, unexpected behavior of considered aryl cations takes place resulting in the rearrangement or ring closure reaction. Such the cyclization reaction is proceeding via the nearby atom of the substituent which appears in relative vicinity (up to similar to 3 angstrom) to the cationic center. Only in the case of 2-NO(2) derivative, the geometry optimization has lead to rearranged quazi-quinoid structure of the cation that, obviously, takes place because of instability of the ring formed. Scan of the potential energy surface (PES) of 2-nitrophenyl cation has displayed no any reaction path leading toward the rearranged structure. Thus, the impossibility of existing of the singlet state of 2-nitrophenyl cation in the gas phase has been offered. The singlet-triplet transition of 2-nitrophenyl cation has been discussed in terms of the spin-orbit coupling (SOC) effects.

  • 12. Bondarchuk, Sergey V.
    et al.
    Minaev, Boris F.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. Bogdan Khmelnitsky Cherkasy Natl Univ, Ukraine.
    DFT design of polyguanidine - a unique two-dimensional material with high-energy density2017In: Molecular Physics, ISSN 0026-8976, E-ISSN 1362-3028, Vol. 115, no 19, p. 2423-2430Article in journal (Refereed)
    Abstract [en]

    We report herein a theoretical prediction and characterisation of a new two-dimensional (2D) material based on energetic polyguanidine. The structure represents a hexagonal type lattice of the P6/m space group. The material is dynamically and mechanically stable. Highly accurate band structure calculation with hybrid functional HSE06 reveals a tiny direct band gap being equal to 0.181 eV. We provide an additional spectral characterisation of the 2D polyguanidine substance including UV-vis, nuclear magnetic resonance and nuclear quadrupolar resonance parameters. The electron transport properties of a 26.6 angstrom wide polyguanidine ribbon are calculated in terms of tight-binding density functional theory approach. The predicted 2D material is also analysed by means of Quantum Theory of Atoms in Molecules and the aromatic character of the formed rings is estimated using nucleus-independent chemical shifts quantities.

  • 13. Bondarchuk, Sergey V.
    et al.
    Minaev, Boris F.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Super high-energy density single-bonded trigonal nitrogen allotrope-a chemical twin of the cubic gauche form of nitrogen2017In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 19, no 9, p. 6698-6706Article in journal (Refereed)
    Abstract [en]

    A new ambient- pressure metastable single- bonded 3D nitrogen allotrope (TrigN) of trigonal symmetry (space group R(-)3) was calculated using density functional theory (DFT). A comprehensive characterization of this material, comprising thermodynamic, elastic, and spectral (vibrational, UV-vis absorption, and nuclear magnetic resonance) properties, was performed. Using high-throughput band structure calculation, the TrigN phase was characterized as an insulator with an indirect band gap of 2.977 eV. Phonon dispersion calculations justified that this structure is vibrationally stable at ambient pressure. The calculated Raman activities at the Gamma-point demonstrated a rich pattern, whereas no relatively intense transitions were observed in its IR absorption spectrum. The TrigN material is almost transparent to visible light as well as to ultraviolet A and B. The main absorption peaks appeared within the range of 50-200 nm. The electron arrangement of the nitrogen nuclei in the studied nitrogen allotrope is much denser compared to that of the molecular nitrogen, which is in agreement with the calculated magnetic shielding tensor values. Robust mechanical stability is revealed from the elastic constants calculation. Due to strong anisotropy, the values of the Young's moduli vary from 281 to 786 GPa. A huge amount of internal energy is enclosed in the TrigN material. Upon decomposition to molecular nitrogen, the energy release is expected to be 11.01 kJ g(-1) compared to the value of 10.22 kJ g(-1) for the cubic gauche form of nitrogen. The TrigN allotrope possesses unique detonation characteristics with a detonation pressure of 146.06 GPa and velocity of 15.86 km s(-1).

  • 14.
    Bondarchuk, Sergey V.
    et al.
    Bogdan Khmelnitsky Cherkasy National University, Ukraine.
    Minaev, Boris F.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. Bogdan Khmelnitsky Cherkasy National University, Ukraine .
    Theoretical Study of Relationships between Structural, Optical, Energetic, and Magnetic Properties and Reactivity Parameters of Benzidine and Its Oxidized Forms2014In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 118, no 38, p. 8872-8882Article in journal (Refereed)
    Abstract [en]

    Structural, topological, optical, energetic, and magnetic properties and reactivity parameters of benzidine, its radical cation, and its dication as well as molecular complexes of the benzicline dication with the F-, Cl-, Br-, I-, NO3-, HSO4-, and H2PO4- anions were calculated at the B3LYP/6-311++G(2d,2p) level of theory in the CH2Cl2 medium. The CAM-B3LYP functional (as the most reliable one) and the 6-311++G(3df,3pd) basis set were used for the UV-vis absorption spectra prediction. The obtained spectral results are in a good agreement with available experimental data. A number of the calculated global and local molecular properties, including several recently developed ones, (in general, more than 20 parameters), namely, lambda(max), the bond lengths and orders (l and L-A,L-B), adiabatic ionization energy (IEad), global electrophilicity index (omega), condensed electrophilic Fukui functions (f(+)) and dual descriptor (Delta f(A)), van der Waals molecular volume, nuclear independent chemical shifts (NICS) and QTAIM topological parameters were estimated in the critical points of the C(1)-C(1'), C(2)-C(3), and C(4)-N bonds as well as at the ring critical point. These quantities were found to be in a strong linear dependence (R-2 > 0.99 in most cases) with the number of detached electrons (N-el) from the benzidine molecule up to formation of the dication (N-el = 2). On one hand, a position of the long-wave absorption band (lambda(CT)) corresponding to the anion-to-cation charge transfer in the neutral complexes of the benzidine dication with anions, correlates with the Mulliken electronegativity of the anion (R-2 = 0.8646) and its adiabatic ionization energy (R-2 = 0.8054). On the other hand, the correlations with the anion charge in the complexes and the anion isotropic polarizability are rather poor (R-2 = 0.6392 and 0.3470, respectively). On the ground of the obtained strong relationships, one may recommend the calculated molecular properties as potentially preferable descriptors for the benzidine-based compounds in terms of the QSAR methodology.

  • 15.
    Bondarchuk, Sergey V.
    et al.
    Bogdan Khmelnitsky Cherkasy National University, Ukraine.
    Minaev, Boris F.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. Bogdan Khmelnitsky Cherkasy National University, Ukraine.
    Thermally accessible triplet state of pi-nucleophiles does exist. Evidence from first principles study of ethylene interaction with copper species2015In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 5, no 15, p. 11558-11569Article in journal (Refereed)
    Abstract [en]

