Synthesis, crystal structures, spectral and magnetic properties of nickel(II) pyridinecarboxylates with N-heterocyclic ligands

The synthesis and characterization of eight new pseudooctahedral nickel(II) aqua-complexes [Ni(2-MeSnic)(2)(L)(2)(H2O)(2)] (where 2-MeSnic is 2-methylsulfanylnicotinato and L is furo[3,2-c] pyridine - fpy, 2,3-dimethyl-furo[3,2-c] pyridine -Me2fpy, 2-(3-trifluoromethylphenyl)-furo[3,2-c] pyridine -CF(3)Phfpy, 3,5-dimethylpyridine - 3,5-Me(2)py and iso-quinoline - iq) as well as complexes [Ni(2-MeSnic)(2)(L)(2)] (where L is 2-methylfuro[3,2-c] pyridine -Mefpy), benzo[4,5] furo[3,2-c] pyridine - Bfpy and iso-quinoline - iq) are reported. Crystal structure of complexes [Ni(2-MeSnic)(2)(L)(2)(H2O)(2)] (L = fpy and Me2py) was determined by the single-crystal X-ray structure analysis and that of [Ni(2-MeSnic)(2)(L)(2)(H2O)(2)] (L = Me-2 fpy and iq) complexes was determined using X-ray powder diffraction data. The Ni(II) central atom in all four complexes is situated at the centre of symmetry and it is pseudooctahedrally coordinated by two carboxylato oxygen atoms of the unidentate 2-methylthionicotinato ligands, the two pyridine nitrogen atoms of unidentate L, and two oxygen atoms of aqua ligands. The hydrogen atoms of aqua ligands in all four cases form hydrogen bonds. The IR and electronic data of complexes without aqua ligands [Ni(2-MeSnic)(2)L-2] (L = Mefpy, Bfpy and iq) are rather typical for asymmetrically chelating carboxylic groups, unidentate L, as well as pseudooctahedral nickel(II) atoms. Magnetic measurements of [Ni(2MeSnic)(2)(fpy)(2)(H2O)(2)], [Ni(2-MeSnic)(2)(3,5-Me2py)(2)(H2O)(2)] and [Ni(pydc)(pydm)]center dot H2O (where pydc is pyridine-2,6-dicarboxylate and pydm is pyridine-2,6-dimethanol) revealed that they behave magnetically as typical S = 1 spin systems with large zero-field splitting. These compounds match well and to some extend the range of the magnetostructural D-correlation for hexacoordinate Ni(II) complexes with rather high structural and magnetic anisotropy. (C) 2015 Elsevier B.V. All rights reserved.