Structural, solvatochromism and magnetic properties of two halogen bridged dinuclear copper (II) complexes: A density functional study

Abstract

Abstract Two dinuclear copper(II) complexes [Cu(μ-Cl)(L)Cl] 2 , 1, [Cu(μ-Br)(L)Br] 2 , 2 , where L is N,N -dimethyl, N΄ -benzyl-ethylenediamine were synthesized and structurally characterized crystallographically and spectroscopically. Single crystal X-ray diffraction study demonstrated that in dinuclear complexes the copper(II) centers are in linked by two halo bridges. The geometry around the copper ions in 1 is square pyramidal (τ = 0.068) and in 2 is an intermediate between a trigonal bipyramidal and square pyramid (τ = 0.498). The magnetic coupling constants ( J and zJ' ) of the compounds have been derived by appropriate fitting of the experimentally measured molar susceptibility variation with the temperature. The results of the measurements showed that two copper(II) centers are ferromagnetically coupled with J = 5.0 cm −1 for 1 and J = 15.1 cm −1 for 2 through halo bridges and antiferromagnetically coupled via interdimer interaction ( zJ′ = −0.9 cm −1 for 1 and zJ′ = −2.9 cm −1 for 2 ). The origin of intra- and interdimer interactions and the magnitude of the magnetic coupling have been analyzed by means of density functional theory within broken–symmetry (BS) framework. Theoretical calculations of the exchange coupling confirm the experimental results (yielding values of J = 0.81 cm −1 for 1 and J = 10.51 cm −1 for 2 and J ′= −0.1 cm −1 for 1 and J′ = −0.56 cm −1 for 2 ). The solvatochromic property of the complexes was investigated and it was found that this phenomenon is due to structural changes of the complexes in solution.