PHOTOINITIATED ELECTRON-TRANSFER INTERACTION OF ALL-TRANS RETINAL WITH ELECTRON-DONORS AND ACCEPTORS

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