TRIPLET-STATE PHOTOPHYSICAL PROPERTIES AND INTERSYSTEM CROSSING QUANTUM EFFICIENCIES OF HOMOLOGS OF RETINALS IN VARIOUS SOLVENTS

Employing the techniques of pulse radiolysis and nitrogen laser flash photolysis, several photophysical properties of the lowest triplet states of a series of polyenals related to retinals as homologues have been studied in various polar and nonpolar solvents. The series includes two polyenals not heretofore studied, an all-trans 17-carbon homologue (shorter than retinal by one double bond) and an all-trans 24-carbon homologue (longer than retinal by two double bonds). The former polyenal has high quantum efficiencies of occupation of the lowest triplet (ΦT1) in both polar and nonpolar solvents and the latter polyenal has very low ΦT1values in any solvent. The results are discussed in relation to the state order as a function of chain length along the series in general and as a function of the nature of the solvent in the case of certain specific members. © 1979, American Chemical Society. All rights reserved.