Infrared Spectra of Bis(L-serinato)nickel(H) Dihydrate by Using Metal Isotope Technique

The infrared spectra of bis(L-serinato)nickel(II) dihydrate (Ni(L-ser)₂ • 2H₂0) and their isotopic complexes containing ⁵⁸Ni, ⁶²Ni and deuterium have been measured in the region between 4000 and 200 cm¹. The shifts caused by nickel and hydrogen isotopic substitutions indicate that three bands at 342,297 and 222 cm “¹ are Ni-ligand stretching vibrations complicatedly coupled with Ni-O and Ni-N stretching vibrations. The conformational differences between gauche-anti and anti-gauche serinates in metallo-serinate complexes are characterized by the COO deformation vibrations. A normal coordinate analysis on the basis of a complete molecular conformation of Ni(L-ser)₂ • 2H₂0 and an intermolecular force field reproduced well the observed frequencies and isotope shifts. In addition, the calculated result is consistent with both the empirical assignments and the observed frequency differences caused from the conformational differences.