Synthesis and structure of di-μ-bromo-bis[(1,5-dimethyl-6-oxo-3-(2-pyridyl)verdazyl)copper(I)]

Reaction of the verdazyl precursor 1,4,5,6-tetrahydro-2,4-dimethyl-6-(2'-pyridyl)-1,2,4,5-tetrazin-3(2H)-one (pvdH(3)) with oxygen and copper(I) bromide in acetonitrile results in precipitation of the crystalline diradical di-mu-bromo-bis[(1,5-dimethyl-6-oxo-3-(2-pyridyl)verdazyl)copper(I)]. The solid shows a slightly anisotropic ESR spectrum and magnetic susceptibility measurements indicate weak antiferromagnetic exchange between the free radicals, consistent with the assignment as a copper(I) ion coordinated to a free radical.