Isotopic studies of the metal-ligand vibrations in histamine complexes with copper(II).

Two known copper complexes of the formulae Cu(hm)2(ClO4)2, Cu(hm)Cl2 and new, Cu(hm)Br2 (hm = histamine) have been investigated in the 600-50 cm(-1) far-infrared region. Assignments of vibrations related to metal-ligand bonds have been made based on metal isotope substitution, partial deuteration and halogen sensitivity. Copper-hm stretching vibrations have been localised at 420, 417 and 411 cm(-1) for modes involving amine nitrogen and at 282, 270, 259 cm(-1) for those of imidazole nitrogen. Vibrational coupling between some metal-ligand modes has been postulated.