109 results on '"Rashid R, Valiev"'
Search Results
2. Site Selective Concerted Nucleophilic Aromatic Substitutions of Azole‐Ligated Diaryliodonium Salts
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Yulia A. Vlasenko, Thomas J. Kuczmera, Nikita S. Antonkin, Rashid R. Valiev, Pavel S. Postnikov, and Boris J. Nachtsheim
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General Chemistry - Published
- 2023
3. Gold(<scp>i</scp>)-containing light-emitting molecules with an inverted singlet–triplet gap
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Daniel Blasco, Rinat T. Nasibullin, Rashid R. Valiev, and Dage Sundholm
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General Chemistry - Abstract
Substitution with gold(i)-containing moieties results in non-vanishing oscillator strengths and spin–orbit coupling leading to fast intersystem crossing in light-emitting heptazine derivates with an inverted singlet–triplet gap.
- Published
- 2023
4. Photo- and Electroluminescent Neutral Iridium(III) Complexes Bearing Imidoylamidinate Ligands
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Eugene A. Katlenok, Anton V. Rozhkov, Ruslan R. Ramazanov, Rashid R. Valiev, Oleg V. Levin, Dmitrii O. Goryachiy, Ilya V. Taydakov, Maxim L. Kuznetsov, and Vadim Yu Kukushkin
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Inorganic Chemistry ,Physical and Theoretical Chemistry - Abstract
Imidoylamidinate-based heteroleptic bis(2-phenylbenzothiazole)iridium(III) and -rhodium(III) complexes [(
- Published
- 2022
5. Non-intersecting ring currents in [12]infinitene
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Mesías Orozco-Ic, Rashid R. Valiev, and Dage Sundholm
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General Physics and Astronomy ,Physical and Theoretical Chemistry - Abstract
The aromaticity of the newly synthesized [12]infinitene is addressed via analysis of the magnetically induced current density and the induced magnetic field. Our calculations reveal that [12]infinitene responds to an external magnetic field by creating two current-density pathways that flow diatropically along the edges of the molecule. The current-density pathways do not intersect. The entire structure is completely shielded suggesting that the infinitene molecule is aromatic, contrary to what the Möbius rule for twisted annulene structures predicts. We also studied the dication of [12]infinitene, which sustains two paratropic ring currents flowing along the edges. The space between the stacked rings at the crossing point is shorter for the dication as compared to the neutral molecule. Hence, a strong through-space current density appears at the crossing point of π-π stacked rings.
- Published
- 2022
6. Integration of global ring currents using the Ampère–Maxwell law
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Raphael J. F. Berger, Maria Dimitrova, Rinat T. Nasibullin, Rashid R. Valiev, Dage Sundholm, Department of Chemistry, INAR Physical Chemistry, and Doctoral Programme in Chemistry and Molecular Sciences
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ANISOTROPY ,NICS ,010304 chemical physics ,INDEPENDENT CHEMICAL-SHIFTS ,010405 organic chemistry ,116 Chemical sciences ,General Physics and Astronomy ,01 natural sciences ,INDUCED CURRENT DENSITIES ,0104 chemical sciences ,кольцевой ток ,Ампера-Максвелла закон ,0103 physical sciences ,Physical and Theoretical Chemistry ,AROMATICITY ,SIGMA ,INDUCED MAGNETIC-FIELD - Abstract
Magnetically induced ring currents are calculated from the magnetic shielding tensor by employing the Ampere-Maxwell law. The feasibility of the method is demonstrated by integrating the zz component of the shielding tensor along the symmetry axis of highly symmetric ring-shaped aromatic, antiaromatic and nonaromatic molecules. The calculated ring-current strengths agree perfectly with the ones obtained by integrating the current-density flux passing through a plane cutting half the molecular ring. The method can be used in combination with all electronic structure codes capable of calculating nuclear magnetic resonance (NMR) shielding tensors in general points in space. We also show that nucleus independent chemical shifts (NICS) along the symmetry axis are related to the spatial derivative of the strength of the global ring-current along the z axis.
- Published
- 2022
7. On the origin of the inverted singlet-triplet gap of the 5th generation light-emitting molecules
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Lucie Tučková, Michal Straka, Rashid R. Valiev, and Dage Sundholm
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General Physics and Astronomy ,Physical and Theoretical Chemistry - Abstract
Excitation energies of the lowest singlet and triplet state of molecules whose first excited singlet state lies energetically below the first triplet state have been studied computationally at (time-dependent) density functional theory, coupled-cluster, and second-order multiconfiguration perturbation theory levels. The calculations at the
- Published
- 2022
8. Odd-Number Cyclo[
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Glib V, Baryshnikov, Rashid R, Valiev, Lenara I, Valiulina, Alexandr E, Kurtsevich, Theo, Kurtén, Dage, Sundholm, Michael, Pittelkow, Jinglai, Zhang, and Hans, Ågren
- Abstract
Cyclo[
- Published
- 2022
9. Fast estimation of the internal conversion rate constant in photophysical applications
- Author
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Rashid R. Valiev, A. E. Kurtsevich, Rinat T. Nasibullin, Dage Sundholm, Victor N. Cherepanov, Theo Kurtén, and Department of Chemistry
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Materials science ,116 Chemical sciences ,General Physics and Astronomy ,02 engineering and technology ,010402 general chemistry ,перенос энергии ,7. Clean energy ,01 natural sciences ,Molecular physics ,электронное возбуждение ,chemistry.chemical_compound ,Reaction rate constant ,Molecule ,Physics::Chemical Physics ,Physical and Theoretical Chemistry ,Azulene ,021001 nanoscience & nanotechnology ,Internal conversion (chemistry) ,электронная волновая функция ,Acceptor ,0104 chemical sciences ,Fluorenone ,chemistry ,Solvent effects ,0210 nano-technology ,Excitation - Abstract
An efficient method for estimating non-adiabatic coupling matrix elements (NACME) and rate constants for internal conversion (k(IC)) is presented. The method, based on Plotnikov's theory, requires only calculations of the electronic wave functions and the corresponding electronic excitation energies. Computationally expensive calculations of the derivatives of the electronic wave function with respect to the nuclear coordinates are avoided. When the main accepting modes of the electronic excitation energy are X-H vibrations, the present method can be used for estimating the efficiency of the energy transfer between donor and acceptor molecules. It can also be used in studies of the influence of hydrogen bonding or solvent effect on fluorescence quenching, in studies of vibronic effects of TADF (thermally activated delayed fluorescence) emitters, and for calculating k(IC). Here, k(IC) and NACME are calculated for free-base porhyrin, magnesium porphyrin, azulene, naphthalene, pyrene and fluorenone interacting with a solvent molecule. Reverse k(IC) and NACME are further calculated for the T-1 -> T-2 transition of dibenzothiophene-S,S-dioxide (PTZ-DBTO2), which is used in TADF applications. Finally, we estimate the efficiency of the energy transfer between two large porphyrinoid dimers.
- Published
- 2021
10. Magnetically induced ring currents in metallocenothiaporphyrins
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Rashid R. Valiev, Theo Kurten, Lenara I. Valiulina, Sergey Yu. Ketkov, Viktor N. Cherepanov, Maria Dimitrova, Dage Sundholm, INAR Physical Chemistry, Department of Chemistry, and Department of Physics
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ароматичность ,010405 organic chemistry ,QUANTUM CONTRIBUTIONS ,PHOTOCHEMISTRY ,электронные состояния ,116 Chemical sciences ,METALLOCENE COMPOUNDS ,металлоценотиапорфирины ,General Physics and Astronomy ,010402 general chemistry ,01 natural sciences ,STATE ,0104 chemical sciences ,EXPANDED PORPHYRINS ,кольцевой ток ,CURRENT DENSITIES ,CHEMISTRY ,PHOTOPHYSICAL PROPERTIES ,Physical and Theoretical Chemistry ,AROMATICITY - Abstract
The magnetically induced current-density susceptibility tensor (CDT) of the lowest singlet and triplet states of the metallocenothiaporphyrins, where the metal is V, Cr, Mn, Fe, Co, Ni, Mo, Tc, Ru, or Rh, have been studied with the gauge-including magnetically induced currents (GIMIC) method. The compounds containing V, Mn, Co, Tc or Rh were studied as cations because the neutral molecules have an odd number of electrons. The calculations show that the aromatic nature of most of the studied molecules follows the Huckel and Baird rules of aromaticity. CDT calculations on the high-spin states of the neutral metallocenothiaporphyrins with V, Mn, Co, Tc or Rh also shows that these molecules follow a unified extended Huckel and Baird aromaticity orbital-count rule stating that molecules with an odd number of occupied conjugated valence orbitals are aromatic, whereas molecules with an even number of occupied conjugated orbitals are antiaromatic.
