Photochemical studies of A2-E

Lipofuscin is thought to be involved in age-related macular degeneration as is one of its proposed components, an amphiphillic pyridinium-based bis-retinoid with a quaternary nitrogen atom, known as A2-E. We report the triplet state spectra obtained from photosensitisation using anthracene and 1-nitronaphthalene in benzene and methanol. The triplet state of A2-E has λmax at 550 nm and a lifetime of ∼30 μs, it is efficiently quenched by molecular oxygen with a second-order quenching rate constant of ∼1×109 dm3 mol−1 s−1. There is no significant triplet state formation from direct laser excitation of A2-E and hence its quantum yield of triplet state formation must be <0.01.