MOLECULAR-STRUCTURES AND INFRARED-SPECTRA OF 5-COORDINATE COPPER(II) COMPLEXES INCLUDING ONE TRIDENTATE DIETHYLENETRIAMINE LIGAND

The molecular structures of five-coordinate Cu(dien)L2 (dien=diethylenetriamine; L=NO3-, Br-, Cl-, ClO4-) have been examined by molecular mechanics (MM2). All compounds have dien in the meridional (mer) position and k,k' (symmetric) conformation. The dien position, however, differs from the rigorous mer form as to the NCuN (N-terminal) being less than the expected 180-degrees. The IR bands of these compounds in the 50-4000 cm-1 range have been recorded in the solid state and assigned on the basis of normal coordinate analysis (potential energy distribution) of the dien molecule. The experimental IR spectra of the studied compounds were compared with frequencies calculated by the MOPAC 6.0 package assuming dien to be coordinated in fac and mer positions. The comparison shows that in fact the dien ligand in the studied compounds should be midway between the fac and mer positions.