Dinuclear Copper(II) Complex of Containing N,N-diisopropyl,N'-3-propylamide-ethylenediamine, and Dihydroxo Bridge; Solvatochromic and Thermochromic

The synthesis and characterization of a dinuclear [LCu(m-OH)2CuL](ClO4)2, complex with a tridentate N,N-diisopropyl,N'-3-propylamide-ethylenediamine hemilabile ligand (abbreviated L) is reported. The dinuclear complex was characterized by elemental analysis, molar conductance, thermal analysis, and spectral studies. In the complex, both copper centers are 5-coordinated and bridged through two hydroxo groups.  Thermo- and solvatochromic behaviors of the complex were investigated by visible spectroscopy. Its reversible thermochromism (blue ↔ green) in acetonitrile solution is due to dissociation and re-coordination of Cu-O(amide) moiety. The solvent-dependent absorption maxima, lmax, was studied by a Stepwise Multiple Linear Regression (SMLR) analysis to determine the best model describing the resulting positive solvatochromism.  The statistical results demonstrated that among different solvent parameters, Donor Number (DN) is a dominant parameter that is responsible for the redshift in the d-d absorption band of the complex by increasing its values.