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- 2022
11. Odd-Number Cyclo[n]Carbons Sustaining Alternating Aromaticity
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Glib V. Baryshnikov, Rashid R. Valiev, Lenara I. Valiulina, Alexandr E. Kurtsevich, Theo Kurtén, Dage Sundholm, Michael Pittelkow, Jinglai Zhang, and Hans Ågren
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электронная структура ,ароматичность ,CARBON CLUSTERS ,DENSITY FUNCTIONALS ,теория функционала плотности ,THERMOCHEMISTRY ,MOLECULAR-ORBITAL METHODS ,ELECTRONIC-STRUCTURE ,DESIGN ,Teoretisk kemi ,ALL-CARBOATOMIC RING ,Physical and Theoretical Chemistry ,Theoretical Chemistry ,циклоуглероды ,TRANSITION ,BASIS-SETS ,GENERATION - Abstract
Cyclo[n]carbons (n = 5, 7, 9,..., 29) composed from an odd number of carbon atoms are studied computationally at density functional theory (DFT) and ab initio complete active space self-consistent field (CASSCF) levels of theory to get insight into their electronic structure and aromaticity. DFT calculations predict a strongly delocalized carbene structure of the cyclo[n]carbons and an aromatic character for all of them. In contrast, calculations at the CASSCF level yield geometrically bent and electronically localized carbene structures leading to an alternating double aromaticity of the odd-number cyclo[n]carbons. CASSCF calculations yield a singlet electronic ground state for the studied cyclo[n]carbons except for C25, whereas at the DFT level the energy difference between the lowest singlet and triplet states depends on the employed functional. The BHandHLYP functional predicts a triplet ground state of the larger odd-number cyclo[n]carbons starting from n = 13. Current-density calculations at the BHandHLYP level using the CASSCFoptimized molecular structures show that there is a through-space delocalization in the cyclo[n]carbons. The current density avoids the carbene carbon atom, leading to an alternating double aromaticity of the oddnumber cyclo[n]carbons satisfying the antiaromatic [4k+1] and aromatic [4k+3] rules. C11, C15, and C19 are aromatic and can be prioritized in future synthesis. We predict a bond-shift phenomenon for the triplet state of the cyclo[n]carbons leading to resonance structures that have different reactivity toward dimerization. Funding Agencies|Swedish Research Council [2020-04600]; Academy of Finland [325369, 314821]; Danish Council for Independent Research [DFF4181-00206, 9040-00265]; VILLUM FONDEN [40871]; Russian Scientific Foundation [18-19-00268-Pi]
- Published
- 2022
12. Application of a 2D Molybdenum Telluride in SERS Detection of Biorelevant Molecules
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Oleksiy Lyutakov, Zdenka Kolska, Rashid R. Valiev, Olga Guselnikova, Pavel S. Postnikov, Alexey Y. Ganin, Elena Miliutina, James P. Fraser, Václav Švorčík, and Department of Chemistry
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chemical enhancement ,Materials science ,Surface Properties ,116 Chemical sciences ,215 Chemical engineering ,MoTe2 ,EFFICIENT ,Nanotechnology ,02 engineering and technology ,Spectrum Analysis, Raman ,FILMS ,010402 general chemistry ,01 natural sciences ,Metal ,symbols.namesake ,CHARGE-TRANSFER ,Molecule ,General Materials Science ,Particle Size ,beta-sitosterol ,Density Functional Theory ,sensing ,Molybdenum ,SERS ,PLATFORM ,021001 nanoscience & nanotechnology ,Sitosterols ,0104 chemical sciences ,Molybdenum telluride ,LAYER ,visual_art ,symbols ,visual_art.visual_art_medium ,ENHANCED RAMAN-SCATTERING ,Tellurium ,0210 nano-technology ,Raman spectroscopy - Abstract
Two-dimensional (2D) transition-metal dichalcogenides have become promising candidates for surface-enhanced Raman spectroscopy (SERS), but currently very few examples of detection of relevant molecules are available. Herein, we show the detection of the lipophilic disease marker beta-sitosterol on few-layered MoTe2 films. The chemical vapor deposition (CVD)-grown films are capable of nanomolar detection, exceeding the performance of alternative noble-metal surfaces. We confirm that the enhancement occurs through the chemical enhancement (CE) mechanism via formation of a surface-analyte complex, which leads to an enhancement factor of approximate to 10(4), as confirmed by Fourier transform infrared (FTIR), UV-vis, and cyclic voltammetry (CV) analyses and density functional theory (DFT) calculations. Low values of signal deviation over a seven-layered MoTe2 film confirms the homogeneity and reproducibility of the results in comparison to noble-metal substrate analogues. Furthermore, beta-sitosterol detection within cell culture media, a minimal loss of signal over 50 days, and the opportunity for sensor regeneration suggest that MoTe2 can become a promising new SERS platform for biosensing.
- Published
- 2020
13. When are Antiaromatic Molecules Paramagnetic?
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Glib V. Baryshnikov, Hans Ågren, Rashid R. Valiev, Rinat T. Nasibullin, Dage Sundholm, and Department of Chemistry
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NICS ,Materials science ,116 Chemical sciences ,VALENCE ,RING CURRENTS ,02 engineering and technology ,PLANAR ,010402 general chemistry ,01 natural sciences ,DIAMAGNETIC SUSCEPTIBILITY ,chemistry.chemical_compound ,Paramagnetism ,MAGNETIC-PROPERTIES ,MAGNETIZABILITIES ,Molecule ,CH+ ,Physical and Theoretical Chemistry ,AROMATICITY ,Valence (chemistry) ,Aromaticity ,021001 nanoscience & nanotechnology ,Porphyrin ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Crystallography ,General Energy ,chemistry ,PORPHYRIN TAPES ,0210 nano-technology ,Antiaromaticity - Abstract
Magnetizabilities and magnetically induced current densities have been calculated and analyzed for a series of antiaromatic cyclo[4k]carbons (k = 2-11), iso[n]phlorins (n = 4-8), expanded porphyrinoids, and meso-meso, beta-beta,beta-beta triple-linked porphyrin and isophlorin arrays. The cyclo[4k]carbons with k = 2-6 are predicted to be closed-shell paramagnetic molecules due to the very strong paratropic ring current combined with its large radius. Larger cyclo[4k]carbons with k = 6-11 are diamagnetic because they sustain a paratropic ring current whose strength is weaker than -20 nA T-1, which seems to be the lower threshold value for closed-shell paramagnetism. This holds not only for cyclo[4k]carbons but also for other organic molecules like expanded porphyrinoids and oligomers of porphyrinoids. The present study shows that meso-meso, beta-beta, beta-beta triple-linked linear porphyrin and isophlorin arrays have a domainlike distribution of alternating diatropic and paratropic ring currents. The strength of their local paratropic ring currents is weaker than -20 nA T-1 in each domain. Therefore, linear porphyrin and isophlorin arrays become more diamagnetic with increasing length of the ribbon. For the same reason, square-shaped meso-meso, beta-beta, beta-beta triple-linked free-base porphyrin and isophlorin tetramers as well as the Zn(II) complex of the porphyrin tetramer are diamagnetic. We show that closed-shell molecules with large positive magnetizabilities can be designed by following the principle that a strong paratropic current ring combined with a large ring-current radius leads to closed-shell paramagnetism.
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- 2020
14. Theoretical Study of Nonradiative Energy Transfer from Exciplex to Perovskites
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Rinat T. Nasibullin, Rashid R. Valiev, Gleb V. Baryshnikov, Yu. V. Konyshev, and Victor N. Cherepanov
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Materials science ,Chemical physics ,Energy transfer ,OLED ,General Physics and Astronomy ,Molecule ,Excimer ,Fluorescence ,Perovskite (structure) - Abstract
The results of theoretical studies of energy transfer from the exciplex of TCTA and Bphen molecules to CaZrO3, SrZrO3, and BaZrO3 perovskites are presented. As a result, the molecular structure of TCTA/Bphen exciplex is determined. A computational scheme is proposed that allows the efficiencies of energy transfer from the exciplex to perovskites to be compared qualitatively.
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- 2020
15. Photophysical properties of the triangular [Au(HNCOH)]3 complex and its dimer
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Rashid R. Valiev, Dage Sundholm, and Jonas Greiner
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Materials science ,Dimer ,Relaxation (NMR) ,General Physics and Astronomy ,Quantum yield ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Internal conversion (chemistry) ,01 natural sciences ,7. Clean energy ,Molecular physics ,0104 chemical sciences ,chemistry.chemical_compound ,Intersystem crossing ,chemistry ,Physical and Theoretical Chemistry ,Perturbation theory ,Triplet state ,0210 nano-technology ,Phosphorescence - Abstract
Rate constants for radiative and non-radiative transitions of the [Au(HNCOH)]3 complex and its dimer were calculated within the Herzberg–Teller approximation based on quantum mechanical principles. A high triplet quantum yield was estimated for the monomer. Internal conversion (IC) was found to be the major competing process to the intersystem crossing (ISC) from the lowest excited singlet state (S1) to the lowest triplet state (T1). ISC and IC from the spin-mixed 1 state also dominate the triplet relaxation process resulting in a negligible phosphorescence quantum yield for the monomer. The IC and ISC rate constants of the dimer are considerably smaller due to much lower Franck–Condon factors. For the dimer a triplet quantum yield of 0.71 was estimated using the extended multi-configuration quasi-degenerate second-order perturbation theory (XMCQDPT2) method to calculate the transition energies. Fluorescence is the major competing process to the ISC relaxation of the S1 state of the dimer. The ISC and IC processes are insignificant for the relaxation of the T1 state, resulting in unity phosphorescence quantum yield. The high triplet and phosphorescence quantum yields of the [Au(HNCOH)]3 dimer make it and its higher oligomers potential candidates as dopants for phosphorescent organic light emitting diodes and as down-converters in solid-state lighting systems.
- Published
- 2020
16. Cyclo[18]carbon: Insight into Electronic Structure, Aromaticity, and Surface Coupling
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Dage Sundholm, Glib V. Baryshnikov, Hans Ågren, Rashid R. Valiev, Artem V. Kuklin, and Department of Chemistry
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GRAPHENE ,Materials science ,VIBRATIONAL FREQUENCIES ,116 Chemical sciences ,Ab initio ,chemistry.chemical_element ,02 engineering and technology ,Electronic structure ,C-18 ,010402 general chemistry ,01 natural sciences ,law.invention ,chemistry.chemical_compound ,law ,Computational chemistry ,Physics::Atomic and Molecular Clusters ,Theoretical chemistry ,SPECTRA ,General Materials Science ,Physics::Chemical Physics ,CUMULENE ,Physical and Theoretical Chemistry ,CARBON MOLECULES ,Graphene ,Cumulene ,Aromaticity ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,chemistry ,Density functional theory ,0210 nano-technology ,Carbon - Abstract
Cyclo[18]carbon (C18) is studied computationally at density functional theory (DFT) and ab initio levels to obtain insights into its electronic structure, aromaticity, and adsorption properties on the NaCl surface. DFT functionals with a small amount of Hartree-Fock exchange as well as XMC-QDPT2 calculations fail to determine the experimentally observed polyyne molecular structure revealing a cumulene-type geometry. Exchange-correlation functionals with a large amount of Hartree-Fock ex-change as well as ab initio CASSCF calculations yield the polyyne structure is a ground state while the cumulene structure corresponds to the transition state between the two inverted polyyne structures through the Kekule distortion. The polyyne and the cumulene structures are found to be doubly Hückel aromatic. The calculated adsorption energy of cyclo[18]carbon on the NaCl surface is small (37 meV/C) and almost the same for both structures implying that the surface does not stabilize a particular geometry.
