Vibrational study of cytotoxic bis(1-ethylimidazole)L(-)malatoplatinum(II)

In this work, we present the FT-Raman and FT-IR spectra (4000-100 cm(-1)) of the newly synthesized cytotoxic platinum complex, bis(1-ethylimidazole)L(-)malatoplatinum(II), (abbr.: I) and reference substances: L(-)malic acid, silver L(-)malate and 1-ethylimidazole. Assignment of the bands was done on the basis of characteristic group vibrations, in comparison with the spectra of I with reference compounds as well as using the Literature and our previous data. Using water solution and deuterated samples of I and of L-malic acid was helpful in making an assignment. The spectral analysis confirmed the chelated structure of I and indicated that in contrast to references containing L(-)malate ion, the L(-)malatoplatinum complex I does not form intramolecular hydrogen-bonded cyclic structures in solid state. The intermolecular hydrogen bonding is, however, possible. The characteristic vibrations at the Pt2+ centre was observed below 600 cm(-1), the nu(Pt-N) and nu(Pt-O) in the range 600-430 cm(-1), whereas the delta skeletal, delta(N-Pt-N), delta(N-Pt-O) and delta(O-Pt-O), appeared in the lowest part of the observed spectra. In the spectra of reference compounds, the most important are assignments of the band at 323 cm(-1) of silver malate as nu(Ag-O), as well as the bands at 743 cm(-1) of L-malic acid and at 801 cm(-1) of silver malate, as intramolecular hydrogen bonded cyclic structures. Both bands are the most intense in their Raman spectra and might be used as analytical bands. (C) 2000 Elsevier Science B.V. All rights reserved.