    Three different models of ethylene interaction with copper species, namely, the Cu(100) surface, odd-numbered copper clusters C2H4/Cu-n (where n = 3, 7, 11, 15, 17, 19, 21, 25 and 27) and atomic copper C2H4/Cu were studied theoretically. It was found that the ethylene molecule possesses three different types of bonding depending on the presence of the unpaired spin on the reacting copper atom. These bonding structures demonstrate different types of band gap (bulk) or SOMO-LUMO gaps (cluster/atom), where SOMO stands for the singly occupied and LUMO means the lowest unoccupied molecular orbitals of the copper species. The obtained results are in good agreement with the previous experimental and computational results on the structural, spectral and energetic properties of the studied species. The bulk copper and sub-nanosized clusters (n > 7) build up the mono-pi-bonded ground state complexes with ethylene where the latter species possesses the C-2v symmetry. The single-atom complex C2H4/Cu forms the CS-symmetrical ground state (X) over tilde (2)A' and the excited B-2(2) and B-4 state complexes of the C-2v and C-2 symmetry, respectively. The (X) over tilde (2)A' state complex is mono-sigma-bonded and involves the singlet ethylene moiety. The more tightly bound excited B-2(2) complex has the di-sigma-bonded structure and corresponds to the triplet ethylene. The adiabatic energy difference between the B-2(2) and (X) over tilde (2)A' states is equal to 10.8 kcal mol(-1) and can be ascribed to the singlet-triplet splitting of the ethylene moiety interacting with copper. The QTAIM analysis supports the coordination type of the Cu-C bonds in all the studied complexes. Formation of the C2H4/Cu(100), C2H4/Cu-n and C2H4/Cu species is in accord with the well-known Dewar-Chatt-Duncanson model, in such a way that the opposing sigma-donation step yields the ground state complex ((X) over tilde (2)A'), while the subsequent more expensive supporting pi*-back donation step provides the excited B-2(2) state complex. In the present paper we have developed a computational procedure to optimize the latter complex.

  • 16. Bondarchuk, Sergey V.
    et al.
    Minaev, Boris F.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. Bogdan Khmelnitsky Cherkasy National University, Ukraine.
    Two isomeric solid carbon nitrides with 1:1 stoichiometry which exhibit strong mechanical anisotropy2017In: New Journal of Chemistry, ISSN 1144-0546, E-ISSN 1369-9261, Vol. 41, no 21, p. 13140-13148Article in journal (Refereed)
    Abstract [en]

    Two isomeric layered carbon nitride phases in a trigonal crystal system with 1:1 stoichiometry, NCCN and NCNC (space group P3m1), are studied using first principles calculations and quantum theory of atoms in molecules (QTAIM) analysis, where the latter phase is predicted for the first time. Comprehensive characterization of these materials is performed to determine their thermodynamic, elastic and spectral (vibrational, UV-vis and NMR) properties. High-throughput scheme for band structure calculations along with the accurate hybrid functional HSE06 provide the indirect band gaps of 3.142 eV (NCNC) and 5.021 eV (NCCN). Phonon dispersion calculations prove that the studied materials are dynamically stable at ambient pressure. The NCCN phase demonstrates a poor spectral pattern on infrared (IR) intensities and Raman activities, whereas the NCNC polymorph is expected to be effectively detectable by both spectral techniques. The UV-vis spectra of the studied phases display absorption bands between ca. 50-150 nm, which indicates that these isomers are transparent to visible light. Elastic constant calculations indicate strong anisotropy of their Young's moduli. In the [1 0 0] equivalent to [0 1 0] plane directions the modulus values are 914.6 GPa (NCNC) and 865.1 GPa (NCCN). In the [0 0 1] direction, which is perpendicular to the layer plane, the Young's moduli are much smaller and equal to 73.3 GPa and 58.4 GPa for NCNC and NCCN, respectively. The exfoliation energies are expected to be about 3 (NCNC) and 2 (NCCN) times higher than those of graphite.

  • 17. Bondarchuk, Sergey V.
    et al.
    Smalius, Victor V.
    Minaev, Boris F.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. Bogdan Khmelnitsky Cherkasy National University, Ukraine .
    A combined experimental and density functional study of 1-(arylsulfonyl)-2-R-4-chloro-2-butenes reactivity towards the allylic chlorine2015In: Journal of Physical Organic Chemistry, ISSN 0894-3230, E-ISSN 1099-1395, Vol. 28, no 6, p. 403-413Article in journal (Refereed)
    Abstract [en]

    Nucleophilic substitution and dehydrochlorination reactions of a number of the ring-substituted 1-(arylsulfonyl)-2-R-4-chloro-2-butenes are studied both experimentally and theoretically. The developed synthetic procedures are characterized by a general rapidity, cheapness, and simplicity providing moderate to high yields of 1-arylsulfonyl 1,3-butadienes (48-95%), 1-(arylsulfonyl)-2-R-4-(N,N-dialkylamino)-2-butenes (31-53%), 1-(arylsulfonyl)-2-R-2-buten-4-ols (37-61%), and bis[4-(arylsulfonyl)-3-R-but-2-enyl]sulfides (40-70%). The density functional theory B3LYP/6-311++G(2d,2p) calculations of the intermediate allylic cations in acetone revealed their high stability occurring from a resonance stabilization and hyperconjugation by the SO2Ar group. The reactivity parameters estimated at the bond critical points of the diene/allylic moiety display a high correlation (R-2>0.97) with the Hammett (sigma(p)) constants. 1-Arylsulfonyl 1,3-butadienes are characterized by a partly broken conjugated system, which follows from analysis of the two-centered delocalization () and localization () index values. The highest occupied molecular orbital energies of 1-arylsulfonyl 1,3-butadienes are lower than those of 1,3-butadiene explaining their low reactivity towards the Diels-Alder condensation.

  • 18. Grybauskaite-Kaminskiene, Gintare
    et al.
    Ivaniuk, Khrystyna
    Bagdziunas, Gintautas
    Turyk, Pavlo
    Stakhira, Pavlo
    Baryshnikov, Gleb V.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. Bohdan Khmelnytsky National University, Ukraine.
    Volyniuk, Dmytro
    Cherpak, Vladyslav
    Minaev, Boris F.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. Bohdan Khmelnytsky National University, Ukraine.
    Hotra, Zenon
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. Siberian Federal University, Russian Federation.
    Grazulevicius, Juozas Vidas
    Contribution of TADF and exciplex emission for efficient "warm-white" OLEDs2018In: Journal of Materials Chemistry C, ISSN 2050-7526, E-ISSN 2050-7534, Vol. 6, no 6, p. 1543-1550Article in journal (Refereed)
    Abstract [en]

    The bicarbazole derivative 4,4'-(9H, 9'H-[3,3'-bicarbazole]-9,9'-diyl) bis(3-(trifluoromethyl) benzonitrile), denoted as pCNBCzoCF(3), was synthesized and tested for white OLED applications. pCNBCzoCF3 demonstrated an extremely small value of the singlet-triplet energy gap that caused intensive thermally activated delayed fluorescence (TADF). In addition, this compound is able to form exciplex-type excited states at the interface with star-shaped 4,40,400-tris[phenyl(m-tolyl) amino] triphenylamine (m-MTDATA). Combining the TADF emission of pCNBCzoCF3 with the exciplex emission from the pCNBCzoCF(3) m-MTDATA interface, we fabricated a number of highly efficient "warm-white'' OLEDs, the electroluminescence of which was close to candle emission. The best device demonstrated a very high brightness of 40 900 Cd m(-2) (at 15 V), current efficiency of 53.8 Cd A(-1) and power efficiency of 19.3 lm W-1, while the external quantum efficiency reached 18.8%. The fabricated devices demonstrated high emission characteristics even for the standard test at 1000 Cd m(-2) (current efficiency of 46.2 Cd A(-1), power efficiency of 10.6 lm W-1, EQE of 17.0%).

