Abstract
Core-modified isophlorin-metal complexes were successfully prepared by redox-coupled complexation of P,S,N₂-hybrid porphyrin with zerovalent palladium, nickel, and platinum. In this transformation, the core-phosphorus atom plays crucial roles in enhancing the electron-accepting ability of the 18pi porphyrin ring and stabilizing the 20pi isophlorin ring owing to high P-M affinity. The isolated Pd and Pt complexes are chemically stable under ambient conditions. The Pd-P,S,N₂ isophlorin complex was structurally characterized by X-ray crystallography, which revealed a distorted 20pi plane with a square planar palladium(II) center. Experimental (¹H, UV-vis, and X-ray) and theoretical (density functional theory calculations) results suggest that the P,S,N₂-isophlorin-metal complexes possess nonaromaticity in terms of both magnetic and geometrical criteria.