Stabilization of the Neutral [25]Hexaphyrin(1.0.1.0.1.0) Radical by Hetero‐Bimetal‐Coordination

Abstract

AbstractStabilization of hexaphyrin(1.0.1.0.1.0) (named “rosarin”) in its 25π radical state is achieved using a hetero‐bimetal‐coordination strategy. The antiaromatic BF2 complex B‐1 was first synthesized, and then rhodium ion was inserted into B‐1 to produce the BF2/Rh(CO)2 mixed complex Rh‐B‐1 as a highly air‐stable radical. The structures of B‐1 and Rh‐B‐1 were determined by single‐crystal X‐ray diffractions, and the antiaromatic or radical character was identified by various spectroscopy evidence and theoretical calculations. Rh‐B‐1 exhibits excellent redox properties, enabling amphoteric aromatic‐antiaromatic conversion to their 24/26π states. Compared to the 24/26π conjugation systems on the same skeleton, Rh‐B‐1 has the narrowest electrochemical and optical band gaps, with the longest absorption band at 1010 nm. The ring‐current analysis reveals intense paratropic currents for B‐1 and co‐existing diatropic‐paratropic currents for Rh‐B‐1. This hetero‐bimetal‐coordination system provides a novel platform for organic radical stabilization on porphyrinoids, showing the prospect of modulating ligand oxidation states through rational coordination design.