Synthesis, characterization and laser flash photolysis studies of some naphthothiophenes bearing electron donor and acceptor functional groups

Photoinduced electron transfer processes have been investigated in a rigid naphthothiophene moiety which contains both electron donor (methoxy group, OCH3) and acceptor (dicyanovinyl or methoxycarbonyl group) functional groups at its two different ends. Both steady state absorption and fluorescence measurements coupled with the estimation of electronic coupling matrix elements, HDA, show the possibilities of occurrence of charge separation reactions within the donor and acceptor functional groups. Transient absorption measurements by laser flash photolysis technique using different delays in microsecond time domain demonstrate the presence of ion-pair in the triplet state and the stabilization of the radical ions within β-cyclodextrin (β CD) cavity against destructive charge recombination process. It appears that β CD microenvironment serves as the suitable medium to achieve one of the key requirements (enhancement of the survival duration of charge-separated species by retarding the charge recombination) for developing artificial photosynthetic device.