Premium
PHOTOPHYSICAL PROPERTIES OF 3,3′‐DIALKYLTHIACARBOCYANINE DYES IN HOMOGENEOUS SOLUTION
Author(s) -
Krieg Marianne,
Redmond Robert W.
Publication year - 1993
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.1751-1097.1993.tb02321.x
Subject(s) - photochemistry , photoisomerization , chemistry , quantum yield , intersystem crossing , microsecond , singlet oxygen , singlet state , fluorescence , triplet state , alkyl , excited state , quenching (fluorescence) , oxygen , isomerization , catalysis , organic chemistry , molecule , physics , quantum mechanics , nuclear physics , astronomy
The photophysical properties of 3,3′‐dialkylthiacarbocyanine iodides and chlorides were measured in various solvents. It was found that photoisomerization and fluorescence are the major contributors to the deactivation of the excited singlet state; intersystem crossing occurs with only a very low efficiency. In ethanol, a triplet yield of 0.004 and a singlet oxygen quantum yield of 0.002 were determined. The photophysical parameters of these dyes are not substantially influenced by the length of the alkyl chain or the size of the halide counterion. The substitution of an ethyl with an octadecyl‐chain only slightly hinders photoisomerization, and the replacement of the chloride with an iodide reduces only marginally the fluorescence lifetimes and fluorescence quantum yields in chloroform. A significant external heavy‐atom effect is observed using dibromoethane as a solvent: triplet and singlet oxygen yields increase7–10‐fold, and the triplet lifetime decreases from 55 μs to 15 mUs.