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

A tetranuclear 'stepped wise' copper(II) complex, [Cu-4(mu(2)-OH)(2)(mu(3)-OH)(2)(2,2'-bipy)(4)Cl-2]Cl-2.6H(2)O 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 (mu-2) as well as tridentate (mu-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 = - J(1)(S1S2 + S3S4)-J(2)(S1S4)-J(3)(S1S3 + S2S4) and the best fit parameters, assuming the g factors are identical and J(2) = J(3), leads to J(1) = 22.71 cm(-2) = J(2) = J(3), 0.34 cm(-1) and g = 2.10. The magnetic results are interpreted with structural parameters. (C) 2003 Elsevier Science Ltd. All rights reserved.