[Photophysics of complex formations between chlorophyll a and its analogs with pi acceptors]

Efficient quenching of fluorescence was shown to proceed in the complexes of chlorophyll a and its analogs with tetracyanochinodimethane (TCD), 1,3,5-trinitrobenzene (TNB), m-dinitrobenzene (DNB) and n-benzoquinone. In chlorophyll a--TCD and--DNB complexes quenching is characterized by the rate constant approximately greater than 5 x 10(10) s-1, and in chlorophyll a--n-benzoquinone greater approximately than 5 x 10(9) s-1. Possible ways of desactivation of singlet-excited state of chlorophyll a in the complexes with TCD and TNB were analysed. No triplet states of chlorophyll a complexes with TCD and TNB and no cation-radicals were recorded. It is suggested that efficient desactivation of the pigment singlet-excited state may be explained by a reversible phototransfer of the electron.