Coordination chemistry of tetrazolate-5-carboxylate with manganese(II): synthesis, structure and magnetism

Six Mn(II) coordination compounds with tetrazolate-5-carboxylate (tzc), have been synthesized and characterized. They are of the formula [Mn2(tzc)2(H2O)2].4H2O (), Mn(tzc)(H2O)2 (), [Mn2(tzc)2(phen)2(H2O)2] (), [Mn(tzc)(2,2'-bpy)(H2O)2] (), [Mn(tzc)(4,4'-bpy)] () and [Mn2(tzc)2(H2O)2].(bpp) (), where phen=1,10-phenanthroline, 2,2'-bpy=2,2'-bipyridyl, 4,4'-bpy=4,4'-bipyridyl, and bpp=1,3-di(4-pyridyl)propane. Versatile coordination modes of the tzc ligand have been recognized in these compounds. In the absence of auxiliary ligands, a dinuclear compound () with the Mn2(N-N)2 moiety and a 1D coordination polymer () consisting of two types of disordered Mn(tzc) chains have been obtained at different temperatures. The incorporation of chelating auxiliary ligands (2,2'-bpy and phen) leads to a mononuclear () and a dinuclear () compounds, the structure of the latter resembling that of . The use of the ditopic auxiliary ligand 4,4'-bpy gives a 2D coordination polymer () in which disordered Mn(tzc) chains are cross-linked by 4,4'-bpy. However, the potentially ditopic ligand bpp is not involved in coordination but serves as hydrogen-bonded bridge between the Mn(tzc) chains to give compound . Magnetic investigations suggest that the double N-N bridges in the dinuclear compounds ( and ) mediate weak ferromagnetic coupling. However, in compounds and , which consist of 1D disordered Mn(tzc) chains with different bridging moieties, the intra-chain interactions are dominated by antiferromagnetic coupling.