An electron acceptor moiety based on the 4,5-dinitro-1,8-naphthalenedicarboximide system has been prepared and used as the basis for synthesis of a porphyrin - imide dyad (P-NIm) and a carotenoid - porphyrin - imide triad molecule (C-P-NIm). Excitation of the porphyrin moiety in either compound with visible light leads to rapid photoinduced electron transfer to generate in high yield a charge-separated state consisting of the porphyrin radical cation and imide radical anion. In the triad, this C-P•+-NIm•- state decays in part by a second electron transfer from the carotenoid to yield a final C•+-P-NIm•- charge-separated state. In benzonitrile, this state is formed with a quantum yield of 0.33 and has a lifetime of 430 ns. The 4,5-dinitro1,8-naphthalenedicarboximide moiety is conveniently synthesized and undergoes facile and reversible one-electron reduction. The NIm•- ion has a readily observable spectroscopic signature in the visible. In contrast to a series of closely related triads reported by other investigators, the triad studied here shows no evidence for photoinduced electron transfer from the carotenoid first excited singlet state.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films
- Materials Chemistry