Zheng RH, Wei WM, Yan YM. Theoretical study on resonance Raman spectra of meso-tetrakis(3,5-di-tertiarybutylphenyl)-porphyrin due to the second-order Herzberg-Teller mechanism.
Spectrochim Acta A Mol Biomol Spectrosc 2020;
241:118659. [PMID:
32652289 DOI:
10.1016/j.saa.2020.118659]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Revised: 06/19/2020] [Accepted: 06/27/2020] [Indexed: 06/11/2023]
Abstract
Using quantum chemistry computations TDDFT//B3LYP/6-31G(d), we study resonance Raman spectra of the Q band for meso-tetrakis(3,5-di-tertiarybutylphenyl)-porphyrin (H2TBPP) molecule due to the Franck-Condon and non-Condon mechanisms including the Herzberg-Teller and second-order Herzberg-Teller terms. Generally, the Herzberg-Teller terms are large. However, for some vibrational modes, the second-order Herzberg-Teller terms are the strongest and dominate resonance Raman spectra, which may also impact on fluorescence and absorption spectra. Hence, the Taylor expansion of the electric dipole transition moment with respect to the normal coordinates at the equilibrium structure of the ground electronic state may not converge for H2TBPP. A method to solve this problem is suggested.
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