Photosensitizers: comprehensive photophysics/photochemistry and theory of coumarins, chromones, their homologues and thione analogues

Abstract

The photophysical–photochemical behaviour, including absorption spectra, fluorescence spectra and lifetimes, phosphorescence spectra, triplet–triplet transient spectra, triplet lifetimes and quantum yields and sensitized singlet oxygen formation and yields, has been determined for many of a group of 22 carbonyl and thione compounds. These include coumarins, psoralens, chromones and furochromone and their thiones. Many of the thiones were synthesized for the first time. Two types of theoretical calculations were carried out on the majority of the compounds. The principal goals of the research for the thiones, were (1) to produce or improve the photosensitizer capabilty of the compounds in vivo, (2) to shift the spectra of the compounds to significantly longer wavelength and (3) to increase the triplet and singlet oxygen quantum yields. Most of these have been largely achieved. The photosensitizing abilities of two of the thiones have been evaluated using a unique testing technique employing a series of genetically engineered bacteria.