Redox‐Active Guanidine Ligands with Pyridine and <i>p</i>‐Benzoquinone Backbones

Abstract

Abstract Herein we report on the synthesis and some aspects of the chemistry of the new redox‐active ligands 2,3,5,6‐tetrakis(tetramethylguanidino)pyridine, 2,3,5,6‐tetrakis(tetramethylguanidino)‐ p ‐benzoquinone and 2,3,5,6‐tetrakis( N , N′ ‐dimethyl‐ N , N′ ‐ethyleneguanidino)‐ p ‐benzoquinone. All three ligands are strong electron donors. In addition, the p ‐benzoquinone systems feature low LUMO energies and small HOMO–LUMO gaps. A comparison of the ligands was made with regard to their optical properties, Brønsted basicity and electron‐donor properties; results of quantum chemical calculations were included in this comparison. Subsequently, dinuclear copper complexes were prepared. Preliminary experiments on their redox chemistry followed.