Synthesis and characterization of a new family of binuclear copper(II) complexes with a flexible bridge and the π–π type charge-transfer interaction with 1,3,5-trinitrobenzene

Abstract

copper(II) complexes with unsymmetrical quadridentate Schiff bases, composed of the 1 : 1 : 1 condensation products of salicyladehyde derivatives (salicylaldehyde, 2-hydroxy-1-1-naphthalenecarbaldehyde, o-hydroxyacetophenone), diamine (ethylenediamine, trimethylenediamine), and acetylacetone, react electrophilically with hexamethylene di-isocyanate or m-xylene di-isocyanate in 2 : 1 mol ratio to produce the binuclear copper(II) complexes with a hexamethylene dicarbamoyl or m-xylene dicarbamoyl bridging group. The binuclear copper(II) complexes were characterized by elemental analyses, melting points, molecular weights, and i.r., e.s.r., and electronic spectra. The binuclear copper(II) complex containing a naphthalene moiety as π-electron donor interacts with 1,3,5-trinitrobenzene (tnb) to form a 1 : 1 molecular complex exhibiting a new absorption band attributable to the charge transfer between the naphthalene moiety and tnb, both in the solid and in solution. The 1 : 1 molecular complex between the mononuclear parent complex and tnb showed the charge-transfer band in the solid but not in solution.