- Published
- 2019
17. Computational Investigation of the Formation of Peroxide (ROOR) Accretion Products in the OH- and NO3-Initiated Oxidation of alpha-Pinene
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Galib Hasan, Rashid R. Valiev, Vili-Taneli Salo, Theo Kurtén, INAR Physical Chemistry, Doctoral Programme in Chemistry and Molecular Sciences, Department of Chemistry, Doctoral Programme in Materials Research and Nanosciences, Doctoral Programme in Atmospheric Sciences, and Department of Physics
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MECHANISM ,010504 meteorology & atmospheric sciences ,INITIATED OXIDATION ,116 Chemical sciences ,NOX ,010402 general chemistry ,01 natural sciences ,NITRATES ,0104 chemical sciences ,MODEL ,CHEMISTRY ,SECONDARY ORGANIC AEROSOL ,RADICALS ,Physical and Theoretical Chemistry ,HYDROCARBONS ,0105 earth and related environmental sciences - Abstract
The formation of accretion products ("dimers") from recombination reactions of peroxyl radicals (RO2) is a key 5 3 step in the gas-phase generation of low-volatility vapors, leading to atmospheric aerosol particles. We have recently demonstrated that S 1 this recombination reaction very likely proceeds via an intermediate complex of two alkoxy radicals (RO center dot center dot center dot OR') and that the accretion product pathway involves an intersystem crossing (ISC) of this complex from the triplet to the singlet surface. However, ISC rates have hitherto not been computed for large and chemically complex RO center dot center dot center dot OR' systems actually relevant to atmospheric aerosol formation. Here, we carry out systematic conformational sampling and ISC rate calculations on (3)(RO center dot center dot center dot OR') clusters formed in the recombination reactions of different diastereomers of the first-generation peroxyl radicals originating in both OH- and NO3 -initiated reactions of alpha-pinene, a key biogenic hydrocarbon for atmospheric aerosol formation. While we find large differences between the ISC rates of different diastereomer pairs, all systems have ISC rates of at least 10(6) s(-1), and many have rates exceeding 10(10) s(-1). Especially the latter value demonstrates that accretion product formation via the suggested pathway is a competitive process also for alpha-pinene-derived RO2 and likely explains the experimentally observed gas-phase formation of C-20 compounds in alpha-pinene oxidation.
- Published
- 2021
18. Computational Investigation of the Formation of Peroxide (ROOR) Accretion Products in the OH- and NO
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Galib, Hasan, Rashid R, Valiev, Vili-Taneli, Salo, and Theo, Kurtén
- Subjects
Article - Abstract
The formation of accretion products (“dimers”) from recombination reactions of peroxyl radicals (RO2) is a key step in the gas-phase generation of low-volatility vapors, leading to atmospheric aerosol particles. We have recently demonstrated that this recombination reaction very likely proceeds via an intermediate complex of two alkoxy radicals (RO···OR′) and that the accretion product pathway involves an intersystem crossing (ISC) of this complex from the triplet to the singlet surface. However, ISC rates have hitherto not been computed for large and chemically complex RO···OR′ systems actually relevant to atmospheric aerosol formation. Here, we carry out systematic conformational sampling and ISC rate calculations on 3(RO···OR′) clusters formed in the recombination reactions of different diastereomers of the first-generation peroxyl radicals originating in both OH- and NO3-initiated reactions of α-pinene, a key biogenic hydrocarbon for atmospheric aerosol formation. While we find large differences between the ISC rates of different diastereomer pairs, all systems have ISC rates of at least 106 s–1, and many have rates exceeding 1010 s–1. Especially the latter value demonstrates that accretion product formation via the suggested pathway is a competitive process also for α-pinene-derived RO2 and likely explains the experimentally observed gas-phase formation of C20 compounds in α-pinene oxidation.
- Published
- 2021
19. Unveiling the role of chemical and electronic structure in plasmon-assisted homolysis of alkoxyamines
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Elena Miliutina, Pavel S. Postnikov, Olga Guselnikova, Rashid R. Valiev, Václav Švorčík, Oleksiy Lyutakov, Sylvain R. A. Marque, Gérard Audran, Darya E. Votkina, Jean-Patrick Joly, Lenara I. Valiulina, Jeffrey Havot, Andrii Trelin, and Pavel V. Petunin
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Reaction rate constant ,Chemistry ,law ,Intramolecular force ,Electronic structure ,Surface plasmon resonance ,Photochemistry ,Electron paramagnetic resonance ,Chemical reaction ,Plasmon ,Homolysis ,law.invention - Abstract
The excitation of localized plasmon resonance on nanoparticles followed by the interaction with organic molecules leads to new pathways of chemical reactions. Although a number of physical factors (temperature, illumination regime, type of nanoparticles, etc.) are affecting this process, the role of the chemical factors is underestimated. Challenging this assumption, here we studied the kinetic of plasmon-induced homolysis of five alkoxyamines (AAs) with different chemical and electronic structures using electron paramagnetic resonance (EPR). The kinetic data revealed the dependence of plasmonic homolysis rate constant (kd) with the HOMO energy of AAs, which cannot be described by the kinetic parameters derived from thermal homolysis experiments. The observed trend in kd allowed to suggest the key role of intramolecular excitation mechanism supported by the TDFDT calculations, additional spectroscopic characterization, and control experiments. Our work sheds light on the role of the electronic structure of organic molecules in plasmonic chemistry.
- Published
- 2021
20. Positional Isomers of Isocyanoazulenes as Axial Ligands Coordinated to Ruthenium(II) Tetraphenylporphyrin: Fine-Tuning Redox and Optical Profiles
- Author
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Rashid R. Valiev, Mason D. Hart, Victor N. Nemykin, Mahtab Fathi-Rasekh, Yuriy V. Zatsikha, Toshinori Nakakita, Mikhail V. Barybin, Gregory T. Rohde, and Department of Chemistry
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116 Chemical sciences ,DENSITY FUNCTIONALS ,chemistry.chemical_element ,010402 general chemistry ,01 natural sciences ,Redox ,Inorganic Chemistry ,chemistry.chemical_compound ,лиганды ,позиционные изомеры ,Tetraphenylporphyrin ,Structural isomer ,Physical and Theoretical Chemistry ,тетрафенилпорфирин ,BASIS-SETS ,рутений ,010405 organic chemistry ,Chemistry ,LOW-SPIN ,0104 chemical sciences ,Ruthenium ,ELECTRONIC-STRUCTURE ,Crystallography ,MAGNETIC CIRCULAR-DICHROISM ,IRON(II) PHTHALOCYANINE ,GROUND-STATE ,PORPHYRIN ,COMPLEXES ,ISOCYANIDE - Abstract
Two isomeric ruthenium(II)/5,10,15,20-tetraphe-nylporphyrin complexes featuring axially coordinated redox-active, low-optical gap 2- or 6-isocyanoazulene ligands have been isolated and characterized by NMR, UV-vis, and magnetic circular dichroism (MCD) spectroscopic methods, high-resolution mass spectrometry, and single-crystal X-ray crystallography. The UV-vis and MCD spectra support the presence of the low-energy, azulene-centered transitions in the Q band region of the porphyrin chromophore. The first coordination sphere in new L2RuTPP complexes reflects compressed tetragonal geometry. The redox properties of the new compounds were assessed by electrochemical and spectroelectrochemical means and correlated with the electronic structures predicted by density functional theory and CASSCF calculations. Both experimental and theoretical data are consistent with the first two reduction processes involving the axial azulenic ligands, whereas the oxidation profile (in the direction of increasing potential) is exerted by the ruthenium ion, the porphyrin core, and the axial azulenic moieties.
- Published
- 2019
21. Electroluminescence of a Zinc Complex Exciplex with a Hole-Transporting Material
- Author
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Rashid R. Valiev, Konstantin M. Degtyarenko, Yu. V. Konyshev, A. V. Odod, I. K. Yakushchenko, Ruslan M. Gadirov, S. S. Krasnikova, and T. N. Kopylova
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010302 applied physics ,эксиплексы ,Materials science ,010308 nuclear & particles physics ,флуоресценция ,General Physics and Astronomy ,chemistry.chemical_element ,Zinc ,Electroluminescence ,электролюминесценция ,Photochemistry ,Excimer ,01 natural sciences ,chemistry ,Excited state ,0103 physical sciences ,OLED ,Molecule ,Ground state ,органические светодиоды ,Layer (electronics) - Abstract
Results of theoretical and experimental studies of exciplex of a zinc complex Zn(DFP-SAMQ)2 with the hole-transporting layer of NPD are presented. It is shown that at least three different arrangements of Zn(DFP-SAMQ)2 and NPD molecules in the excited state result in the long-wavelength charge-transfer emission bands. At the same time, such systems are unstable in the ground state.
- Published
- 2019
22. Photophysical Constants of the Tetraoxa[8]Circulene Molecule
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Rashid R. Valiev, Gleb V. Baryshnikov, Victor N. Cherepanov, and Yu. V. Konyshev
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010302 applied physics ,Physics ,010308 nuclear & particles physics ,Degenerate energy levels ,Circulene ,General Physics and Astronomy ,Quantum yield ,Time-dependent density functional theory ,Internal conversion (chemistry) ,01 natural sciences ,Molecular physics ,Reaction rate constant ,Excited state ,0103 physical sciences ,Singlet state - Abstract
The rate constants of photophysical processes (radiation rate constant, internal conversion rate constant, and quantum fluorescence yield) have been calculated for the tetraoxa[8]circulene molecule by the INDO/S, TDDFT, and CC2 methods. It is confirmed that the doubly degenerate triplet level Т2 and the level Т1 are located below the first singlet excited level S1. According to the selection rules for the angular momentum, the spin-orbit interaction between the levels S1 and T1 (S1 and T2) is equal to zero. Therefore, the internal conversion is the only nonradiative channel in this molecule. The results of calculations also demonstrate that values of the internal conversion rate constant and the quantum fluorescence yield obtained by the INDO/S method are incorrect.
