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QUANTUM MECHANICAL ANALYSIS OF ELECTRONIC TRANSITIONS IN SOME CYANINE DYE PHOTOSENSITIZERS
Author(s) -
Weinstein Harel,
Apfelderfer Benzion,
Berg Robert A.
Publication year - 1973
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.1751-1097.1973.tb06409.x
Subject(s) - cyanine , cndo/2 , redistribution (election) , chemistry , atomic electron transition , ion , ionization , molecular orbital , atomic physics , atomic orbital , ionization energy , electron , conjugated system , molecule , physics , organic chemistry , polymer , quantum mechanics , astronomy , politics , political science , law , fluorescence , spectral line
— INDO and CNDO/2 calculations of some cyanine dye photosensitizers are reported. The redistribution of electron charge density following various electronic transitions is analyzed and found to be localized mainly in the conjugated chains. The charge redistribution is shown to be strongly influenced by presence of the counter ion, which also proves to be a main factor in determination of the ionization energy values and symmetry of the molecular orbitals. The results suggest an ionization process different from the one considered in previous approaches, because the electron is shown here to leave the negative ion, with the conjugated cation acting as a “photon trap”. This situation is shown to provide a link between different models of optical sensitization. Results and assumptions from other methods, including the ‘electron gas’ models for the conjugated chain, are discussed in view of the counter‐ion effect and the chain–localized transitions found here.