Vibrational studies of the solid imidazole and pyridine adducts of metal(II) saccharinates I. The OH/OD and NH/ND stretching regions of the cobalt(II) and nickel(II) complexes

FT-IR spectra of both protiated and deuterated analogues of the complexes [M(HIm)₄(H₂O)₂](sac)₂ and [M(H₂O)₄(py)₂](sac)2·4H₂O (M = Co, Ni) in the region of the water stretching modes, at room temperature down to the liquid-nitrogen boiling temperature, are recorded and discussed. The regions of the NH/ND stretchings in the spectra of the imidazole saccharinate+s are also studied. The appearance of the bands that are mainly due to the OH, OD, NH and ND stretchings is discussed in connection with the crystallographic data. The appearance of the NH stretching region in the spectra of the studied imidazole adducts is partly explained as a result of Evans-type Fermi resonance of the NH stretchings with non-fundamental modes. In spite of the existence of single type of asymmetrically bonded water molecules in the structures of the studied imidazole complexes, an unexpected ratio 1:2 of the integral intensities of the two isotopically isolated v(OD) stretchings in their spectra was found. (C) 2000 Editions scientifiques et medicales Elsevier SAS.