- Published
- 2019
23. 2-Iodoxybenzoic acid ditriflate: the most powerful hypervalent iodine(<scp>v</scp>) oxidant
- Author
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Rashid R. Valiev, Mekhman S. Yusubov, Pavel S. Postnikov, Natalia S. Soldatova, Akira Yoshimura, Thomas Wirth, Viktor V. Zhdankin, and Victor N. Nemykin
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гипервалентный йод ,010405 organic chemistry ,Chemistry ,Oxidation resistant ,Metals and Alloys ,Hypervalent molecule ,chemistry.chemical_element ,General Chemistry ,010402 general chemistry ,Iodine ,рентгеновская кристаллография ,01 natural sciences ,Combinatorial chemistry ,Catalysis ,0104 chemical sciences ,3. Good health ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry.chemical_compound ,2-йодоксибензойная кислота ,2-Iodoxybenzoic acid ,Materials Chemistry ,Ceramics and Composites ,Single crystal - Abstract
A ditriflate derivative of 2-iodoxybenzoic acid (IBX) was prepared by the reaction of IBX with trifluoromethanesulfonic acid and characterized by single crystal X-ray crystallography. IBX-ditriflate is the most powerful oxidant in a series of structurally similar IBX derivatives which is best illustrated by its ability to readily oxidize hydrocarbons and the oxidation resistant polyfluoroalcohols.
- Published
- 2019
24. Aromaticity and photophysics of tetrasila- and tetragerma-annelated tetrathienylenes as new representatives of the hetero[8]circulene family
- Author
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Victor N. Cherepanov, Nataliya N. Karaush-Karmazin, Rashid R. Valiev, Gleb V. Baryshnikov, Valentina A. Minaeva, B. F. Minaev, Hans Ågren, and Department
- Subjects
Materials science ,Absorption spectroscopy ,116 Chemical sciences ,Circulene ,BASIS-SET ,General Physics and Astronomy ,гетеро[8]циркулены ,02 engineering and technology ,Electronic structure ,Ring (chemistry) ,114 Physical sciences ,01 natural sciences ,DENSITY-FUNCTIONAL THEORY ,chemistry.chemical_compound ,RAMAN ,FRANCK-CONDON ,DESIGN ,SULFLOWER ,0103 physical sciences ,SPECTRA ,Physical and Theoretical Chemistry ,ароматичность ,010304 chemical physics ,PHOSPHORESCENCE ,Aromaticity ,021001 nanoscience & nanotechnology ,Internal conversion (chemistry) ,фотофизическое поведение ,MOLECULAR-ORBITAL METHODS ,Crystallography ,электронные спектры поглощения ,SINGLE ,chemistry ,Excited state ,0210 nano-technology ,Sulflower - Abstract
The electronic structure, absorption and emission spectra, aromaticity and photophysical behavior of the recently synthesized tetrasilatetrathia[8]circulene and tetragermatetrathia[8]circulene compounds have been studied computationally. Both compounds demonstrate a specific bifacial aromaticity, which is unusual for hetero[8]circulenes; the inner eight-membered core sustains an expected strong paratropic magnetically-induced ring current, while the outer perimeter contains saturated Si(Et)2 and Ge(Et)2 moieties which break the conjugation between the thiophene rings. The overall magnetically-induced ring current for both studied circulenes is close to zero because of the strong local diatropic currents in each thiophene ring that compensate the paratropic counterpart. The electronic absorption and emission spectra of tetrasilatetrathia[8]circulene and tetragermatetrathia[8]circulene demonstrate a clear visible vibronic progression. The 0–0 band is the most active one in the absorption spectra, while in the fluorescence spectra the 0–1 band composed of several normal vibrations is more intense compared with the 0–0 band in excellent agreement with experiment. Accounting for spin–orbit coupling effects, an analysis of the photophysical constants for the two compounds demonstrates: (1) a clear manifestation of the internal heavy atom effect on the inter-system crossing efficiency; (2) one to two order domination of non-radiative rates over the fluorescence rate; and (3) that the S1–S0 internal conversion is extremely slow and can not compete with the fluorescence, while the S1–Tn inter-system crossing is a main deactivation channel of the S1 excited state. These results provide new insight into the electronic structure and photophysics of tetrasilatetrathia[8]circulene and tetragermatetrathia[8]circulene as novel standalone representatives of hetero[8]circulenes – tetraannelated derivatives of tetrathienylene.
- Published
- 2019
25. Single-layer polymeric tetraoxa[8]circulene modified by s-block metals : toward stable spin qubits and novel superconductors
- Author
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Lyudmila V. Begunovich, Rashid R. Valiev, Gleb V. Baryshnikov, Hans Ågren, Artem V. Kuklin, and Department of Chemistry
- Subjects
Superconductivity ,Materials science ,Condensed matter physics ,Fermi level ,116 Chemical sciences ,Circulene ,02 engineering and technology ,Electronic structure ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,symbols.namesake ,Qubit ,Density of states ,symbols ,General Materials Science ,0210 nano-technology ,Doublet state ,Spin-½ - Abstract
Tunable electronic properties of low-dimensional materials have been the object of extensive research, as such properties are highly desirable in order to provide flexibility in the design and optimization of functional devices. In this study, we account for the fact that such properties can be tuned by embedding diverse metal atoms and theoretically study a series of new organometallic porous sheets based on two-dimensional tetraoxa[8]circulene (TOC) polymers doped with alkali or alkaline-earth metals. The results reveal that the metal-decorated sheets change their electronic structure from semiconducting to metallic behaviour due to n-doping. Complete active space self-consistent field (CASSCF) calculations reveal a unique open-shell singlet ground state in the TOC-Ca complex, which is formed by two closed-shell species. Moreover, Ca becomes a doublet state, which is promising for magnetic quantum bit applications due to the long spin coherence time. Ca-doped TOC also demonstrates a high density of states in the vicinity of the Fermi level and induced superconductivity. Using the ab initio Eliashberg formalism, we find that the TOC-Ca polymers are phonon-mediated superconductors with a critical temperature T-C = 14.5 K, which is within the range of typical carbon based superconducting materials. Therefore, combining the proved superconductivity and the long spin lifetime in doublet Ca, such materials could be an ideal platform for the realization of quantum bits.
- Published
- 2021
26. Franck-Condon factors and vibronic patterns of singlet-triplet transitions of 16O3 molecule falling near the dissociation threshold and above
- Author
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O. V. Egorov, Rashid R. Valiev, Vladimir G. Tyuterev, and Theo Kurtén
- Subjects
Physics ,Radiation ,Франка-Кондона факторы ,010304 chemical physics ,Absorption spectroscopy ,порог диссоциации ,Ab initio ,010402 general chemistry ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Dissociation (psychology) ,0104 chemical sciences ,Atomic electron transition ,молекула озона ,Excited state ,триплетное состояние ,0103 physical sciences ,синглет-триплетные переходы ,medicine ,Singlet state ,medicine.symptom ,Atomic physics ,Ground state ,Spectroscopy ,Basis set - Abstract
The Franck-Condon factors were calculated for vertical electronic transitions between the ground singlet (X1 A1 ) and 3 A2 , 3 B2 , and 3 B1 excited triplet states associated with the Wulf band of the ozone molecule (O3 ). The XMCQDPT2 ab initio method including the static and dynamic electronic correlations was used with the aug-cc-pVQZ basis set. Along with the cold bands, a list of the strongest singlet-triplet hot bands falling into the region of the dissociation threshold of O3 is presented. The absorption coefficient simulated for intensities of the electronic-vibrational patterns agrees well with the measured absorbance from literature. In addition, the intensities of the single lines of the electronic-vibrational-rotational transitions were calculated in absolute units for the most pronounced singlet-triplet hot bands located up to the first 3A2 (0 0 0)←X1 A1 (0 0 0) cold band inclusively. The integrated intensity of the 3 A2 (0 0 0)←X1 A1 (0 0 0) band reported in this work agrees well with the available experimental value from literature.
- Published
- 2021
27. Dianthracenylazatrioxa[8]circulene:Synthesis, Characterization and Application in OLEDs
- Author
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Khrystyna Ivaniuk, Rashid R. Valiev, Boris F. Minaev, Fadhil S. Kamounah, Glib V. Baryshnikov, Viktor Bliksted Roug Pedersen, Michael Pittelkow, Nataliya N. Karaush-Karmazin, Pavlo Stakhira, Stephan K. Pedersen, Line Broløs, Hans Ågren, INAR Physical Chemistry, and Department of Chemistry
- Subjects
Electron mobility ,synthesis ,MOLECULAR DESIGN ,CYCLOOCTATETRATHIOPHENE ,116 Chemical sciences ,polycyclic aromatic hydrocarbons ,LIGHT-EMITTING-DIODES ,Circulene ,PLANAR ,циркулены ,Electroluminescence ,Efficiency, Organizational ,010402 general chemistry ,01 natural sciences ,Catalysis ,ELECTRONIC-STRUCTURE CALCULATIONS ,law.invention ,law ,OLED ,circulene ,EXCIMER FORMATION ,органические светодиоды ,AROMATICITY ,010405 organic chemistry ,business.industry ,Chemistry ,Organic Chemistry ,anthracene ,PAH ,General Chemistry ,PERFORMANCE ,organic light-emitting diodes ,0104 chemical sciences ,Organic semiconductor ,Quantum dot ,оптические свойства ,ANTHRACENE-DERIVATIVES ,Optoelectronics ,Quantum efficiency ,business ,Light-emitting diode - Abstract
A soluble, green-blue fluorescent, pi-extended azatrioxa[8]circulene was synthesized by oxidative condensation of a 3,6-dihydroxycarbazole and 1,4-anthraquinone by using benzofuran scaffolding. This is the first circulene to incorporate anthracene within its carbon framework. Solvent-dependent fluorescence and bright green electroluminescence accompanied by excimer emission are the key optical properties of this material. The presence of sliding pi-stacked columns in the single crystal of dianthracenylazatrioxa[8]circulene is found to cause a very high electron-hopping rate, thus making this material a promising n-type organic semiconductor with an electron mobility predicted to be around 2.26 cm(2) V-1 s(-1). The best organic light-emitting diode (OLED) device based on the dianthracenylazatrioxa[8]circulene fluorescent emitter has a brightness of around 16 000 Cd m(-2) and an external quantum efficiency of 3.3 %. Quantum dot-based OLEDs were fabricated by using dianthracenylazatrioxa[8]circulene as a host matrix material.
