Coordination compounds of cobalt(II), nickel(II), and copper(II) with 4-(3-hydroxyphenyl)-1,2,4-triazole: Synthesis and study

New Co(II), Ni(II), and Cu(II) complexes with 4-(3-hydroxyphenyl)-1,2,4-triazole (L) with the compositions [Co3L6(H2O)5(C2H5OH)](NO3)6 · 2H2O · C2H5OH (I), [Ni3L6(H2O)6](NO3)6 · 2H2O (II), and [M3L6(H2O)6](ClO4)6 · nH2O (M = Co2+, n = 2 (III); Ni2+, n = 2 (IV); Cu2+, n = 0 (V)) are synthesized. The complexes are studied by X-ray structure analysis, X-ray diffraction analysis, UV and IR spectroscopy, and the statistical magnetic susceptibility method. All compounds have the linear trinuclear structure. Ligand L is coordinated to the metal ions by the N(1) and N(2) atoms of the heterocycle according to the bidentate bridging mode. In all compounds the coordination polyhedron of the metal atom is a distorted octahedron. The molecular and crystal structures of compound I, [Co3L6(H2O)6](ClO4)6 · 8C2H5OH (IIIa), and [Ni3L6(H2O)6](ClO4)6 · 8C2H5OH (IVa) are determined.