Three Ni/Co(II) complexes with 4,4′-bipyridine and benzoic acid derivatives as mixed coligands: Hydrothermal syntheses, structures, and magnetisms

Abstract

The hydrothermal reactions of 3,5-dinitrobenzoic acid, or p-toluic acid, 4,4′-bipyridine, with transition metal chlorides in basified solvent gave rise to three coordination polymers, [Ni 2(3,5-DNBC) 4(4,4′-bpy) 2(H 2O)] ( 1), [Co(3,5-DNBC) 2(4,4′-bpy) 2] ( 2), [Co 3(4,4′-bpy)( p-ToC) 6] ( 3), and characterized by elemental analysis, IR, single-crystal X-ray diffraction and variable-temperature magnetic measurements. Compound 1 crystallizes in the monoclinic system, P2 1/ c space group, the structure determination reveals that 1 has a 2D network based on lozenge grids, where each Ni II is in 4O + 2N coordination mode. Compound 2 is also monoclinic system, P2/ c space group, and the X-ray structural analysis shows that 2 also has a 2D network but based on rectangular grids with the Co II atom in a CoN 2O 4 environment. Compound 3 crystallizes in the triclinic system, P 1 ¯ space group, and polymerizes through nitrogen and oxygen atoms giving 1D chains with the Co II(1) atom in a CoO 6 environment and Co II(2) is in N + 4O coordination mode. In good agreement with the expected behavior, magnetic susceptibility measurements show weak ferromagnetic interactions for 1 and 3, whereas compound 2 exhibits moderate antiferromagnetic coupling.