First-principles method for calculating the rate constants of internal-conversion and intersystem-crossing transitions

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Valiev , R R , Cherepanov , V N , Baryshnikov , G V & Sundholm , D 2018 , ' First-principles method for calculating the rate constants of internal-conversion and intersystem-crossing transitions ' , Physical Chemistry Chemical Physics , vol. 20 , no. 9 , pp. 6121-6133 . https://doi.org/10.1039/c7cp08703a

Title: First-principles method for calculating the rate constants of internal-conversion and intersystem-crossing transitions
Author: Valiev, R. R.; Cherepanov, V. N.; Baryshnikov, G. V.; Sundholm, D.
Contributor: University of Helsinki, Department of Chemistry
University of Helsinki, Department of Chemistry
Date: 2018-03-07
Language: eng
Number of pages: 13
Belongs to series: Physical Chemistry Chemical Physics
ISSN: 1463-9076
URI: http://hdl.handle.net/10138/310387
Abstract: A method for calculating the rate constants for internal-conversion (k(IC)) and intersystem-crossing (k(ISC)) processes within the adiabatic and Franck-Condon (FC) approximations is proposed. The applicability of the method is demonstrated by calculation of k(IC) and k(ISC) for a set of organic and organometallic compounds with experimentally known spectroscopic properties. The studied molecules were pyrromethene-567 dye, psoralene, hetero[8]circulenes, free-base porphyrin, naphthalene, and larger polyacenes. We also studied fac-Alq(3) and fac-Ir(ppy)(3), which are important molecules in organic light emitting diodes (OLEDs). The excitation energies were calculated at the multi-configuration quasi-degenerate second-order perturbation theory (XMC-QDPT2) level, which is found to yield excitation energies in good agreement with experimental data. Spin-orbit coupling matrix elements, non-adiabatic coupling matrix elements, Huang-Rhys factors, and vibrational energies were calculated at the time-dependent density functional theory (TDDFT) and complete active space self-consistent field (CASSCF) levels. The computed fluorescence quantum yields for the pyrromethene-567 dye, psoralene, hetero[8]circulenes, fac-Alq(3) and fac-Ir(ppy)(3) agree well with experimental data, whereas for the free-base porphyrin, naphthalene, and the polyacenes, the obtained quantum yields significantly differ from the experimental values, because the FC and adiabatic approximations are not accurate for these molecules.
Subject: ELECTRONIC-STRUCTURE CALCULATIONS
PHOTOPHYSICAL PROPERTIES
LUMINESCENCE CHARACTERISTICS
QUANTUM-CHEMISTRY
ENERGY-TRANSFER
EMISSION BANDS
MOLECULES
FLUORESCENCE
COMPLEXES
SPECTRA
114 Physical sciences
116 Chemical sciences
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