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STEREOELECTRONIC PROPERTIES OF PHOTOSYNTHETIC AND RELATED SYSTEMS—VIII. AB INITIO QUANTUM MECHANICAL CHARACTERIZATION OF THE ELECTRONIC STRUCTURE AND SPECTRUM OF THE BACTERIOPHEOPHORBIDE a ANION RADICAL
Author(s) -
Petke J. D.,
Maggiora Gerald M.,
Shipman Lester L.,
Christoffersen Ralph E.
Publication year - 1980
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1980.tb04036.x
Subject(s) - excited state , ab initio , oscillator strength , absorption spectroscopy , ground state , atomic physics , chemistry , ion , molecular electronic transition , configuration interaction , wave function , absorption (acoustics) , ab initio quantum chemistry methods , electronic structure , physics , spectral line , computational chemistry , molecule , quantum mechanics , organic chemistry , acoustics
— Ab initio configuration interaction wavefunctions and energies are reported for 16 doublet states of the anion radical of ethyl bacteriopheophorbide a (Et‐BPheo a ‐˙ ), and are employed in an analysis of the electronic absorption spectrum. The lowest excited doublet state D 1 is predicted to lie 8601 cm ‐1 above the ground state D 0 ; the D 1 ← D 0 transition is nearly forbidden, with a computed oscillator strength f = 0.002. The visible absorption spectrum is shown to consist of transitions to three 2 (π, π*) states, D 2 , D 3 , and D 4 . The D 4 ← D 0 transition (y‐polarized, f = 0.91) appears to account for observed intense absorption at 15 800 cm ‐1 . The Soret band of Et‐BPheo a ‐˙ is shown to consist of transitions to several 2 (π,π*) states, D 7 ‐D 15 . Transitions of particularly high intensity include D 7 ← D 0 (y‐polarized, f = 0.72), D 10 ← D 0 (y‐polarized, f = 1.1), D 12 ← D 0 (xy‐polarized, f = 0.86) and D 15 ← D 0 (y‐polarized, f = 0.83). Spin density data and plots are used to describe and compare the general features of the unpaired spin distributions in D 0 and D 1 , which are in reasonable agreement with other reported calculated values and available experimental data for D 0 .