Coordination compounds of tetrazolate-5-carboxylate with cobalt(II): Synthesis, structure and magnetic properties

Four coordination compounds of tetrazolate-5-carboxylate (tzc) with cobalt(II), [Co2(tzc)2(H2O)6]·2H2O (1), [Co2(tzc)2(phen)2(H2O)2]·2H2O (2), [Co2(tzc)2(2,2′-bpy)2(H2O)2]·H2O (3), and [Co(tzc)(4,4′-bpy)] (4), where phen = 1,10-phenanthroline, 2,2′-bpy = 2,2′-bipyridyl, and 4,4′-bpy = 4,4′-bipyridyl, have been synthesized by the hydrothermal methods involving the in situ generation of the ligand from sodium ethyl tetrazolate-5-carboxylate. Compounds 1, 2 and 3 all contain dinuclear molecules in which metal ions are linked by the double N–N bridges from two tzc ligands in the μ2-N1,O1:N2 mode, and the dinuclear molecules are associated into 3D architecture through extensive hydrogen bonding and π–π stacking interactions in various fashions. Compound 4 exhibits a two-dimensional layer structure in which Co(tzc) chains with μ3-N1,O1:O1:N2 tzc are cross-linked by 4,4′-bpy. Magnetic investigations on 1–3 revealed intramolecular ferromagnetic coupling through the double N–N bridges with intermolecular ferromagnetic or antiferromagnetic interactions. The interaction through the mixed N–N and μ2-Ocarboxylate bridges in 4 is antiferromagnetic.