Intramolecular interactions and photoinduced electron transfer in isoalloxazine-naphthalene bichromophores

Abstract

The synthesis, the structural characterization and electrochemical and photophysical properties of new linear ( OFn) and macrocyclic ( MFn) bichromophoric systems containing one flavin and one naphthalene moiety, separated by (CH 2) n alkyl chains ( n = 4 or 6), are reported. The electrochemical properties of OF4, OF6, MF4, MF6 were investigated by cyclic voltammetry (CV) in ultra-dry THF and compared with the model compounds containing either the flavin unit ( FL6) or the monomethoxy- ( mona) and dimethoxy naphthalene ( dmona) derivatives, respectively. While only minor ground-state interactions were evidenced between the chromophores in the voltammetric curves and absorption spectra of bichromophores, luminescence data evidenced intramolecular photoinduced electron transfer processes as main deactivation routes of flavin-centered excited states. The rates of the intramolecular photoinduced electron transfer, involving the oxynaphthalene moieties as electron donors, were finally determined.