Copper(II) and Cobalt(II) Carboxylates Containing the 1,3,4-Oxadiazole Fragment: Structures and Properties

Abstract Complexes [Сu 2 L 4 (MeOH) 2 ] ( I ) and [СoL 2 ] ( II ) are synthesized by the reactions of copper(II) and cobalt(II) acetates with 3-[5- p -tolyl)-1,3,4-oxadiazol-2-yl]acrylic acid (HL). The crystal structure of complex I is determined by X-ray diffraction (XRD) (CIF file CCDC no. 2052347). The crystals are monoclinic, space group C 2/ c , a = 26.056(4), b = 19.677(3), c = 13.998(2) Å, β = 91.571(3)°, V = 7175(2) Å 3 , ρ calc  = 1.026 g/cm 3 , Z = 4. In a molecule of complex I , the pair of centrosymmetric copper atoms is bound by four bridging carboxyl groups. The intramolecular Cu…Cu distance is 2.654(2) Å. The coordination polyhedron CuO 5 is a distorted square pyramid. The magnetic interactions between the copper(II) ions in complex I are shown to be antiferromagnetic (2 J = –185 cm –1 ). In the case of complex II , the application of an external magnetic field decreases the magnetic relaxation rate. The Raman mechanism and direct mechanism are the most probable route for magnetization relaxation. Unlike the copper(II) complex, complex II is probably mononuclear in both the solution and solid phase.