First-principles calculations of anharmonic and deuteration effects on the photophysical properties of polyacenes and porphyrinoids

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Valiev , R R , Nasibullin , R T , Cherepanov , V N , Baryshnikov , G , Sundholm , D , Ågren , H , Minaev , B F & Kurten , T 2020 , ' First-principles calculations of anharmonic and deuteration effects on the photophysical properties of polyacenes and porphyrinoids ' , Physical Chemistry Chemical Physics , vol. 22 , no. 39 , pp. 22314-22323 . https://doi.org/10.1039/d0cp03231j

Title: First-principles calculations of anharmonic and deuteration effects on the photophysical properties of polyacenes and porphyrinoids
Author: Valiev, R. R.; Nasibullin, R. T.; Cherepanov, V. N.; Baryshnikov, G.; Sundholm, D.; Ågren, H.; Minaev, B. F.; Kurten, T.
Contributor: University of Helsinki, Department of Chemistry
University of Helsinki, Department of Chemistry
University of Helsinki, Department of Chemistry
Date: 2020-10-21
Language: eng
Number of pages: 10
Belongs to series: Physical Chemistry Chemical Physics
ISSN: 1463-9076
URI: http://hdl.handle.net/10138/334017
Abstract: A new method for calculating internal conversion rate constants (k_(IC)), including anharmonic effects and using the Lagrangian multiplier technique, is proposed. The deuteration effect on k_(IC) is investigated for naphthalene, anthracene, free-base porphyrin (H2P) and tetraphenylporphyrin (H2TPP). The results show that anharmonic effects are important when calculating k_(IC) for transitions between electronic states that are energetically separated (Delta E) by more than 20 000-25 000 cm(-1). Anharmonic effects are also important when Delta E <20 000-25 000 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 S-1 and S-2 states of naphthalene induced by non-adiabatic interactions. The non-adiabatic interaction matrix element between the S-1 and S-2 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_(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.
Subject: RADIATIONLESS ELECTRONIC-TRANSITIONS
MORSE OSCILLATOR MODEL
INTERNAL-CONVERSION
SPIN-ORBIT
ORGANIC-MOLECULES
MATRIX-ELEMENTS
RATE CONSTANTS
FLUORESCENCE
COMPLEX
RATES
116 Chemical sciences
114 Physical sciences
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