Axially substituted phosphorous(v) corrole with polycyclic aromatic hydrocarbons: syntheses, X-ray structures, and photoinduced energy and electron transfer studies

Abstract

Phosphorous(V) corrole has been employed to build stable, donor–acceptor complexes capable of undergoing photoinduced energy and electron transfer events. Two triads, the first one with naphthalene axial entities (Triad 1) and the second one with pyrene axial entities (Triad 2), were newly synthesized for this purpose. The X-ray structure of Triad 1 revealed the presence of two naphthalene entities bound to the phosphorous centre without causing steric crowding. The electrochemical and computational studies revealed the electron deficient nature of the phosphorous corrole in the triads. Excited state events, monitored by both time-resolved emission and transient absorption studies, revealed several interesting results. In the case of Triad 1, efficient energy transfer from singlet excited naphthalene to corrole was observed, however, no photo events from excited phosphorous corrole were evident. Interestingly, in the case of Triad 2, although an energy transfer process from singlet excited pyrene to corrole was weak, evidence of photoinduced charge separation leading to the formation of pyrene˙⁺-PC˙⁻ was witnessed from femtosecond transient absorption studies when either pyrene or corrole was selectively excited. The importance of axial bound donor entities on phosphorous(V) corrole in promoting photoinduced energy and electron transfer events is borne out from the present study.