Syntheses and identification of cefotaxime-non-transition metal complexes

The coordination chemistry of the biologically active cefotaxime sodium and, in particular, the mode of its interaction with some metal ions of electronic configuration d0 (alkaline earth) and others, Zn(II), Pb(II), and Ce ions with the electronic configuration d10  has been investigated. Seven complexes were synthesized, isolated in the solid-state, and characterized by elemental analyses, conductivity measurements, IR and UV/VIS spectra, as well as thermal analyses. Based on the obtained experimental data and literature, the structural formulae to these complexes were suggested and formulated as [Mg(cef)2].2H2O (1), [Ca(cef)2].2H2O (2) [Sr(cef)2].2H2O (3), [Ba(cef)2].2H2O (4), [Zn(cef)2(H2O)2] (5), [Pb(cef)2(H2O)2].4H2O (6) and [Ce(cef)2(H2O)2].3H2O (7). The data obtained show that cefotaxime interacted with metal in a molar ratio of 2:1, respectively. Cefotaxime bonded to metal ions in the anionic form as a bidentate ligand through the lactam carbonyl (C=O) and the carboxylate group (COO-). Tetrahedral and octahedral shapes were proposed as the most likely geometries associated with a metal having such electronic configurations. The absorption bands observed in the electronic spectrum of free cefotaxime are also observed with some shifts in the spectra of its complexes, indicating their formation. The absorption bands of free cefotaxime and its complexes were assigned to electronic transitions. The thermal analyses date strongly support the structures proposed for the complexes and indicate the formation of the corresponding metal oxide as a final decomposition product.