  • 19. Gusev, A. N.
    et al.
    Shul'gin, V. F.
    Braga, E. V.
    Nemec, I.
    Minaev, Boris F.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Baryshnikov, Gleb V.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Trávníček, Z.
    Ågren, Hans
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology. Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden.
    Eremenko, I. L.
    Lyssenko, K. A.
    Linert, W.
    Synthesis and photophysical properties of Zn(II) Schiff base complexes possessing strong solvent-dependent solid-state fluorescence2018In: Polyhedron, ISSN 0277-5387, E-ISSN 1873-3719, Vol. 155, p. 202-208Article in journal (Refereed)
    Abstract [en]

    The present article reports on the syntheses, crystal structures and luminescence properties of three solvate forms of a zinc(II) complex containing 4-{(E)-[(2-fluorophenyl)imino]methyl}-5-methyl-2-phenyl-2,4-dihydro-3H-pyrazol-3-one (HL). The reaction of zinc(II)acetate with the HL ligand in ethanol and acetonitrile led to the formation of two solvate analogues [Zn(L)2]·Solv (Solv – ethanol (1) and acetonitrile (2)). The properties of the [Zn(L)2]·Solv complexes were investigated by UV–Vis absorption and fluorescence emission spectroscopy, and the density functional theory calculations. Bader's topological analysis was performed to investigate the electronic peculiarities of Zn(II) polyhedra and non-covalent interactions within crystal packing of studied solvates.

  • 20.
    Gusev, Alexey
    et al.
    Russian Acad Sci, NS Kurnakov Inst Gen & Inorgan Chem, Moscow 119991, Russia. ryukova, Mariya.
    Braga, Elena
    Zamnius, Ekaterina
    Kiskin, Mikhail
    Kryukova, Mariya
    Baryshnikova, Alina
    Minaev, Boris F.
    Bohdan Khmelnytsky Natl Univ, Dept Chem & Nanomat Sci, UA-18031 Cherkassy, Ukraine.
    Baryshnikov, Gleb V.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology. Bohdan Khmelnytsky Natl Univ, Dept Chem & Nanomat Sci, UA-18031 Cherkassy, Ukraine.
    Ågren, Hans
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Linert, Wolfgang
    Structure and excitation-dependent emission of novel zinc complexes with pyridyltriazoles2019In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 9, no 38, p. 22143-22152Article in journal (Refereed)
    Abstract [en]

    A series of Zn(ii) complexes with 5-(4-R-phenyl)-3-(pyridin-2-yl)-1,2,4-triazoles have been synthesized and subsequently characterized by single crystal X-ray diffraction, H-1-NMR, FT-IR spectroscopy, elemental analyses, ESI-MS, and PXRD. The X-ray diffraction analyses revealed that the complexes have a similar molecular structure and their supramolecular frameworks are constructed by hydrogen bonds and pi center dot center dot center dot pi interaction scaffolds. Upon irradiation with UV light, the studied complexes display deep blue emission at 396-436 nm in the solid state. The compounds show an unexpected excitation-dependent emission phenomenon which is detected by a change in the emission color (from blue to yellow) upon increase of the excitation wavelength. The conducted quantum-chemical calculations indicate that supramolecular differences in the single-crystal architecture of the synthesized complexes play a crucial role for this photophysical behaviour.

  • 21. Ivaniuk, K. B.
    et al.
    Baryshnikov, Glib V.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. Bohdan Khmelnytsky National University of Cherkasy, Ukraine.
    Stakhira, P. Y.
    Pedersen, S. K.
    Pittelkow, M.
    Lazauskas, A.
    Volyniuk, D.
    Grazulevicius, J. V.
    Minaev, Boris F.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. Khmelnytsky National University of Cherkasy, Ukraine.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. Siberian Federal University, Russia.
    New WOLEDs based on pi-extended azatrioxa[8]circulenes2017In: Journal of Materials Chemistry C, ISSN 2050-7526, E-ISSN 2050-7534, Vol. 5, no 17, p. 4123-4128Article in journal (Refereed)
    Abstract [en]

    New stable WOLEDs based on pi-extended azatrioxa[8]circulenes have been fabricated. Combining the own blue emission of the azatrioxa[8] circulenes with the yellow-green emission of the "m-MTDATA:azatrioxa[8]circulene'' exciplex a broad visible region, from 400 to 700 nm, is covered. The so constructed WOLEDs exhibit a luminance exceeding 23 700 cd m(-2) and an external quantum efficiency reaching 3%.

  • 22. Ivaniuk, K.
    et al.
    Cherpak, V.
    Stakhira, P.
    Baryshnikov, Gleb
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. Bohdan Khmelnytsky National University, Ukraine.
    Minaev, Boris
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. Bohdan Khmelnytsky National University, Ukraine.
    Hotra, Z.
    Turyk, P.
    Zhydachevskii, Y.
    Volyniuk, D.
    Aksimentyeva, O.
    Penyukh, B.
    Lazauskas, A.
    Tamulevičius, S.
    Grazulevicius, J. V.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. Siberian Federal University, Russian Federation.
    BaZrO3 perovskite nanoparticles as emissive material for organic/inorganic hybrid light-emitting diodes2017In: Dyes and pigments, ISSN 0143-7208, E-ISSN 1873-3743, Vol. 145, p. 399-403Article in journal (Refereed)
    Abstract [en]

    In the present work we have demonstrated double-channel emission from organic exciplexes coupled to inorganic nanoparticles. The process is demonstrated by yellow-green emission in light-emitting diodes based on organic exciplexes hybridized with perovskite-type dispersed BaZrO3 nanoparticles. Such double-channel emission provides a broadening of the electroluminescence spectrum and a resultant yellow-green emission color of the device. We have realized an energy transfer from the exciplexes arranged by the interface between two organic layers and the spherical-shaped BaZrO3 nanoparticles randomly deposited on the organic interface constructed of the tris(4-carbazoyl-9-ylphenyl)amine and 4,7-diphenyl-1,10-phenanthroline molecules. The fabricated device exhibits a current efficiency value of 3.88 C d/A, maximum brightness of 3465 cd/m2 (at 15 V), and external quantum efficiency of about 1.26%. In order to estimate the efficiency of the energy transfer from the exciplex to the BaZrO3 nanoparticles we have applied the Förster model for the dipole-dipole energy transfer accounting for the mutual overlap of the exciplex emission spectrum and the absorption spectrum of the BaZrO3 nanoparticles.

  • 23.
    Jansson, Emil
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Minaev, Boris
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Schrader, Sigurd
    echnische Fachhochschule Wildau, University of Applied Sciences.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Time-dependent density functional calculations of phosphorescence parameters for fac-tris(2-phenylpyridine) iridium2007In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 333, no 03-feb, p. 157-167Article in journal (Refereed)
    Abstract [en]

    fac-Tris(2-phenylpyridine) iridium [fac-Ir(PPY)(3)] produces strong phosphorescence and has therefore been used as materials in organic light emitting diodes to overcome the efficiency limit imposed by the formation of triplet excitons. Accounting for this circumstance we present in this paper a theoretical study of phosphorescence in the Ir(PPY)(3) complex. The spin-orbit coupling effects and the radiative lifetime in the high temperature limit (T) are calculated by time-dependent density functional theory using quadratic response technology in order to elucidate the main mechanism of the phosphorescence. It is found that the orbital structure of the T, state has a localized character and that the T1 -> S0 transition is determined mostly by charge transfer from one of the ligands to the metal. At the vertical S-0-T-1 excitation the triplet state is highly delocalized among all three ligands and has a mixed pi pi* and metal-to-ligand charge transfer character. The intensity borrowing from the S-0 to S-5 transitions is mostly responsible for the strong phosphorescence emission from the x and y spin sublevels. Our results concord with the experimental data on temperature and magnetic field dependence of the phosphorescence kinetics. The calculated radiative lifetime in the high temperature limit agrees well with the measured decay times (2 mu s) accounting for negligible non-radiative quenching of the lowest triplet state.

