X-ray crystal structures, electron paramagnetic resonance, and magnetic studies on strongly antiferromagnetically coupled mixed μ-hydroxide-μ-N1,N2-triazole-bridged one dimensional linear chain copper(II) complexes

Four new metal-organic polymeric complexes, [[Cu(mu-OH)(mu-ClPhtrz)][(H2O)(BF4)]}(n) (1), {[Cu(mu-OH)(mu-BrPhtrz))-[(H2O)(BF4)]}(n) (2), {[Cu(mu-OH)(mu-ClPhtrz)(H2O)](NO3)}(n) (3), and f{[Cu(mu-OH)(mu-BrPhtrz)(H2O)](NO3)}(n) (4) (ClPhtrz = N-[(E)-(4-chlorophenyl) methylidene]-4H-1,2,4-triazol-4-amine; BrPhtrz = N-[(E)-(4-bromophenyl)methylidenel-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 N-1,N-2-1,2,4-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[Sigma S-i.Si+1]). The nature and the magnitude of the antiferromagnetic exchange were discussed on the basis of complementarity/countercomplementarity of the two competing bridges.