Synthesis and spectral property study of porphyrin-anthraquinone dyads bonded through azo

Abstract

To determine if the dihedral angle between the phenyl group and the porphyrin ring in the meso-phenyl porphyrin (H2TPP) could be adjusted by selective substitution of the naphthyl group for phenyl groups, novel dyads with a free-base porphyrin donor and anthraquinone acceptor linked by a rigid azo bond were synthesized and their spectral properties were investigated in detail. The Soret absorption band of dyads with meso-naphthyl groups in porphyrin shows 5–7 nm red shift as compared to the corresponding raw materials due to the introduction of the anthraquinone moiety. Fluorescence from the porphyrin moiety was found to be intensely quenched with the addition of anthraquinone moiety in the dyads; the highest quenching rate was observed to be 95% in the dyad prepared by meso-tetranaphthyl porphyrin. This indicates that the efficiency of the intramolecular photoinduced electron transfer in porphyrin-anthraquinone dyads could be changed by substituting the meso-phenyl group in porphyrin for the meso-naphthyl group.