- Published
- 2021
28. Aromaticity of Even-Number Cyclo[n]carbons (n=6-100)
- Author
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Theo Kurtén, Rashid R. Valiev, Dage Sundholm, Rinat T. Nasibullin, Glib V. Baryshnikov, Hans Ågren, and Department of Chemistry
- Subjects
CURRENTS ,116 Chemical sciences ,DENSITY FUNCTIONALS ,chemistry.chemical_element ,CARBON RINGS ,Electronic structure ,010402 general chemistry ,Ring (chemistry) ,01 natural sciences ,Physical Chemistry ,114 Physical sciences ,Article ,Delocalized electron ,DESIGN ,0103 physical sciences ,ELEMENTS ,Molecule ,ALL-CARBOATOMIC RING ,Physical and Theoretical Chemistry ,FIELD ,BASIS-SETS ,Fysikalisk kemi ,010304 chemical physics ,Aromaticity ,Triple bond ,0104 chemical sciences ,MOLECULAR-ORBITAL METHODS ,Crystallography ,ELECTRONIC-STRUCTURE ,chemistry ,Carbon ,Antiaromaticity - Abstract
The recently synthesized cyclo[18]carbon molecule has been characterized in a number of studies by calculating electronic, spectroscopic, and mechanical properties. However, cyclo[18] carbon is only one member of the class of cyclo[n]carbons-standalone carbon allotrope representatives. Many of the larger members of this class of molecules have not been thoroughly investigated. In this work, we calculate the magnetically induced current density of cyclo[n]carbons in order to elucidate how electron delocalization and aromatic properties change with the size of the molecular ring (n), where n is an even number between 6 and 100. We find that the Hiickel rules for aromaticity (4k + 2) and antiaromaticity (4k) become degenerate for large C-n rings (n > 50), which can be understood as a transition from a delocalized electronic structure to a nonaromatic structure with localized current density fluxes in the triple bonds. Actually, the calculations suggest that cyclo[n]carbons with n > 50 are nonaromatic cyclic polyalkynes. The influence of the amount of nonlocal exchange and the asymptotic behavior of the exchange-correlation potential of the employed density functionals on the strength of the magnetically induced ring current and the aromatic character of the large cyclo[n]carbons is also discussed.
- Published
- 2020
29. The effect of anion complexation on the aromatic properties of aromatic and antiaromatic porphyrinoids
- Author
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Heike Fliegl, Dage Sundholm, Rashid R. Valiev, Lenara I. Valiulina, and Department of Chemistry
- Subjects
ENERGIES ,116 Chemical sciences ,010402 general chemistry ,Ring (chemistry) ,Photochemistry ,01 natural sciences ,Catalysis ,DESIGN ,CURRENT DENSITIES ,Materials Chemistry ,Molecule ,chemistry.chemical_classification ,010405 organic chemistry ,Chemistry ,CHARACTER ,PATHWAYS ,Aromaticity ,General Chemistry ,Time-dependent density functional theory ,0104 chemical sciences ,THERMOCHEMISTRY ,Hydrocarbon ,13. Climate action ,Excited state ,Density functional theory ,Antiaromaticity - Abstract
The effect of anion complexation on magnetically induced current densities and excitation energies of antiaromatic molecular rings has been investigated by calculations on expanded antiaromatic porphyrinoids including orangarin, rosarin, amethyrin and on a theoretically predicted strongly antiaromatic hydrocarbon ring. Magnetically induced current densities and the lowest vertical excitation energies have been calculated at the density functional theory (DFT) and time-dependent DFT (TDDFT) levels using the M06-2X functional. Similar calculations have been performed on sapphyrin, cyclo[6]carbon and rubyrin, which are aromatic expanded porphyrinoids. The calculations show that anion complexation weakens the strength of the ring currents and the degree of (anti)aromaticity of the studied porphyrinoids and the antiaromatic hydrocarbon ring, because electronic charge is transferred from the anion to the molecular ring. The anion complexation weakens the calculated ring-current strength susceptibility of the antiaromatic porphyrinoids by 5-7 nA T-1 (25-30%), by 6-16 nA T-1 (21-48%) for the aromatic porphyrinoids, and by 8 nA T-1 (27%) for the antiaromatic hydrocarbon ring, whereas the current-density pathways remain the same for most molecules. Calculations on the lowest excited states show that the electronic excitation transfers electron density from the anion to the molecular ring. An antiaromatic heterocyclic molecular ring with five inner NH moieties that was constructed from the antiaromatic hydrocarbon ring was found to have a large Cl- complexation energy of 67.6 kcal mol(-1).
- Published
- 2020
30. First-principles calculations of anharmonic and deuteration effects on the photophysical properties of polyacenes and porphyrinoids
- Author
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Theo Kurtén, Boris F. Minaev, Glib V. Baryshnikov, Hans Ågren, Dage Sundholm, Victor N. Cherepanov, Rinat T. Nasibullin, Rashid R. Valiev, and Department of Chemistry
- Subjects
Materials science ,116 Chemical sciences ,Circulene ,INTERNAL-CONVERSION ,General Physics and Astronomy ,Quantum yield ,010402 general chemistry ,01 natural sciences ,Molecular physics ,114 Physical sciences ,chemistry.chemical_compound ,Reaction rate constant ,MATRIX-ELEMENTS ,RATE CONSTANTS ,0103 physical sciences ,Tetraphenylporphyrin ,MORSE OSCILLATOR MODEL ,RATES ,Physical and Theoretical Chemistry ,FLUORESCENCE ,Anthracene ,COMPLEX ,010304 chemical physics ,RADIATIONLESS ELECTRONIC-TRANSITIONS ,Anharmonicity ,Internal conversion (chemistry) ,Porphyrin ,0104 chemical sciences ,chemistry ,13. Climate action ,ORGANIC-MOLECULES ,SPIN-ORBIT - Abstract
A new method for calculating internal conversion rate constants (k[combining low line]IC), including anharmonic effects and using the Lagrangian multiplier technique, is proposed. The deuteration effect on k[combining low line]IC is investigated for naphthalene, anthracene, free-base porphyrin (H2P) and tetraphenylporphyrin (H2TPP). The results show that anharmonic effects are important when calculating k[combining low line]IC for transitions between electronic states that are energetically separated (ΔE) by more than 20 000-25 000 cm-1. Anharmonic effects are also important when ΔE20 000-25 000 cm-1 and when the accepting modes are X-H stretching vibrations with a frequency larger than 2000 cm-1. The calculations show that there is mixing between the S1 and S2 states of naphthalene induced by non-adiabatic interactions. The non-adiabatic interaction matrix element between the S1 and S2 states is 250 cm-1 and 50 cm-1 for the normal and fully deuterated naphthalene structure and this difference significantly affects the estimated fluorescence quantum yield. Besides aromatic hydrocarbons H2P and H2TPP, the k[combining low line]IC rate constant is also calculated for pyrometene (PM567) and tetraoxa[8]circulene (4B) with a detailed analysis of the effect of the vibrational anharmonicity.
- Published
- 2020
31. Perhalophenyl Three-Coordinate Gold(I) Complexes as TADF Emitters : A Photophysical Study from Experimental and Computational Viewpoints
- Author
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José M. López-de-Luzuriaga, María Rodríguez-Castillo, Dage Sundholm, Inés Soldevilla, M. Elena Olmos, Miguel Monge, Rashid R. Valiev, and Department of Chemistry
- Subjects
116 Chemical sciences ,Solid-state ,LIGHT-EMITTING-DIODES ,010402 general chemistry ,01 natural sciences ,Inorganic Chemistry ,chemistry.chemical_compound ,Reaction rate constant ,ADDUCTS ,CHEMISTRY ,Chelation ,COPPER(I) COMPLEXES ,Physical and Theoretical Chemistry ,Benzene ,ACTIVATED DELAYED FLUORESCENCE ,Trigonal planar molecular geometry ,COORDINATION ,010405 organic chemistry ,Chemistry ,TRIPHENYLPHOSPHINE ,Fluorescence ,0104 chemical sciences ,3. Good health ,Crystallography ,Intersystem crossing ,METAL ,LUMINESCENCE ,LIGANDS ,Phosphorescence - Abstract
We report the synthesis of novel perhalophenyl three- coordinated gold( I) complexes using 1,2- bis-(diphenylphosphino)benzene (dppBz) as the chelating ligand and [AuR(tht)] (R = C6F5, C6Cl2F3, C6Cl5) as the perhalophenyl-gold(I) source, leading to [AuR(dppBz)] (R = C6F5 (1), C6Cl2F3 (2), C6Cl5 (3)) complexes. The solid-state structures of compounds 2 and 3 consist of discrete three-coordinated Au(I) complexes, which show a distorted trigonal planar geometry for the gold center with dissimilar Au-P distances. The distorted structural arrangement is closely related to its photophysical properties. The studied complexes display very intense emissions at room temperature (RT) and at 77 K in the solid state. Studies of the emissive properties of the complexes at different temperatures suggest that the emissions are phosphorescent at 77 K and exhibit thermally activated delayed fluorescence (TADF) at RT. First-principle calculations of the photophysical processes yielded rate constants for intersystem crossing and reverse intersystem crossing that are in excellent agreement with experimental data.