  • 24.
    Jansson, Emil
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    Norman, Patrick
    Linköpings Universitet.
    Minaev, Boris
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    Evaluation of low-scaling methods for calculation of phosphorescence parameters2006In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 124, no 11Article in journal (Refereed)
    Abstract [en]

    In order to find a methodology that is a compromise between favorable computational scaling and tolerable errors, a series of nonrelativistic approaches for the calculation of radiative phosphorescence lifetimes are benchmarked against fully relativistic four-component results. The study of the a (3)A(2)-X (1)A(1) transition intensity in the series of H2CX molecules, where X is a chalcogene atom, X={O,S,Se,Te}, indicates a general good agreement between fully relativistic four-component and nonrelativistic perturbation-theoretical calculations. Among the nonrelativistic approaches, the scaled-charge spin-orbit operator approach is recognized as to provide transition matrix elements that are in good agreement with those obtained with the more elaborate Breit-Pauli and atomic mean field spin-orbit operators. This finding supports phosphorescence calculations using the available linear scaling technology for large complexes and, together with effective-core potentials, large complexes including heavy elements.

  • 25.
    Karaush, N. N.
    et al.
    Bohdan Khmelnytsky Natl Univ, Dept Chem & Nanomat Sci, UA-18031 Cherkassy, Ukraine..
    Minaeva, V. A.
    Bohdan Khmelnytsky Natl Univ, Dept Chem & Nanomat Sci, UA-18031 Cherkassy, Ukraine..
    Baryshnikov, Gleb V.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology. Bohdan Khmelnytsky Natl Univ, Dept Chem & Nanomat Sci, UA-18031 Cherkassy, Ukraine.
    Minaev, Boris F.
    Bohdan Khmelnytsky Natl Univ, Dept Chem & Nanomat Sci, UA-18031 Cherkassy, Ukraine.
    Ågren, Hans
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology. Uppsala Univ, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden..
    Identification of tautomeric intermediates of a novel thiazolylazonaphthol dye - A density functional theory study2018In: Spectrochimica Acta Part A - Molecular and Biomolecular Spectroscopy, ISSN 1386-1425, E-ISSN 1873-3557, Vol. 203, p. 324-332Article in journal (Refereed)
    Abstract [en]

    The recently synthesized thiazolylazo dye, 1-(5-benzy1-1,3-thiazol-2-yl)diazenyllnaphthalene-2-ol called shortly BnTAN, is studied by density functional theory (DFT) in three tautomeric forms in order to explain the available H-1 NMR, UV-Vis and FTIR spectra. An experimentally observed IR band at 1678 cm(-1), assigned to the C=O bond stretching vibration, supports the notion that BnTAN retains in the less stable keto-form even in the solid state due to an ultrafast single-coordinate intramolecular proton transfer. This finding is also in a good agreement with an X-ray crystallography analysis which indicates an intermediate position of the proton between the OH and -N=N-groups. Calculations also show that some experimentally observed H-I NMR signals could be considered as being averaged values between theoretically calculated chemical shifts for the corresponding protons in the keto- and enol-tautomers. At the same time the UV-Vis spectra are almost insensitive to the tautomerization processes as the main single band absorption at 500 nm is present in all tautomers according to our TD DFT simulations. The minor differences in spectral features of the long-wavelength visible region are also noted and discussed with respect to the manifestation of the less stable tautomer form.

  • 26. Karaush, Nataliya N.
    et al.
    Baryshnikov, Gleb V.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Minaeva, Valentina A.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Minaev, Boris F.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Recent progress in quantum chemistry of hetero[8]circulenes2017In: Molecular Physics, ISSN 0026-8976, E-ISSN 1362-3028, Vol. 115, no 17-18, p. 2218-2230Article in journal (Refereed)
    Abstract [en]

    This mini-review presents recent advances in theory of electronic and spectral properties of hetero[8]circulenes used as promising fluorescent emitters for organic light-emitting diodes. Special attention is paid to the possibility of their further functionalisation into one-dimensional and two-dimensional (2D) materials. Such materials are predicted to be useful ambipolar organic semiconductors showing high charge carrier mobility. The porous structure of hetero[8]circulene-based nano-arrays can also provide suitable hydrogen storage materials, biomimetic-type nanopores and ionic channels. They serve as a good example of the density functional theory application for design of stable 2D structures, which extends the family of graphene-like materials. [GRAPHICS] .

  • 27. Litvin, Valentina A.
    et al.
    Minaev, Boris F.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    The size-controllable, one-step synthesis and characterization of gold nanoparticles protected by synthetic humic substances2014In: Materials Chemistry and Physics, ISSN 0254-0584, E-ISSN 1879-3312, Vol. 144, no 1-2, p. 168-178Article in journal (Refereed)
    Abstract [en]

    In this paper we demonstrate the use of synthetic humic substances (HSs) in the synthesis of gold nanoparticles in which the unprecedented control of particle size and shape is achieved by varying the experimental conditions. In this reaction, the synthetic HSs are used as a reductive and protective reagent. A number synthetic HSs from different fenol precursors are tested. The nanoparticles formation processes were monitored by UV-visible spectroscopy, and the results were analyzed by transmission electron microscopy and X-ray diffraction. The preference of synthetic HSs over natural HSs is determined by a standardization problem resolution due to the strict control of the HSs formation conditions that expand the areas of application of the gold nanoparticles fabricated with such technique. These nanodispersions are aggregately stable for more than one year. The possible formation mechanism of primary gold nanoclusters is proposed.

  • 28.
    Minaev, Boris
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    Ab initio study of low-lying triplet states of the lithium dimer2005In: Spectrochimica Acta Part A - Molecular and Biomolecular Spectroscopy, ISSN 1386-1425, E-ISSN 1873-3557, Vol. 62, no 4-5, p. 790-799Article in journal (Refereed)
    Abstract [en]

    Observation of Bose-Einstein condensation in Li-7(2) initiated the interest in the scattering length of two ground state lithium atoms when they approach each other as a radical pair triplet a(3)Sigma(u)(+) state. But some properties of this state are still unknown. In present work, a number of low-lying triplet states of lithium molecule are calculated by multi-configuration self-consistent field (MCSCF) and response techniques with account of spin-orbit coupling, spin-spin coupling and some other magnetic perturbations. The singlet-triplet transition probabilities to the ground state are also presented. Most results are connected with the weakly bound lowest triplet a(3)Sigma(u)(+) state, whose radiative lifetime and spin-splitting are unknown so far in spite of its great importance in Bose-Einstein condensation. Calculations indicate that this state has a very small spin-splitting, lambda(ss) = -0.01 cm(-1), which is negligible in comparison with the line-width in experimental Fourier transform C spectra published so far. Similar splitting is obtained for the upper state of the 1(3)Sigma(g)(+)-a(3)Sigma(u)(+) transition. This is in agreement with experimental rovibronic analysis of the 1(3)Sigma(g)(+)- a(3)Sigma(u)(+) band system in which the triplet structure was not resolved. The radiative lifetime of the a(3)Sigma(u)(+) state is predicted to exceed 10 h.

