Enhancement of photoisomerization of polymethine dyes in complexes with biomacromolecules

Photochemical processes (photoisomerization and generation of the triplet state) of the thiacarbocyanine dyes 3,3′,9-trimethylthiacarbocyanine iodide (Cyan 2), 3,3′-diethyl-9-methylthiacarbocyanine iodide (DMTC), and 3,3′,9-triethylthiacarbocyanine iodide (TETC) in complexes with biomacromolecules—DNA and chondroitin-4-sulfate—were studied by flash photolysis. It has been shown that, along with generation of the triplet state, enhancement of the photoisomer formation is observed for Cyan 2 and DMTC complexed with the biomolecules. This effect can be explained by the influence of the biopolymer matrix on the potential energy curves of the photoisomerization process.