- Published
- 2020
32. Comparing Reaction Routes for
- Author
-
Galib, Hasan, Vili-Taneli, Salo, Rashid R, Valiev, Jakub, Kubečka, and Theo, Kurtén
- Abstract
Organic peroxy radicals (RO
- Published
- 2020
33. Can Plasmon Change Reaction Path? Decomposition of Unsymmetrical Iodonium Salts as an Organic Probe
- Author
-
Rashid R. Valiev, Polina Bainova, Roman Elashnikov, Oleksiy Lyutakov, Mohamed M. Chehimi, Natalia S. Soldatova, Olga Guselnikova, Přemysl Fitl, Vaclav Svorcik, Pavel S. Postnikov, Elena Miliutina, Mekhman S. Yusubov, Theo Kurtén, Doctoral Programme in Chemistry and Molecular Sciences, Doctoral Programme in Atmospheric Sciences, and Department of Chemistry
- Subjects
One-pot synthesis ,116 Chemical sciences ,010402 general chemistry ,Photochemistry ,01 natural sciences ,Dissociation (chemistry) ,Catalysis ,SELECTIVE HYDROGENATION ,AG NANOSTRUCTURES ,Physics::Atomic and Molecular Clusters ,ARYL IODIDES ,General Materials Science ,Physical and Theoretical Chemistry ,Physics::Chemical Physics ,HOMO/LUMO ,Plasmon ,010405 organic chemistry ,Chemistry ,CATALYSIS ,DISSOCIATION ,DRIVEN ,DIARYLIODONIUM SALTS ,Decomposition ,0104 chemical sciences ,ONE-POT SYNTHESIS ,Chemical energy ,REDUCTION ,Surface modification ,FUNCTIONALIZATION - Abstract
Plasmon-assisted transformations of organic compounds represent a novel opportunity for conversion of light to chemical energy at room temperature. However, the mechanistic insights of interaction between plasmon energy and organic molecules is still under debate. Herein, we proposed a comprehensive study of the plasmon-assisted reaction mechanism using unsymmetric iodonium salts (ISs) as an organic probe. The experimental and theoretical analysis allow us to exclude the possible thermal effect or hot electron transfer. We found that plasmon interaction with unsymmetrical ISs led to the intramolecular excitation of electron followed by the regioselective cleavage of C–I bond with the formation of electron-rich radical species, which cannot be explained by the hot electron excitation or thermal effects. The high regioselectivity is explained by the direct excitation of electron to LUMO with the formation of a dissociative excited state according to quantum-chemical modeling, which provides novel opportunities for the fine control of reactivity using plasmon energy.
- Published
- 2020
34. Photophysical properties of the triangular [Au(HN[double bond, length as m-dash]COH)]
- Author
-
Jonas, Greiner, Rashid R, Valiev, and Dage, Sundholm
- Abstract
Rate constants for radiative and non-radiative transitions of the [Au(HN[double bond, length as m-dash]COH)]3 complex and its dimer were calculated within the Herzberg-Teller approximation based on quantum mechanical principles. A high triplet quantum yield was estimated for the monomer. Internal conversion (IC) was found to be the major competing process to the intersystem crossing (ISC) from the lowest excited singlet state (S1) to the lowest triplet state (T1). ISC and IC from the spin-mixed T[combining tilde]1 state also dominate the triplet relaxation process resulting in a negligible phosphorescence quantum yield for the monomer. The IC and ISC rate constants of the dimer are considerably smaller due to much lower Franck-Condon factors. For the dimer a triplet quantum yield of 0.71 was estimated using the extended multi-configuration quasi-degenerate second-order perturbation theory (XMCQDPT2) method to calculate the transition energies. Fluorescence is the major competing process to the ISC relaxation of the S1 state of the dimer. The ISC and IC processes are insignificant for the relaxation of the T1 state, resulting in unity phosphorescence quantum yield. The high triplet and phosphorescence quantum yields of the [Au(HN[double bond, length as m-dash]COH)]3 dimer make it and its higher oligomers potential candidates as dopants for phosphorescent organic light emitting diodes and as down-converters in solid-state lighting systems.
- Published
- 2020
35. Computational studies of gas-phase accretion product formation involving RO2
- Author
-
Vili-Taneli Salo, Galib Hasan, Rashid R. Valiev, Siddharth Iyer, Matti P. Rissanen, and Theo Kurtén
- Subjects
Physics ,Product formation ,Astrophysics ,Gas phase ,Accretion (finance) - Abstract
Field and laboratory studies have indirectly but conclusively established that reactions involving peroxy radicals (RO2) play a key role in the gas-phase formation of accretion products, also commonly referred to as “dimers”, as they typically contain roughly twice the number of carbon atoms compared to their hydrocarbon precursors. Using computational tools, we have recently presented two different potential mechanisms for this process.First, direct and rapid recombination of peroxy and alkoxy (RO) radicals, analogous to the recently characterized RO2 + OH reaction, leads to the formation of metastable RO3R’ trioxides, which may have lifetimes on the order of a hundred seconds. [1] However, due to both the limited lifetime of the trioxides, and the low concentration of alkoxy radicals, the RO2 + R’O pathway is likely to be a minor, though not necessarily negligible, pathway for atmospheric dimer formation.Second, we have shown that recombination of two peroxy radicals – phenomenologically known to be responsible for the formation of ROOR’ – type dimers – very likely occurs through a multi-step mechanism involving an intersystem crossing (ISC). [2] In contrast to earlier predictions, we find that the rate-limiting step for the overall RO2 + R’O2 reaction is the initial formation of a short-lived RO4R’ tetroxide intermediate. For tertiary RO2, the barrier for the tetroxide formation can be substantial. However, for all studied species the tetroxide decomposition is rapid, forming ground-state triplet O2, and a weakly bound triplet complex of two alkoxy radicals. The branching ratios of the different RO2 + R’O2 reaction channels are then determined by a three-way competition of this complex. For simple systems, the possible channels are dissociation (leading to RO + R’O), H-abstraction on the triplet surface (leading to RC=O + R’OH), and ISC and subsequent recombination on the singlet surface (leading to ROOR’). All of these can potentially be competive with each other, with rates very roughly on the order of 109 s-1. For more complex RO2 parents, rapid unimolecular reactions of the daughter RO (such as alkoxy scissions) open up even more potential reaction channels, for example direct alkoxy – alkyl recombination to form (either singlet or triplet) ether-type (ROR’) dimers.[1] Iyer, S., Rissanen, M. P. and Kurtén, T. Reaction Between Peroxy and Alkoxy Radicals can Form Stable Adducts. Journal of Physical Chemistry Letters, Vol. 10, 2051-2057, 2019.[2] Valiev, R., Hasan, G., Salo, V.-T., Kubečka, J. and Kurtén, T. Intersystem Crossings Drive Atmospheric Gas-Phase Dimer Formation. Journal of Physical Chemistry A, Vol. 123, 6596-6604, 2019.
- Published
- 2020
36. Rapid formation of HOMs from gas-phase alpha-pinene ozonolysis
- Author
-
Siddharth Iyer, Matti P. Rissanen, Joel A. Thornton, Rashid R. Valiev, and Theo Kurtén
- Subjects
alpha-Pinene ,chemistry.chemical_compound ,Ozonolysis ,Chemistry ,Organic chemistry ,Gas phase - Abstract
Alpha-pinene is the largest globally emitted monoterpene. Its oxidation reaction with ozone leads to peroxy radicals (RO2) that can subsequently form highly oxygenated organic molecules (HOMs) through the process of autoxidation. HOMs are considered to play a critical role in the growth of early particles as they can have sufficiently low saturation vapor pressures.Pseudo-unimolecular autoxidation reaction is generally thought to compete with bimolecular reactions of RO2in the atmosphere. While these bimolecular reactions could potentially lead to radical recycling, [1] they are generally thought to lead to the formation of non-reactive products. In order to compete with these bimolecular reactions, the unimolecular autoxidation reaction must be rapid, especially in high RO2/NO conditions.The initial ozonolysis reaction of a-pinene leads to the first-generation RO2with the 6-member ring broken. Current knowledge dictates the perpetuation of the inner 4-member cylobutyl ring in the first-generation RO2. This ring has proven to be a hurdle for rapid unimolecular autoxidation reactions as the steric hindrance the ring affords leads to high barriers (and therefore slow reaction rates) for hydrogen-shift (H-shift) reactions central to autoxidation. [2]In this work, we show that the ozonolysis of a-pinene could directly lead to the formation of a hitherto unexplored completely ring-opened RO2 product. This pathway is made feasible by considering the large amount of excess energy channeled into the rovibrational modes of the vinoxy product after ozonolysis. This leads to the opening of the cyclobutyl ring of a significant fraction of the “hot” vinoxy radicals under atmospheric conditions, as opposed to all of them adding an O2molecule as was previously thought. The breaking of the ring potentially leads to the formation of products with up to 8 oxygen atoms after a single hydrogen shift reaction following the formation of the vinoxy. [1] Iyer, S.; Reiman, H.; Møller, K. H.; Rissanen, M. P.; Kjaergaard, H. G.; Kurtén, T. Computational Investigation of RO2+ HO2and RO2+ RO2Reactions of Monoterpene Derived First-Generation Peroxy Radicals Leading to Radical Recycling. J. Phys. Chem. A2018, 49, 9542-9552.[2] Kurtén, T.; Rissanen, M. P. Rissanen, Mackeprang, K.; Thornton, J. A.; Jørgensen, S.; Ehn, M.; Kjaergaard, H. G. Computational Study of Hydrogen Shifts and Ring-Opening Mechanisms in a-Pinene Ozonolysis Products. J. Phys. Chem. A2015, 119, 11366-11375.
- Published
- 2020
37. Photolysis of diatomic molecules as a source of atoms in planetary exospheres
- Author
-
Chrisitan Wöhler, Rashid R. Valiev, I. S. Gritsenko, Viktor N. Cherepanov, Theo Kurtén, Alexey A. Berezhnoy, B.S. Merzlikin, and Department of Chemistry
- Subjects
010504 meteorology & atmospheric sciences ,molecular data ,stars: kinematics and dynamics ,116 Chemical sciences ,Analytical chemistry ,Ab initio ,sradiation mechanisms: general ,Astrophysics ,Kinetic energy ,01 natural sciences ,7. Clean energy ,Quantum chemistry ,CROSS-SECTIONS ,Metal ,FRANCK-CONDON ,ALKALI ,CHEMISTRY ,ELECTRONIC STATES ,0103 physical sciences ,Molecule ,010303 astronomy & astrophysics ,0105 earth and related environmental sciences ,IMPACT EVENTS ,Physics ,AB-INITIO ,ultraviolet: planetary systems ,Photodissociation ,Astronomy and Astrophysics ,Alkali metal ,Diatomic molecule ,LINE LISTS ,SODIUM ,molecular processes ,meteorites, meteors, meteoroids ,PHOTODISSOCIATION PROCESSES ,13. Climate action ,Space and Planetary Science ,visual_art ,visual_art.visual_art_medium - Abstract
We calculated the cross sections of photolysis of OH, LiO, NaO, KO, HCl, LiCl, NaCl, KCl, HF, LiF, NaF, and KF molecules using quantum chemistry methods. The maximal values for photolysis cross sections of alkali metal monoxides are on the order of 10−18 cm2. The lifetimes of photolysis for quiet Sun at 1 astronomical unit are estimated as 2.0 × 105, 28, 5, 14, 2.1 × 105, 225, 42, 52, 2 × 106, 35 400, 486, and 30 400 s for OH, LiO, NaO, KO, HCl, LiCl, NaCl, KCl, HF, LiF, NaF, and KF, respectively. We performed a comparison between values of photolysis lifetimes obtained in this work and in previous studies. Based on such a comparison, our estimations of photolysis lifetimes of OH, HCl, and HF have an accuracy of about a factor of 2. We determined typical kinetic energies of main peaks of photolysis-generated metal atoms. Impact-produced LiO, NaO, KO, NaCl, and KCl molecules are destroyed in the lunar and Hermean exospheres almost completely during the first ballistic flight, while other considered molecules are more stable against destruction by photolysis.