  • 29.
    Minaev, Boris
    KTH, Superseded Departments, Biotechnology.
    Theoretical study of the external heavy atom effect on phosphorescence of free-base porphin molecule2004In: Spectrochimica Acta Part A - Molecular and Biomolecular Spectroscopy, ISSN 1386-1425, E-ISSN 1873-3557, Vol. 60, no 13, p. 3213-3224Article in journal (Refereed)
    Abstract [en]

    The radiative lifetime of phosphorescence of free-base porphin (H2P) molecule and its complexes with noble-gas atoms are calculated by time-dependent density functions theory (TD DFT) with quadratic response functions for account of spin-orbit coupling and electric dipole activity. The complexes with Ne, Ar, Kr, and Xe are used to simulate the external heavy atom (EHA) effect on phosphorescence of the H2P molecule in the corresponding noble gas matrices. The 133LYP functional and small basis set (3-21G) are used throughout the study and comparison of all complexes but other basis sets are also utilized to support the chosen approach. A slow radiative rate constant of free-base porphin phosphorescence (about 10(-3) S-1) is obtained with all basis sets being in the order of magnitude agreement with experimental estimations. A strong enhancement of the H2P phosphorescence rate (by 360 times) is calculated for Xe complex; while for Ne, Ar, and Kr complexes, the enhancement is equal to 1.1, 1.3, and 10.3 times, respectively. In these complexes, the noble gas atom is disposed at 3.6 Angstrom above the center of the porphin ring. In spite of shortcomings of the chosen simple model, the TD DFT calculations explain the most important features of the EHA effect on phosphorescence of free-base porphin. Calculations of the hypertine coupling tensors for all magnetic nuclei in the lowest triplet state of H2P molecule and its complexes with noble-gas atoms indicate an appreciable penetration of the spin density to the EHA region. This can be connected with the enhancement of spin-orbit coupling in the H2P molecule.

  • 30.
    Minaev, Boris
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Baryshnikov, Gleb
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Principles of phosphorescent organic light emitting devices2014In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 16, no 5, p. 1719-1758Article in journal (Refereed)
    Abstract [en]

    Organic light-emitting device (OLED) technology has found numerous applications in the development of solid state lighting, flat panel displays and flexible screens. These applications are already commercialized in mobile phones and TV sets. White OLEDs are of especial importance for lighting; they now use multilayer combinations of organic and elementoorganic dyes which emit various colors in the red, green and blue parts of the visible spectrum. At the same time the stability of phosphorescent blue emitters is still a major challenge for OLED applications. In this review we highlight the basic principles and the main mechanisms behind phosphorescent light emission of various classes of photofunctional OLED materials, like organic polymers and oligomers, electron and hole transport molecules, elementoorganic complexes with heavy metal central ions, and clarify connections between the main features of electronic structure and the photo-physical properties of the phosphorescent OLED materials.

  • 31.
    Minaev, Boris F.
    KTH, Superseded Departments, Biotechnology.
    Ab initio study of the ground state properties of molecular oxygen2004In: Spectrochimica Acta Part A - Molecular and Biomolecular Spectroscopy, ISSN 1386-1425, E-ISSN 1873-3557, Vol. 60, no 5, p. 1027-1041Article in journal (Refereed)
    Abstract [en]

    The electric and magnetic properties of the ground state of oxygen molecule are calculated by multiconfiguration self-consisted field (MCSCF) method and compared with experimental data: the quadrupole moment, polarizability, the O-17 nuclear quadrupole coupling constant, magnetizability tensor, nuclear spin-rotation Coupling constant and rotational g factor. The last two constants are calculated for all possible isotope modifications. The rotational, ESR and NMR spectra are discussed. Fermi-contact hyperfine coupling parameter is additionally estimated by different methods. The NMR chemical shielding tensor for (OO)-O-17-O-16 species at high temperature limit (without electron spin contribution) is predicted. Potential energy curves for 10 excited bound states and the internuclear distance dependence of the studied properties are also presented.

  • 32.
    Minaev, Boris F.
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Baryshnikov, Gleb V.
    Minaeva, Valentina A.
    Density functional theory study of electronic structure and spectra of tetraoxa[8]circulenes2011In: COMPUT THEOR CHEM, ISSN 2210-271X, Vol. 972, no 1-3, p. 68-74Article in journal (Refereed)
    Abstract [en]

    The electronic structure and spectra of a series of tetraoxa[8]circulene derivatives are studied by the density functional theory (DFT) calculations. The vertical transitions to the 30 lowest electronic excited states of the studied dyes are calculated by the time dependent (TD) DFT method in vacuum and solvent. The orbital nature and intensity of all observed absorption bands including vibronic satellites in the spectra of studied tetraoxa[8]circulene derivatives are explained. The reduction potentials are compared with electrochemical measurements and found to be relatively unaffected by the nature of the tetraoxa[8]circulene derivatives. We also obtained a good agreement between experimental fluorescence spectral characteristics of the tetraoxa[8]circulenes family and the theoretical analysis of the lowest singlet excited states wavefunctions. The nature of the fluorescent bands in the emission spectra is rather different for the generic tetraoxa[8]circulene and for its derivatives which agrees with the measured quantum yields and lifetimes. The 0-0 line of phosphorescence of the tetraoxa[8]circulene molecule ((3)A(2)g -> X(1)A(1g)) is predicted at 533 nm.

  • 33.
    Minaev, Boris F.
    et al.
    KTH, School of Biotechnology (BIO).
    Baryshnikov, Gleb V.
    Minaeva, Valentina A.
    Electronic structure and spectral properties of the triarylamine-dithienosilole dyes for efficient organic solar cells2012In: Dyes and pigments, ISSN 0143-7208, E-ISSN 1873-3743, Vol. 92, no 1, p. 531-536Article in journal (Refereed)
    Abstract [en]

    The recently synthesized high-performance triarylamine dyes with the dithienosilole pi-conjugated spacer for efficient organic solar cells are calculated at the density functional theory (DFT) level with the Bader approach for the quantum theory of atoms in molecule (QTAIM) analysis. The presence of stabilizing intramolecular hydrogen bonds and Van der Waals interactions in the dye molecules is predicted and the energies of these interactions are estimated. The electronic bands nature in absorption spectra of the dyes is determined by the time-dependent DFT calculations with a linear response methodology using B3LYP and BMK hybrid functionals. Relations between incident light absorption intensity in the first long-wavelength band of the dye, its polarization, HOMO-LUMO orbital nature and the driving force of electron injection to the semiconductor are discussed. (C) 2011 Elsevier Ltd. All rights reserved.

  • 34. Minaev, Boris F.
    et al.
    Murugan, N. Arul
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Dioxygen spectra and bioactivation2013In: International Journal of Quantum Chemistry, ISSN 0020-7608, E-ISSN 1097-461X, Vol. 113, no 14, p. 1847-1867Article in journal (Refereed)
    Abstract [en]

    Intensities of spin-forbidden transitions in electronic absorption and emission spectra of molecular oxygen are analyzed in order to understand the key mechanisms of spin-states mixing induced by spin-orbit coupling (SOC) and the ways to overcome spin prohibition for various photophysical and biochemical processes. Multireference configuration interaction calculations with SOC account are used to generalize spin-selection rules for the oxygen atmospheric and Herzberg bands in free O2 molecule and in collision complexes. Intensity enhancement of the atmospheric a1g X3 sigma g-, b1 sigma g+ X3 sigma g-, and Noxon b1 sigma g+ a1g transitions upon bimolecular collisions are compared with those for Herzberg III transitions A3u X3 sigma g-. Electric quadrupole, dipole, and magnetic approximations are used for transition probability calculations. Intensity distribution in rotational lines is also considered. With this background, we propose some simple spin-selection rules for dioxygen activation in enzymatic reactions. (c) 2013 Wiley Periodicals, Inc.

