Synthesis and solvatochromism studies of new mixed-chelate dinuclear copper(II) complexes with different counter ions

摘要

Four new symmetric mixed-chelate dinuclear complexes type [Cu _2(L)_2(TAE)]X_2, where TAE = tetraacetylethane; L = N,N-dimethyl-N′-benzylethylenediamine (L~1) or N,N′-dibenylethylenediamine (L~2); X = ClO_4 or BPh_4 have been synthesized and characterized on the bases of elemental analysis, spectroscopic and conductance measurements. The X-ray crystal analysis of [Cu_2(L~1)_2(TAE)](ClO _4)_2 demonstrated that the two copper(II) ions are not equivalent. The axial position of the first copper is occupied by a ClO _4~- ion with a square pyramidal geometry whereas; the second copper ion resides in an octahedral environment determined by two perchlorate anions. However, in solution, the perchlorate ions are driven out by solvent molecules leading to their solvatochromism. The solvatochromism of the complexes were investigated in various organic solvents and also were compared with those of the corresponding mononuclear complexes [Cu(L)(acac)]ClO _4. Their solvatochromism were also investigated with different solvent parameters models using stepwise multiple linear regression (SMLR) method. The results suggested that the DN parameter of the solvent has the dominate contribution to the shift of the d-d absorption band of the complexes. The results demonstrated that the complexes with counter ions of BPh_4 are more solvatochromic in very weak donor solvents owing to their disinclination in ion-pair formation.