- Published
- 2020
38. Competition between the nonadiabatic electronic state-mixing and the Herzberg-Teller vibronic effects in fluorescence process of tetraoxa[8] circulene
- Author
-
Rashid R. Valiev and Department of Chemistry
- Subjects
Jahn-Teller effect ,Jahn–Teller effect ,Nonadiabatic electronic state-mixing effect ,116 Chemical sciences ,Ab initio ,Circulene ,General Physics and Astronomy ,02 engineering and technology ,01 natural sciences ,Molecular physics ,Herzberg-Teller vibronic effect ,114 Physical sciences ,Spectral line ,FRANCK-CONDON ,0103 physical sciences ,Vibronic spectroscopy ,SPECTRA ,Symmetry breaking ,Physical and Theoretical Chemistry ,Mixing (physics) ,AROMATICITY ,Physics ,AB-INITIO ,010304 chemical physics ,Hetero[8]circulenes ,Tetraoxa[8]circulene ,Aromaticity ,Vibronic spectra ,021001 nanoscience & nanotechnology ,SIMULATION ,0210 nano-technology - Abstract
The effect of the nonadiabatic electronic state-mixing between the S-1 and S-2 states in tetraoxa[8]circulene is investigated computationally. The calculations show that the nonadiabatic electronic state-mixing effect on the fluorescence of tetraoxa[8]circulene is one million times weaker than the Herzberg-Teller vibronic effect. Analysis of the promotive modes of the S-0 -> S-1 and S-1 -> S-0 transitions shows that they are same for both absorption and emission. Also, the Duschinsky effect is found to be very weak for the S-0 -> S-1 and S-1 -> S-0 transitions. The Jahn-Teller symmetry breaking of the S-2 state leads to an energy splitting of similar to 1500 cm(-1) between the two components of the S-2 state.
- Published
- 2020
39. Vibronic absorption spectra of the angular fused bisindolo- and biscarbazoloanthracene blue fluorophores for OLED applications
- Author
-
Gleb V. Baryshnikov, Rashid R. Valiev, Boris F. Minaev, Dmitry A. Sunchugashev, and Hans Ågren
- Subjects
Anthracene ,010304 chemical physics ,Absorption spectroscopy ,General Physics and Astronomy ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Photochemistry ,01 natural sciences ,chemistry.chemical_compound ,chemistry ,0103 physical sciences ,OLED ,Vibronic spectroscopy ,Physical and Theoretical Chemistry ,0210 nano-technology - Abstract
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:3â²,4â²-h]anthracene has ...
- Published
- 2018
40. Computational study of aromaticity, 1H NMR spectra and intermolecular interactions of twisted thia-norhexaphyrin and its multiply annulated polypyrrolic derivatives
- Author
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Rashid R. Valiev, Chengjie Li, Hans Ågren, Yongshu Xie, Gleb V. Baryshnikov, Qizhao Li, and Department of Chemistry
- Subjects
Proton ,Chemistry ,Hydrogen bond ,Chemical shift ,Atoms in molecules ,Intermolecular force ,116 Chemical sciences ,General Physics and Astronomy ,Aromaticity ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Computational chemistry ,Intramolecular force ,Proton NMR ,Physical and Theoretical Chemistry ,0210 nano-technology - Abstract
The recently synthesized twisted thia-norhexaphyrin and its multiply annulated polypyrrolic derivatives have been studied computationally. Gauge-including magnetically induced current calculations predict a global nonaromatic character of the initial thia-norhexaphyrin due to the highly-twisted conformation of the macrocycle. Upon the oxidation of the thia-norhexaphyrin the four multiply annulated polypyrrolic aromatic macrocycles are formed for which the global aromatic character is confirmed in agreement with experimentally measured 1H NMR spectra. The calculations of the proton chemical shifts for the studied compounds by direct comparison with the tetramethylsilane standard leads to a significant mean absolute error. At the same time a linear regression procedure for the two selected groups of protons (CH and NH protons) provides much better values of calculated chemical shifts and tight correlation with experiment. The separate consideration of NH protons is motivated by the numerous intermolecular hydrogen bonds in which the protons are involved that induce considerable upfield shifts leading to the significant underestimation of corresponding chemical shifts. Such a selected correlation can be used for accurate estimation of proton chemical shifts of the related porphyrinoids. Bader's theory of Atoms in Molecules has been applied for the studied twisted thia-norhexaphyrin and its multiply annulated polypyrrolic derivatives to characterize the intramolecular H-bonds and other non-covalent interactions.
- Published
- 2019
41. Computational study of aromaticity
- Author
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Gleb V, Baryshnikov, Rashid R, Valiev, Qizhao, Li, Chengjie, Li, Yongshu, Xie, and Hans, Ågren
- Abstract
The recently synthesized twisted thia-norhexaphyrin and its multiply annulated polypyrrolic derivatives have been studied computationally. Gauge-including magnetically induced current calculations predict a global nonaromatic character of the initial thia-norhexaphyrin due to the highly-twisted conformation of the macrocycle. Upon the oxidation of the thia-norhexaphyrin four multiply annulated polypyrrolic aromatic macrocycles are formed for which the global aromatic character is confirmed in agreement with experimentally measured
- Published
- 2019
42. The blue vibronically resolved electroluminescence of azatrioxa[8]circulene
- Author
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Rashid R. Valiev, Ruslan M. Gadirov, Stephan K. Pedersen, Konstantin M. Degtyarenko, Michael Pittelkow, D V Grigoryev, B. F. Minaev, Gleb V. Baryshnikov, R.T. Nasubullin, Department, and Department of Chemistry
- Subjects
Brightness ,Materials science ,116 Chemical sciences ,Circulene ,переходная электролюминесценция ,General Physics and Astronomy ,02 engineering and technology ,Electroluminescence ,EMISSION BANDS ,01 natural sciences ,7. Clean energy ,114 Physical sciences ,органическое светоизлучающие устройства ,Molecular electronic transition ,Spectral line ,FRANCK-CONDON ,0103 physical sciences ,OLED ,Vibronic spectroscopy ,SPECTRA ,Emission spectrum ,Physical and Theoretical Chemistry ,Blue emission ,010304 chemical physics ,business.industry ,вибронные спектры ,Transition electroluminescence ,Vibronic spectra ,021001 nanoscience & nanotechnology ,Organic light emitting device ,синяя эмиссия ,SIMULATION ,Optoelectronics ,0210 nano-technology ,business - Abstract
Organic Light Emitting Dioides (OLED)devices were fabricated with blue emission based on azatrioxa[8]circulene and 4,4-N,N'-Dicarbazolyl-1,1'-biphenyl (CBP) with maximum brightness of 840 kd/m(2) at 12 V and the starting voltage of 3.5 V. The vibronic emission spectrum was analyzed by the promotive modes calculation method. The electroluminescence of fabricated OLED device is caused by the 0-0 electronic transition and single excitations of 1473 cm(-1) and 1673 cm(-1) modes and combinations thereof.
- Published
- 2019
43. Optical tuning of tetrabenzo[8]circulene derivatives through pseudorotational conformational isomerization
- Author
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Boris F. Minaev, Gleb V. Baryshnikov, Hans Ågren, and Rashid R. Valiev
- Subjects
Materials science ,Absorption spectroscopy ,010405 organic chemistry ,Computational chemistry ,Process Chemistry and Technology ,General Chemical Engineering ,Circulene ,OLED ,Conformational isomerization ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences - Abstract
In order to further search efficient [8]circulene materials for OLED applications we have theoretically investigated the structure and electronic, absorption spectra of functionalized tetrabenzo[8] ...
- Published
- 2018
44. Verdazyl Radical Building Blocks: Synthesis, Structure, and Sonogashira Cross-Coupling Reactions
- Author
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Ekaterina Andreevna Martynko, Marina E. Trusova, Rashid R. Valiev, Pavel S. Postnikov, Pavel V. Petunin, Mikhail N. Uvarov, Maxim S. Kazantsev, Evgeny A. Mostovich, and Tatyana V. Rybalova
- Subjects
010405 organic chemistry ,Chemistry ,Organic Chemistry ,Polymer chemistry ,Sonogashira coupling ,Physical and Theoretical Chemistry ,010402 general chemistry ,01 natural sciences ,Coupling reaction ,0104 chemical sciences - Published
- 2018
45. Reactions of 1-Arylbenziodoxolones with Azide Anion: Experimental and Computational Study of Substituent Effects
- Author
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Thomas Wirth, Natalia S. Soldatova, Pavel S. Postnikov, Roza Y. Yusubova, Akira Yoshimura, Dmitry Y. Svitich, Mekhman S. Yusubov, Rashid R. Valiev, and Viktor V. Zhdankin
- Subjects
010405 organic chemistry ,Aryl ,Organic Chemistry ,Leaving group ,Substituent ,010402 general chemistry ,Ring (chemistry) ,01 natural sciences ,Medicinal chemistry ,0104 chemical sciences ,chemistry.chemical_compound ,chemistry ,Nucleophile ,Nucleophilic substitution ,Reactivity (chemistry) ,Azide ,Physical and Theoretical Chemistry - Abstract
New substituted 1-arylbenziodoxolones were prepared and their reactivity with azide anion nucleophile was investigated. It was found that independent on the presence of substituents, all reactions of 1-arylbenziodoxolones proceed as nucleophilic substitution of the iodonium leaving group in the electron-deficient benziodoxolone benzene ring. The presence of bulky substituents in the ortho-position of the aryl ring slowers the reaction, while the presence of a moderately electron-withdrawing bromine substituent in the para-position to iodine in the benziodoxolone ring moderately increases the rate of substitution. The presence of a strongly electron-withdrawing nitro group in the para-position to iodine in the benziodoxolone ring dramatically increases the rate of substitution. These observations are in agreement with the electronic requirements for internal nucleophilic substitution in the benziodoxole ring. A quantum-chemical computational study of the possible reaction paths is in agreement with the observed effects of substituents on the reactivity of arylbenziodoxolones in this reaction.