  • 35.
    Minaev, Boris F.
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Minaeva, Valentina
    Spin-orbit coupling effects in chemiluminescence2014In: Luminescence (Chichester, England Print), ISSN 1522-7235, E-ISSN 1522-7243, Vol. 29, p. 81-82Article in journal (Other academic)
  • 36.
    Minaev, Boris F.
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Ågren, Hans
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Minaeva, Valentina A.
    Spin-orbit coupling in enzymatic reactions and the role of spin in biochemistry2017In: Handbook of Computational Chemistry, Springer International Publishing , 2017, p. 1557-1587Chapter in book (Other academic)
    Abstract [en]

    We review the general concept of nonadiabatic quantum spin transitions in biochemistry. A few important examples are highlighted to illustrate the concept: the role of spin effects in oxidases, cytochromes, in dioxygen binding to heme, in photosynthesis, and in tentative models of consciousness. The most thoroughly studied of these effects are connected with dioxygen activation by enzymes. Discussion on the mechanisms of overcoming spin prohibitions in dioxygen reactions with flavin-dependent oxygenases and with hemoglobin and myoglobin is presented in some detail. We consider spin-orbit coupling (SOC) between the starting triplet state from the entrance channel of the O2 binding to glucose oxidase, to ferrous heme, and the final singlet open-shell state in these intermediates. Both triplet (T) and singlet (S) states in these examples are dominated by the radical-pair structures D+O2induced by charge transfer; the peculiarities of their orbital configurations are essential for the SOC analysis. An account of specific SOC in the open πg-shell of dioxygen helps to explain the probability of T-S transitions in the active site near the transition state. Simulated potential energy surface cross-sections along the reaction coordinates for these multiplets, calculated by density functional theory, agree with the notion of a relatively strong SOC induced inside the oxygen moiety by an orbital angular momentum change in the πg-shell during the T-S transition. The SOC model explains well the efficient spin inversion during the O2 binding with heme and glucose oxidase, which constitutes a key mechanism for understanding metabolism. Other examples of nontrivial roles of spin effects in biochemistry are briefly discussed. 

  • 37. Minaev, Boris
    et al.
    Li, Xin
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    Ning, Zhijun
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    Tian, He
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    Organometallic Materials for Electroluminescent and Photovoltaic Devices2011In: Organic Light Emitting Diode: Material, Process and Devices / [ed] A. Lazinica, INTECH, 2011, p. 61-100Chapter in book (Other academic)
  • 38.
    Minaev, Boris
    et al.
    KTH, Superseded Departments, Biotechnology.
    Loboda, Oleksandr
    KTH, Superseded Departments, Biotechnology.
    Vahtras, Olav
    KTH, Superseded Departments, Biotechnology.
    Ruud, K.
    Ågren, Hans
    KTH, Superseded Departments, Biotechnology.
    Solvent effects on optically detected magnetic resonance in triplet spin labels2004In: Theoretical Chemistry accounts, ISSN 1432-881X, E-ISSN 1432-2234, Vol. 111, no 2-6, p. 168-175Article in journal (Refereed)
    Abstract [en]

    We have calculated solvent effects on the zero-field splitting (ZFS) constants induced by electron spin-spin coupling (SSC) in the low-lying triplet states of azaaromatic molecules in solutions using multiconfiguration self-consistent-field wave functions and the polarizable continuum model. The second-order spin-orbit coupling (SOC) contribution to the splitting of the (3)pipi(*) states is found to be almost negligible, and the calculations therefore provide a good estimate of the ZFS parameters and their solvent dependence based only on the electron spin-spin coupling expectation values. The correlation between the shift in the ZFS and the phosphorescence frequency that has been observed in optically detected magnetic resonance experiments in low-temperature glasses is supported by our direct SSC calculations without taking SOC into account. This makes it possible to distinguish between the two theories that earlier were proposed to explain the inhomogeneous broadening of triplet state spectra, and discard the one that is exclusively based on the SOC-induced mixing of the singlet and triplet states.

  • 39.
    Minaev, Boris
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    Minaeva, Valentina
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    Spin-orbit coupling in dioxygen activation and the role of spin in chemistry2012In: Handbook of Computational Chemistry / [ed] J. Leszczynski, Springer Berlin/Heidelberg, 2012, p. 1067-1093Chapter in book (Refereed)
    Abstract [en]

    We review the general concept of nonadiabatic quantum spin transitions in biochemistry. A few important examples are highlighted to illustrate the concept: the role of spin effects in oxidases, cytochromes, in dioxygen binding to heme, in photosynthesis, and in tentative models of consciousness. The most thoroughly studied of these effects are connected with dioxygen activation by enzymes. Discussion on the mechanisms of overcoming spin prohibitions in dioxygen reactions with flavin-dependent oxygenases and with hemoglobin and myoglobin is presented in some detail. We consider spin-orbit coupling (SOC) between the starting triplet state from the entrance channel of the O2 binding to glucose oxidase, to ferrous heme, and the final singlet open-shell state in these intermediates. Both triplet (T) and singlet (S) states in these examples are dominated by the radical-pair structures D+ -O2− induced by charge transfer; the peculiarities of their orbital configurations are essential for the SOC analysis. An account of specific SOC in the open πg-shell of dioxygen helps to explain the probability of T-S transitions in the active site near the transition state. Simulated potential energy surface cross-sections along the reaction coordinates for these multiplets, calculated by density functional theory, agree with the notion of a relatively strong SOC induced inside the oxygen moiety by an orbital angular momentum change in the πg-shell during the T-S transition. The SOC model explains well the efficient spin inversion during the O2 binding with heme and glucose oxidase, which constitutes a key mechanism for understanding metabolism. Other examples of nontrivial roles of spin effects in biochemistry are briefly discussed.

  • 40.
    Minaev, Boris
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Minaeva, Valentina A.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Evtuhov, Yurij V.
    Quantum-Chemical Study of the Singlet Oxygen Emission2009In: International Journal of Quantum Chemistry, ISSN 0020-7608, E-ISSN 1097-461X, Vol. 109, no 3, p. 500-515Article in journal (Refereed)
    Abstract [en]

    Intensity distribution in rotational lines of the 0-0 band of the a(1)Delta g -> X-3 Sigma(-)(g) transition in the oxygen molecule at lambda = 1270 nm is studied by quadratic response (QR) method in a framework of multiconfiguration self-consisted field (MCSCF) theory. The distance dependence of the transition magnetic moment and the (0-0)/(0-1) bands intensity ratio are calculated. A short review of previous theory of the red and infrared atmospheric oxygen bands and of their enhancement by collisions is presented to analyze and compare the new results. Enhancement of these bands in 0, collisions with Li-2 and N-2 molecules is calculated by QR method. Diamagnetic species simulate solvent molecules of different optical polarizability. Specific influence of collisions on vibronic bands is stressed.

