Preparation, properties, and X-ray structures of 5,5′-bi(8-aminoquinoxalyl)s: novel Wurster-type electron donors with a heterobiaryl skeleton

The title electron donors were prepared by the double condensation reactions of 2,2′,3,3′-tetraamino-4,4′-bis(1-pyrrolidinyl)biphenyl with 1,2-diketones. They adopt twisted conformations in crystal, yet the reversible two-stage one-electron oxidation process suggests the planar geometries for the oxidized species. Depending on the nature of substituents on the pyrazine ring, this π-system can be endowed additional features such as chiroptical properties or metal coordination ability.