Mixed azide and 5-(pyrimidyl)tetrazole bridged Co(II)/Mn(II) polymers: synthesis, crystal structures, ferroelectric and magnetic behavior.

The reaction of pyrimidine-2-carbonitrile, NaN(3) in the presence of Co(NO(3))(2)·6H(2)O or MnCl(2)·4H(2)O leads to the formation of complexes [Co(pmtz)(μ(1,3)-N(3))(H(2)O)](n) (1) and [Mn(pmtz)(μ(1,3)-N(3))(H(2)O)](n) (2) respectively, under hydrothermal condition [pmtz = 5-(pyrimidyl)tetrazolate]. These two complexes have been fully characterized by single crystal X-ray diffraction. Complex 1 crystallizes in a non-centrosymmetric space group Aba2 in the orthorhombic system and is found to exhibit ferroelectric behavior, whereas complex 2 crystallizes in the P2(1)/c space group in the monoclinic system. Variable temperature magnetic characterizations in the temperature range of 2-300 K indicate that complex 1 is a canted antiferromagnet (weak ferromagnet) with T(c) = 15.9 K. Complex 1 represents a unique example of a multiferroic coordination polymer containing tetrazole as a co-ligand. Complex 2 is a one-dimensional chain of Mn(II) bridged by a well-known antiferromagnetic coupler end-to-end azido ligand. In contrast to the role played by the end-to-end azido pathway in most of the transition metal complexes, complex 2 showed unusual ferromagnetic behavior below 40 K because of spin canting.