- Published
- 2018
46. The aromaticity of verdazyl radicals and their closed-shell charged species
- Author
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Pavel V. Petunin, Dage Sundholm, Marina E. Trusova, Pavel S. Postnikov, Anna K. Drozdova, Victor N. Cherepanov, and Rashid R. Valiev
- Subjects
010405 organic chemistry ,Chemistry ,Radical ,Aromaticity ,General Chemistry ,010402 general chemistry ,Ring (chemistry) ,01 natural sciences ,Catalysis ,0104 chemical sciences ,Chemical physics ,Ionization ,Materials Chemistry ,Molecule ,Open shell ,Ring current ,Antiaromaticity - Abstract
The aromaticity of fourteen 3-oxo-verdazyl (1–8, 15) and Kuhn verdazyl (9–14) radicals with different substituents has been investigated computationally using the gauge-including magnetically induced current-density (GIMIC) method. The strength of the local and global diatropic and paratropic ring current has been obtained by performing numerical integration of the current density flow. Detailed studies of the current densities show that the aromatic character of the verdazyl ring obeys Huckel's aromaticity rule. The cations with formally 6π electrons in the verdazyl ring are weakly aromatic and the anions with 8π electrons are antiaromatic. The verdazyl ring of the neutral radicals is found to be weakly antiaromatic. The studied molecules sustain a significant global diatropic ring current that flows around the verdazyl and the phenyl rings suggesting that there is a strong coupling between the rings. For the 3-oxo-verdazyl cations, the global ring current is weaker. The spin-current density of the radicals is paratropic forming a ring current in the studied 3-oxo-verdazyls, whereas in the Kuhn verdazyls we found that the spin current density is mainly localized on the nitrogens. The calculated ionization potentials are also compared to the values deduced from cyclic voltammetry data.
- Published
- 2018
47. Relations between the aromaticity and magnetic dipole transitions in the electronic spectra of hetero[8]circulenes
- Author
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Rashid R. Valiev, Gleb V. Baryshnikov, Dage Sundholm, and Department of Chemistry
- Subjects
NICS ,Magnetic dipole transition ,116 Chemical sciences ,VALENCE ,Circulene ,General Physics and Astronomy ,02 engineering and technology ,PLANAR ,010402 general chemistry ,114 Physical sciences ,01 natural sciences ,Molecular physics ,DESIGN ,Physics::Atomic and Molecular Clusters ,Physical and Theoretical Chemistry ,Physics ,Valence (chemistry) ,Chemical shift ,Aromaticity ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Excited state ,CHEMICAL-SHIFTS ,0210 nano-technology ,Magnetic dipole ,Antiaromaticity - Abstract
Magnetically induced current densities have been calculated at the second-order MOller-Plesset perturbation theory (MP2) level for seven hetero[8]circulenes and their dicationic and dianionic forms. Calculations of the magnetic dipole transition moments have also been carried out at the algebraic diagrammatic construction (ADC(2)) and the second-order approximate coupled-cluster (CC2) levels. The calculations show that the degree of aromaticity and the size of the magnetic dipole transition moment of the lowest magnetic-dipole allowed excited state are related. We show that neutral hetero[8]circulenes are weakly antiaromatic when the first excited state with a large magnetic dipole transition moment of 10-16 a.u. lies at high energies (approximate to 2.8-3.5 eV). For the dications, this transition often lies at much lower energies. Hetero[8]circulene dications with large magnetic dipole transition moments are strongly antiaromatic. The lowest excited states of the hetero[8]circulene dianions have very small magnetic dipole transition moments implying that they are aromatic.
- Published
- 2018
48. A hybrid molecular sensitizer for triplet fusion upconversion
- Author
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Rashid R. Valiev, Rongwei Fan, Glib V. Baryshnikov, Guanying Chen, Xinyu Wang, Songtao Lu, Xing Wang, and Hans Ågren
- Subjects
Lanthanide ,Ytterbium ,Materials science ,триплеты ,лантаноиды ,General Chemical Engineering ,chemistry.chemical_element ,02 engineering and technology ,010402 general chemistry ,Photochemistry ,01 natural sciences ,7. Clean energy ,Quantum chemistry ,Industrial and Manufacturing Engineering ,Environmental Chemistry ,Dopant ,Photoredox catalysis ,нанокристаллы ,General Chemistry ,021001 nanoscience & nanotechnology ,Photon upconversion ,0104 chemical sciences ,Intersystem crossing ,Nanocrystal ,chemistry ,0210 nano-technology - Abstract
Triplet fusion upconversion is useful for a broad spectrum of applications ranging from solar cells, photoredox catalysis, to biophotonics applications, especially in the near-infrared (NIR, >700 nm) range. This upconverting system typically demands efficient conversion of spin-singlet harvested energy through intersystem crossing to spin-triplet states, accessible only in rare metallic-coordinating macrocycle compounds or heavy-metal-containing semiconductor quantum dots for triplet sensitization. Herein, we describe an organic–inorganic system for NIR-to-visible triplet fusion upconversion, interfacing commonly-seen, non-metallic, infrared dyes (IR806, IR780, indyocynine green, and CarCl) and lanthanide nanocrystal (sodium ytterbium fluoride) as a hybrid molecular sensitizer, which extracts molecular spin-singlet energy to nanocrystal-enriched ytterbium dopants at ~48% efficiency (IR806, photoexciation at 808 nm). Moreover, ytterbium sub-lattice energy migration increases the interaction possibility between the nanocrystal and the freely-diffusing rubrenes in solution, resulting in 24-fold (IR806) to 1740-fold (indocyanine green) upconversion (600 nm) increase, depending on the IR dye type, as compared to the one without ytterbium nanotransducers. Ab initio quantum chemistry calculations identify enhanced spin-orbital coupling in the ytterbium-IR806 complex and high energy transfer rate in the ytterbium-rubrene interaction (1010 s−1). Employing inorganic lanthanide nanocrystals as nanotransducers unleashes the potential use of non-metallic infrared organic dyes for triplet fusion upconversion.
- Published
- 2021
49. Plasmon-assisted MXene grafting: tuning of surface termination and stability enhancement
- Author
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Anastasiya Olshtrem, Sergii Chertopalov, Olga Guselnikova, Rashid R Valiev, Miroslav Cieslar, Elena Miliutina, Roman Elashnikov, Premysl Fitl, Pavel Postnikov, Jan Lancok, Vaclav Svorcik, Oleksiy Lyutakov, Department of Chemistry, and INAR Physical Chemistry
- Subjects
Nanostructure ,Materials science ,116 Chemical sciences ,chemistry.chemical_element ,engineering.material ,plasmon-assisted chemistry and grafting ,NANOSTRUCTURES ,superhydrophobic and self-repellent coating ,Coating ,Moiety ,General Materials Science ,Surface plasmon resonance ,Plasmon ,CATALYSIS ,surface termination ,Mechanical Engineering ,food and beverages ,General Chemistry ,TI3C2 ,Condensed Matter Physics ,chemistry ,Chemical engineering ,Mechanics of Materials ,engineering ,Fluorine ,MXene ,oxidation protection ,MXenes ,Titanium - Abstract
The properties of MXenes, new generation of 2D materials, are determined by the surface terminations, which depends on flake preparation method. Changing the surface termination chemical groups can significantly modify the MXene flake properties and functionality. However, the common methods of MXene flake surface chemistry tuning require high-energy treatments and often lead to flake damage. In this work, we propose a plasmon-assisted chemical transformation for tuning the surface chemistry and termination of MXene flakes. The plasmon resonance was directly excited on MXene flakes and induced the generation of highly reactive radicals from electrostatically absorbed iodonium salt cations, leading to immediate grafting of the created radicals to the flake edges and basal planes. We used bis-CF3-substituted iodonium salts, and subsequent analysis of the Ti3C2Tx MXene flake surface composition indicated decreases in the total oxygen concentration and oxidized titanium with a simultaneous increase in the fluorine surface concentration, which was related to –C6H3(CF3)2 moiety attachment. The ability to substitute the hydrophilic oxygen-containing groups with hydrophobic and oleophilic –CF3 groups containing functional groups allows us to create a stable suspension of a MXene in nonpolar organic solvents and prepare a superhydrophobic, water-repellent and oxidation-stable conductive MXene coating.
- Published
- 2021
50. Photolysis of metal oxides as a source of atoms in planetary exospheres
- Author
-
Alexey A. Berezhnoy, Anna Sidorenko, B.S. Merzlikin, Rashid R. Valiev, and Victor N. Cherepanov
- Subjects
Alkaline earth metal ,Materials science ,010504 meteorology & atmospheric sciences ,Photodissociation ,Ab initio ,Analytical chemistry ,Astronomy and Astrophysics ,Alkali metal ,Kinetic energy ,01 natural sciences ,Quantum chemistry ,Metal ,Space and Planetary Science ,visual_art ,0103 physical sciences ,visual_art.visual_art_medium ,Molecule ,Atomic physics ,010303 astronomy & astrophysics ,0105 earth and related environmental sciences - Abstract
The cross sections of photolysis of LiO, NaO, KO, MgO, and CaO molecules have been calculated by the use of quantum chemistry methods. The maximal values for photolysis cross sections of alkali metal monoxides have the order of 10−17 cm2, and for alkaline earth metal monoxides these values are less on 1–2 orders of the magnitude. The lifetimes of photolysis at 1 astronomical unit are estimated as 5, 3, 60, 70, and 3,000 s for LiO, NaO, KO, MgO, and CaO, respectively. Typical kinetic energies of main peaks of photolysis-generated metal atoms are determined. Impact-produced LiO, NaO, KO, and MgO molecules are destroyed in the lunar and Hermean exospheres almost completely during the first ballistic flight while CaO molecule is more stable against destruction by photolysis. Photolysis-generated metal atoms in planetary exospheres can be detected by performing high-resolution spectral observations of velocity distribution of exospheric metal atoms.
- Published
- 2017
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