X-ray Crystal Structures, Electron Paramagnetic Resonance, and Magnetic Studies on Strongly Antiferromagnetically Coupled Mixed μ-Hydroxide-μ-<i>N</i>¹,<i>N</i>²-Triazole-Bridged One Dimensional Linear Chain Copper(II) Complexes

Four new metal-organic polymeric complexes, {[Cu(μ-OH)(μ-ClPhtrz)][(H2O)(BF4)]}n (1), {[Cu(μ-OH)(μ-BrPhtrz)][(H2O)(BF4)]}n (2), {[Cu(μ-OH)(μ-ClPhtrz)(H2O)](NO3)}n (3), and {[Cu(μ-OH)(μ-BrPhtrz)(H2O)](NO3)}n (4) (ClPhtrz = N-[(E)-(4-chlorophenyl)methylidene]-4H-1,2,4-triazol-4-amine; BrPhtrz = N-[(E)-(4-bromophenyl)methylidene]-4H-1,2,4-triazol-4-amine), were synthesized in a reaction of substituted 1,2,4-triazole and various copper(II) salts in water/acetonitrile solutions. The structures of 1−4 were characterized by single-crystal X-ray diffraction analysis. The Cu(II) ions are linked both by single N1,N2-1,2,4-triazole and hydroxide bridges yielding one dimensional (1D) linear chain polymers. The tetragonally distorted octahedral geometry of copper atoms is completed alternately by two water and two BF4− anion molecules in 1 and 2 but solely by two water molecules in 3 and 4. Magnetic properties of all complexes were studied by variable temperature magnetic susceptibility measurements. The Cu(II) ions are strongly antiferromagnetically coupled with J = −419(1) cm−1 (1), −412(2) cm−1 (2), −391(3) cm−1 (3), and −608(2) cm−1 (4) (based on the Hamiltonian H = −J[∑Si·Si+1]). The nature and the magnitude of the antiferromagnetic exchange were discussed on the basis of complementarity/countercomplementarity of the two competing bridges.