Syntheses of dinuclear copper(II) complexes containing of tertiary diamine and amido groups with hydroxo bridges; chromotropic properties

Two new symmetric dinuclear complexes type [Cu(L)(m-OH)]2(ClO4)2, where either L ¼ N,N-dimethyl,N0-3-propylamide-ethylenediamine or N,N-diethyl,N0-3-propylamide-ethylenediamine were synthesized and characterized on the basis of elemental analysis, conductance measurement, spectroscopic techniques and X-ray crystal analysis. The complexes show halochromism in aqueous solution. The pH effects on the visible absorption spectra of the two complexes were studied which act as pH-induced “offeoneoff” switches through protonation and deprotonation in aqueous solution at room temperature. The dinuclear complexes were also observed to exhibit thermochromism, solvatochromism and ionochromism as a result of hemilability of amide groups. The solvatochromism of the complexes was investigated with different solvent parameter models using stepwise multiple linear regression method. The results suggested that the donor number parameter of the solvent has a dominant contribution to the shift of the ded absorption band of the complexes.