Syntheses, crystal structures and solvatochromic properties of dinuclear oxalato-bridged copper(II) complexes

Three dinuclear copper(II) complexes, [Cu2(L1)2(μ-ox)](ClO4)2⋅2(CH3CN), [Cu2(L2)2(μ-ox)](ClO4)2⋅H2O, and [Cu2(L3)2(μ-ox)](ClO4)2 where ox = oxalato; L = N,N-dimethyl,N′-benzylethane-1,2-diamine, L1, N,N-diethyl,N′-benzylethane-1,2-diamine, L2, N,N-diisoprophyl,N′-benzylethane-1,2-diamine, L3, were prepared and characterized by elemental analyses, spectral (IR, UV–Vis) data and molar conductance measurements. The crystal structures of [Cu2(L1)2(μ-ox)](ClO4)2⋅2(CH3CN) and [Cu2(L3)2(μ-ox)](ClO4)2 have been determined by single-crystal X-ray analysis. Solvatochromic behaviors were investigated in various solvents, showing positive solvatochromism. The effect of steric hindrance around the copper ion imposed by N-alkyl groups of the diamine chelates on the solvatochromism property of the complexes is discussed. Solvatochromism was also studied with different solvent parameter models using stepwise multiple linear regression method.