Syntheses and characterization of mixed-chelate copper(II) complexes containing different counter ions; spectroscopic studies on solvatochromic properties

Solvatochromic mixed-chelate copper(II) complexes, [Cu(Cl-acac)(diamine)]X (where Cl-acac = 3-chloroacetylacetonate ion, diamine = N,N′-dimethyl,N′-benzyl-1,2-diaminoethane and X = B(Ph)4−, PF6−, BF4− and ClO4−), have been prepared. The complexes were characterized on the basis of elemental analysis, molar conductance, UV–Vis and IR spectroscopies. Single crystals of [Cu(Cl-acac)(diamine)(H2O)]PF6, complex 2, were also characterized by X-ray diffraction. The influence of the solvent polarity and counter ions on the νmax values of the d–d bands of the complexes have been investigated by means of visible spectroscopy. All the complexes demonstrated negative solvatochromism. A multi-parametric equation has been utilized to explain the solvent effect on the d–d transition of the complexes using SPSS/PC software. The stepwise multiple linear regression (SMLR) method demonstrated that the donor power of the solvent plays the most important role in the solvatochromism of the compounds. The relative donor power of the anions X was determined by visible spectra in the solvent dichloromethane.

Four mixed-chelate complexes [Cu(Cl-acac)(diamine)]X were prepared. The complexes are solvatochromic. The solvatochromism of the complexes was studied using the SMLR method. The results suggest that the DN parameter of solvent makes a dominate contribution to the shift of the d–d band of the complexes.Figure optionsDownload as PowerPoint slideResearch highlights
► Mixed-chelate complexes of the type [Cu(Cl-acac)(diamine)]X (X = B(Ph)4−, PF6−, BF4− and ClO4−) were prepared.
► The complexes are soluble in organic solvents and show solvatochromism.
► The solvatochromism was tested using the SMLR computational method.
► The DN parameter of solvent makes a dominate contribution to the solvatochromism.