The coordinating ability of the antibiotic cycloserine towards transition metal halides

Abstract

A series of cycloserine complexes of chromium(III), manganese(II), rhodium(III) and iridium(III) halides has been prepared and characterized by chemical analyses, conductivity measurements, room temperature magnetic moment studies, electronic, i.r. and far-i.r. spectra and isotope exchange (deuteration) experiments. From the magnetic properties it was concluded that the above ligand forms high- spin complexes with chromium(III) and manganese(II) and low-spin complexes with rhodium(III) and iridium(III). The position and multiplicity of the metal-halogen stretching modes in the far-i.r. region have been extensively investigated, the results being particularly useful in distinguishing between the mer and fac isomers in the ML3X3-type octahedral complexes. The ligand behaves as monodentate O-bonded. The wavelengths of the principal electronic absorption peaks have been accounted for quantitatively in terms of the crystal field theory and the various parameters have been calculated. The calculated Dq parameters are in accord with the presence of CrO6, CrN3X3, RhO3X3 and IrO3X3 chromophores according to the infrared results. The values of B and C obtained for the manganese complexes are significantly lower than the corresponding values for the free gaseous ion. Under our experimental conditions no metal-induced ring opening of the ligand was observed.