Azide-bridged copper(II) and manganese(II) compounds with a zwitterionic tetrazolate ligand: Structures and magnetic properties

Two azide-bridged coordination polymers, [Cu(mptz)(N₃) ₂] (1) and [Mn(mptz)(N₃)₂H₂O] (2), (mptz = N-methyl-4-pyridinium tetrazolate), were synthesized and crystallographically and magnetically characterized. Compound 1 is a neutral 1D coordination polymer in which the Cu^II ions, which are in a square pyramidal surrounding, are linked by double end-on azide bridges in an alternating basal-basal and basal-apical fashion. Compound 2 exhibits a 3D Mn^II-azide coordination framework with the (10,3)-b net topology, in which the double end-on-azide-bridged dimanganese units are interlinked by single end-to-end azide bridges. The magnetic analyses indicated that 1 behaves magnetically as a quasi-dimer with an S = 1 ground state due to a strong ferromagnetic interaction through the basal-basal azide bridges and a very weak antiferromagnetic coupling through the basal-apical azide bridges. Compound 2 exhibits 3D antiferromagnetic behaviors with T_N = 24.0 K, where the end-to-end and end-on azide bridges mediate the antiferromagnetic and ferromagnetic interactions, respectively. A pyridinium tetrazolate zwitterion as an auxiliary ligand led to two coordination compounds that have different azide-bridging networks. The 1D Cu^II compound magnetically behaves as a ferromagnetic quasi-dimer, while the Mn^II compound behaves as a 3D antiferromagnet.