Magneto structural correlations of a ‘stepped-wise’ discrete tetranuclear unit of copper(II), [Cu₄(µ₂-OH)₂((µ₃-OH)₂(2,2′-bipy)₄Cl₂]Cl₂·6H₂O

Abstract

A tetranuclear ‘stepped wise’ copper(II) complex, [Cu₄(μ₂-OH)₂(μ₃-OH)₂(2,2′-bipy)₄Cl₂]Cl₂·6H₂O has been synthesized and the crystal structure of the complex redetermined. The magnetic behavior has been investigated in the temperature range 300–4.2 K based on its novel binding modes of the OH−, i.e. OH− anions bridge the copper(II) centers in a bidentate (μ-2) as well as tridentate (μ-3) fashion and this shows ferromagnetic interactions. The fit of the experimental data was made by the irreducible tensor operator formalism (ITO) using the clumag program based on the Hamiltonian; H=−J1(S1S2+S3S4)−J2(S1S4)−J3(S1S3+S2S4) and the best fit parameters, assuming the g factors are identical and J2=J3, leads to J1=22.71 cm^-1; J2=J3=0.34 cm^-1 and g=2.10. The magnetic results are interpreted with structural parameters. A novel tetranuclear copper(II) complex, [Cu₄(μ₂-OH)₂(μ₃-OH)₂(2,2′-bipy)₄Cl₂]Cl₂·6H₂O has been synthesized. This is the rare type of copper(II) complex having discrete tetranuclear Cu₄(II)O₄ entities with a ‘stepped-wise’ structure. A novel feature of the title complex is that the OH^- anion functions as a bridging bidentate (μ-2) and tridentate (μ-3). The magnetic behavior has been investigated in the temperature range 300–4.2 K and shows ferromagnetic interactions.