Photoinitiated electron transfer interaction of all-trans retinal with electron donors and acceptors

Formation of radical ions of all-trans retinal (ATR) has been demonstrated using H-1 CIDNP on its photoinitiated interaction with electron donor (stilbene) and accepters (2,5-dichlorobenzoquinone, chloranil). CIDNP data show qualitative agreement with calculations of spin density distribution in ATR radical ions conducted by means of the INDO/AM1 method. It has been found that CIDNP effects are formed in the reaction of reversible electron transfer between ATR and either electron donors or accepters. Retinal isomers arising under irradiation also give rise to nonequilibrium population of spin states in NMR spectra. The correlation between CIDNP effects and the processes of cis-trans isomerization has been discussed. (C) 1997 Elsevier Science S.A.