  • 41.
    Minaev, Boris
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Minaeva, Valentina
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Theoretical Study of the Cyclometalated Iridium(III) Complexes Used as Chromophores for Organic Light-Emitting Diodes2009In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 113, no 4, p. 726-735Article in journal (Refereed)
    Abstract [en]

    Time-dependent density functional theory with linear and quadratic response technology is used to calculate electronic structure, spectra, and spin-orbit coupling effects for analysis, of the main mechanism for phosphorescence of the recently synthesized iridium complex [bis(2-phenylpyridine)(2-carboxy-4-dimethyl-aminopyridine)iridium(III)]. This compound exhibits strong green phosphorescence which is used in solution processable organic light-emitting diode devices (OLEDs) to overcome the efficiency limit imposed by the formation of triplet excitons. Attempting to foresee new structure-property relations that can guide an improved design of OLED devices based on phosphorescence of the lowest triplet state, we have conducted a theoretical analysis of the photophysical properties of a series of iridium cyclometalated complexes.

  • 42.
    Minaev, Boris
    et al.
    KTH, Superseded Departments, Biotechnology.
    Tunell, Ingvar
    KTH, Superseded Departments, Biotechnology.
    Salek, Pawel
    KTH, Superseded Departments, Biotechnology.
    Loboda, Oleksandr
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    Vahtras, Olav
    KTH, Superseded Departments, Biotechnology.
    Ågren, Hans
    KTH, Superseded Departments, Biotechnology.
    Singlet-triplet transitions in three-atomic molecules studied by time-dependent MCSCF and density functional theory2004In: Molecular Physics, ISSN 0026-8976, E-ISSN 1362-3028, Vol. 102, no 13, p. 1391-1406Article in journal (Refereed)
    Abstract [en]

    Singlet-triplet transition moments and phosphorescence lifetimes have been calculated for the three-atomic molecules HCN, O-3, H2O, H2S, GeF2, GeCl2 and GeBr2 by time-dependent density functional theory (DFT) utilizing quadratic response functions in order to qualify DFT which recently has become available for studies of this kind [TUNELL, I., RINKEVIVIUS, Z., VAHTRAS, O., SALEK, P., HELGAKER, T., and AGREN, H., 2003, J. chem. phys., 119, 11024]. Comparison with ab initio and experimental data indicates that DFT exhibit results of similar quality as explicitly correlated methods which indicates that it indeed is a viable approach for singlet-triplet transitions. O-3 provides an intriguing example in that a systematic investigation of the singlet-triplet transition moment of its Wulf band indicates a clear advantage of the DFT technique despite the multiconfigurational character of the electronic structure of this molecule. The electronic spin-spin coupling and the hyperfine nuclear coupling constants have also been calculated in order to further characterize the triplet state in the spectra of the investigated systems.

  • 43.
    Minaev, Boris
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Wang, Yanhua
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Wang, Chuankui
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Luo, Yi
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Density functional theory study of vibronic structure of the first absorption Qx band in free-base porphin2006In: Spectrochimica Acta Part A - Molecular and Biomolecular Spectroscopy, ISSN 1386-1425, E-ISSN 1873-3557, Vol. 65, no 2, p. 308-323Article in journal (Refereed)
    Abstract [en]

    Harmonic vibrational frequencies and vibronic intensities in the first S-0 -> S-1 (pi pi*) absorption band of free-base porphin (H2P) are investigated by hybrid density functional theory (DFT) with the standard B3LYP functional. The S-0-S-1 transition probability is calculated using time-dependent DFT with account of Franck-Condon (FC) and Herzberg-Teller (HT) contributions to the electric-dipole transition moments including displacements along all 108 vibrational modes. Two weak wide bands observed in the gas phase absorption spectra of the H2P molecule at 626 and 576 nm are interpreted as the 0-0 band of the X(1)A(g)-> B-3u transition and the 0-1 band with largest contributions from the nu(10)(a(g)) = 1610 cm(-1) and nu(19)(b(1g)) = 1600 cm(-1) modes, respectively, in agreement with previous tentative assignments. Both bands are induced by the HT mechanism, while the FC contributions are negligible. A number of fine structure bands, including combination of two vibrational quanta, are obtained and compared with available spectra from supersonic jet and Shpolskij matrices. Both absorption and fluorescence spectra are interpreted on ground of the linear coupling model and a good fulfillment of the mirror-symmetry rule.

  • 44.
    Minaev, Boris
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    Yaschuk, L.
    Kukueva, V.
    Calculation of the fine structure and intensity of the singlet-triplet transitions in the imidogen radical2005In: Spectrochimica Acta Part A - Molecular and Biomolecular Spectroscopy, ISSN 1386-1425, E-ISSN 1873-3557, Vol. 61, no 6, p. 1105-1112Article in journal (Refereed)
    Abstract [en]

    The singlet-triplet transition moments are calculated for the NH radical by multiconfiguration self-consistent field (MCSCF) method with a quadratic response (QR) technique. The band systems in the visible region (b(l) Sigma(+)-> X-3 Sigma(-) and a(1) Delta -> X-3 Sigma(-)) of the NH radical are analyzed in comparison with previous ab initio treatments and with the recent experimental data in attempt to solve some discrepancies. The b(1)Sigma(+)-> X-3 Sigma(-)(Omega) transition moments ratio for the two spin sublevels Omega = 1 and Omega = 0 of the ground state is well reproduced and the radiative lifetime of the b(1) Sigma(+) state (tau(b) = 58 ms) is obtained in a good agreement with the experimental value tau(b)= 53((+1 7)(-13)) 3[1 3 ms. The A(3) Pi X-3 Sigma-transition some improvement is achieved in comparison with the previous ab initio results, but the calculated radiative lifetime (tau(a) = 3.9 s) is still much lower than the recent measurement provides (tau(a)= 12.5 s). The zero field splitting and spin-rotation coupling constants are calculated for the ground state by different methods and advantage of the density functional theory is stressed.

  • 45.
    Minaev, Boris
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    De Angelis, Filippo
    Theoretical design of phosphorescence parameters for organic electro-luminescence devices based on iridium complexes2009In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 358, no 3, p. 245-257Article in journal (Refereed)
    Abstract [en]

    Tithe-dependent density functional theory with quadratic response methodology is used in order to calculate and compare spin-orbit coupling effects and the main mechanism of phosphorescence of the neutral Ir(ppy)(3) and cationic [Ir(bpy)(3)](3+) tris-iridium compounds, [Ir(ppy)(2)(bpy)](+) and [Ir(2-phenylpyridine)(2)(4,4'-tert-butyl-2,2'-bipyridine](+) complexes, including also the recently synthesised [Ir(2-phenylpyridine)(2)(4,4'-dimethylamino-2,2'-bipyridine](+) and [Ir(2,4-difluorophenylpyridine)(2)(4,4'-dimethylamino-2,2'-bipyridine](+) dyes, where ppy = 2-phenylpyridine and bpy = 2,2'-bipyridine ligands. Comparison with the symmetric, lighter and more studied [Ru(bpy)(3)](2+) and [Rh(bpy)(3)](3+) complexes is also resented. Variations in lifetimes for Ir(ppy)(3) and [Ir(bpy)(3)](3+) dyes as well as for the mixed cationic complexes are well reproduced by the quadratic response method. All the ortho-metalated iridium compounds exhibit strong phosphorescence, which is used in organic light-emitting diodes (OLEDs) to overcome the efficiency limit imposed by the formation of triplet excitons. The results from the first principle theoretical analysis of phosphorescence have helped to clarify the connections between the main features of electronic structure and the photo-physical properties of the studied heavy organometallic OLED materials.

