Improved Synthesis of 4,4′-Disubstituted-2,2′-Bipyridines

Abstract

Ruthenium(II) tris(2,2′-bipyridine) complexes show interesting photochemical properties^1. Complexes containing substituents in the 4-and 4′-position of the 2,2′-bipyridine ligand have recently been used in systems which are aimed at the conversion and storage of solar energy^2,3. 2,2′-Bipyridine has a long history as a metal-chelating agent⁴. The use of 4,4′-disubstituted bipyridines as metal-chelating agents so far has been restricted probably because the reported syntheses of these compounds are rather laborious and the yields are low or moderate^5–8.