Synthesis, structural characterization, antimicrobial and cytotoxic effects of aziridine, 2-aminoethylaziridine and azirine complexes of copper(II) and palladium(II)

The synthesis, spectroscopic and X-ray structural characterization of copper(II) and palladium(II) complexes with aziridine ligands as 2-dimethylaziridine HNCH2CMe2 (a), the bidentate N-(2-aminoethyl)aziridines C2H4NC2H4NH2 (b) or CH2CMe2NCH2CMe2NH2 (c) as well as the unsaturated azirine NCH2CPh (d) are reported. Cleavage of the cyclometallated Pd(II) dimer [mu-Cl(C6H4CHMeNMe2-C,N)Pd](2) with ligand a yielded compound [Cl(NHCH2CMe2)(C6H4CHMe2NMe2-C, N)Pd] (1a). The reaction of the aziridine complex trans-[Cl2Pd(HNC2H4)(2)] with an excess of aziridine in the presence of AgOTf gave the ionic chelate complex trans-[(C2H4NC2H4NH2-N,N')(2)Pd](OTf)(2) (2b) which contains the new ligand b formed by an unexpected insertion and ring opening reaction of two aziridines ("aziridine dimerization"). CuCl2 reacted in pure HNC2H4 or HNCH2CMe2 (b) again by "dimerization" to give the tris-chelated ionic complex [Cu(C2H4NC2H4NH2-N,N')(3)]Cl-2 (3b) or the bis-chelated complex [CuCl (C2H2Me2NC2H2Me2NH2-N,N')(2)]Cl (4c). By addition of 2H-3-phenylazirine (d) to PdCl2, trans-[Cl2Pd (NCH2CPh)(2)] (5d) was formed. All new compounds were characterized by NMR, IR and mass spectra and also by X-ray structure analyses (except 3b). Additionally the cytotoxic effects of these complexes were examined on HL-60 and NALM-6 human leukemia cells and melanoma WM-115 cells. The antimicrobial activity was also determined. The growth of Gram-positive bacterial strains (S. aureus, S. epidermidis, E. faecalis) was inhibited by almost all tested complexes at the concentrations of 37.5-300.0 mu g mL(-1). However, MIC values of complexes obtained for Gram-negative E. coli and P. aeruginosa, as well as for C. albicans yeast, mostly exceeded 300 mu g mL(-1). The highest antibacterial activity was achieved by complexes 1a and 2b. Complex 2b also inhibited the growth of Gram-negative bacteria.