Syntheses and characterization of copper(II) complexes with Schiff-base ligands derived from ethylenediamine, diphenylethylenediamine and nitro, bromo and methoxy salicylaldehyde

Copper(II) quelates with Schiff bases derived from ethylenediamine, 1R,2R-( +)- or 1S,2S-(-)-1,2-diphenylethylenediamine and 5-X-salicylaldehyde (X=OCH 3, H, Br, NO2) have been synthesized and characterized by elemental analysi s and IR and UV-visible spectroscopies. The ORD and CD spectra of the chira l ligands and their related complexes have also been measured. The absorpti on and CD spectra of the metal complexes in the visible region are consiste nt with near. square planar coordination geometries. Trends in absorption s pectra over the series of complexes can be correlated with electronic effec ts of the substituents at position 5 of the salicylaldehyde. The sign patte rns of the CD spectra in both UV and visible regions suggest the prevalence of S and A conformations for the chelate ring in the complexes of Schiff b ases derived, respectively, from R,R- and S,S-diamines. Specific features o f the CD spectra of the metal complexes are discussed in terms of the excit on chirality method. (C) 1999 Elsevier Science Ltd. All rights reserved.