  • 46. Minaeva, V. A.
    et al.
    Minaev, Boris F.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Baryshnikov, G. V.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Pittelkow, M.
    Experimental and theoretical study of IR and Raman spectra of tetraoxa[8]circulenes2012In: Vibrational Spectroscopy, ISSN 0924-2031, E-ISSN 1873-3697, Vol. 61, p. 156-166Article in journal (Refereed)
    Abstract [en]

    The FTIR and Raman spectra of symmetrical derivatives of the tetraoxa[8]circulenes (D 4h symmetry) series have been detected and the experimental data have been interpreted by density functional theory (DFT). The equilibrium molecular geometry, harmonic vibrational frequencies, infrared intensities and Raman scattering activities of the studied tetraoxa[8]circulenes have been calculated by the DFT/B3LYP method with the 6-31G(d) basis set using the symmetry constrains. Comparison of the calculated vibrational spectra with the experimental data provides reliable assignments of all observed bands in FTIR and Raman spectra, including the low frequency region. Correlation diagrams with symmetry account of vibrational modes in the studied molecules and their constituents (benzene, naphthalene and furan) have been used and proven very useful in the force field and frequency analysis. The results of quantum-chemical calculations are in excellent agreement with all details of the experimental spectra.

  • 47. Minaeva, V. A.
    et al.
    Minaev, Boris F.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Baryshnikov, Gleb V.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Calculation of the optical spectra of the copper(I) complex with triphenylphosphine, iodine, and 3-pyridine-2-yl-5-phenyl-1H-1,2,4-triazole by the DFT method2017In: Optics and Spectroscopy, ISSN 0030-400X, E-ISSN 1562-6911, Vol. 122, no 2, p. 175-183Article in journal (Refereed)
    Abstract [en]

    The IR and UV spectra of the [CuIL(PPh3)] complex (PPh3 = triphenylphosphine, L = 3-pyridine- 2-yl-5-phenyl-1De-1,2,4-triazole) have been analyzed in detail within the density functional theory (DFT) and its time-dependent version TD DFT. The standard functional B3LYP and sets of basis orbitals 6-311G(d,p) and Lanl2DZ are used for the atoms of the elements of periods I and II and for the iodine atom, respectively. The calculated IR spectra of the complex and free ligands coincide with the observed IR bands, due to which one can completely interpret all normal modes and confirm X-ray diffraction (XRD) data. Particular attention is paid to the structure of excited triplet (D cent (1)) state in order to explain the role of copper and iodine ions in the formation of photo- and electroluminescence spectra. It is shown that the equilibrium D cent (1) state undergoes structural relaxation after the vertical excitation and significantly changes its electronic nature and the charge transfer structure.

  • 48. Minaeva, Valentina A.
    et al.
    Minaev, Boris F.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Baryshnikov, Gleb V.
    Romeyko, Olga M.
    Pittelkow, Michael
    The FTIR spectra of substituted tetraoxa[8]circulenes and their assignments based on DFT calculations2013In: Vibrational Spectroscopy, ISSN 0924-2031, E-ISSN 1873-3697, Vol. 65, p. 147-158Article in journal (Refereed)
    Abstract [en]

    The FTIR spectrum of symmetrical derivative of the tetraoxa[8]circulene, named para-dinaphthyleno-2,3,10,11-tetraundecyldiphenylenotetrafuran (p-2B2N4R, R = n-C11H23) has been recorded and interpreted using density functional theory (DFT) calculations for the model compounds p-2B2N4R (R = H, C2H5). The unsubstituted tetraoxa[8]circulene, namely para-dinaphthylenodiphenylenotetrafuran (p2B2N) and para-dinaphthyleno-2,3,10,11-tetraethyldiphenylenotetrafuran (p-2B2N4R, R = C2H5) belong to the D-2h and D-2 symmetry point groups, respectively. The equilibrium molecular geometry, harmonic vibrational frequencies and infrared intensities have been calculated utilizing the DFT/B3LYP method with the 6-31G(d) basis set using the symmetry constraints. Comparison of the calculated vibrational spectra with the experimental data provides a reliable assignment of the observed bands in the FTIR spectra. The results of quantum-chemical calculations provide a complete interpretation of vibrational modes based on a good agreement with all details of the experimental spectra.

  • 49.
    Mohammed, Abdelsalam
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    Minaev, Boris
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    Lindgren, Mikael
    Norman, Patrick
    Classification of Raman active modes of platinum(II) acetylides: A combined experimental and theoretical study2009In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 481, no 4-6, p. 209-213Article in journal (Refereed)
    Abstract [en]

    Non-resonance Raman scattering of platinum(II) acetylide molecules is studied both by theory and experiment. Differential cross sections are presented for bis((4-(phenyl-ethynyl)phenyl)ethynyl)bis(tri-n-butylphosphine)platinum( II) (Pt1), and for bis((4-(phenyl-ethynyl) bis(tri-n-butylphosphine) platinum(II) substituted with triazole end group (Z1). All intense bands in the observed Raman scattering are assigned to symmetric vibrations of Pt-C C, C C, and phenyl groups; a reliable interpretation includes some details of relative intensities for the stretching and in-plane bending modes. The Raman spectra verify that the Pt-acetylide dyes remain intact during the material processing, indicating that they retain functionality for applications like in optical power limiting, nonlinear optics, and light emitting diodes.

  • 50. Oprea, Corneliu I.
    et al.
    Frecus, Bogdan
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Minaev, Boris F.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Girtu, Mihai A.
    DFT study of electronic structure and optical properties of some Ru- and Rh-based complexes for dye-sensitized solar cells2011In: Molecular Physics, ISSN 0026-8976, E-ISSN 1362-3028, Vol. 109, no 21, p. 2511-2523Article in journal (Refereed)
    Abstract [en]

    The paper reports Time Dependent Density Functional Theory (TD DFT) calculations providing the structure, electronic properties and spectra of [Ru(II)(bpy)(3-n)(dcbpy)(n)](2+) and [Rh(III)(bpy)(3-n)(dcbpy)(n)](3+) complexes, where bpy = 2,2'-bipyridyl, dcbpy = 4,4'-dicarboxy-2,2'-bipyridyl, and n = 0, 1, 2, 3, studied as possible pigments for dye-sensitized solar cells. The role of the metallic ion and of the COOH groups on the optical properties of these complexes are compared and contrasted and their relevance as dyes for hybrid organic-inorganic photovoltaic cells is discussed. It was found that the optical spectra are strongly influenced by the metallic ion, with visible absorption bands for the Ru(II) complexes and only ultraviolet bands for the Rh(III) complexes. Upon excitation, the extra positive charge of the Rh(3+) centre tends to draw electrons towards the metal ion, facilitating some charge transfer from the ligand to the metal, whereas in the case of the Ru(2+) ion the electron transfer is clearly from the metal to the ligand. The carboxyl groups play an important role in strengthening the absorption bands in solution in the visible region. Of the complexes studied, the most suited as pigments for dye-sensitized solar cells are the [Ru(II)(bpy)(3-n)(dcbpy)(n)](2+) complexes with n = 1 and 2. This is based on the following arguments: (i) their intense absorption band in the visible region, (ii) the presence of the anchoring groups allowing the bonding to the TiO(2) substrate and the charge transfer, and (iii) the good energy level alignment with the conduction band edge of the semiconducting substrate and the redox level of the electrolyte.

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