Preparation, physicochemical properties and biological activity of copper(II) complexes with 6-(2-chlorobenzylamino)purine (HL1) or 6-(3-chlorobenzylamino)purine (HL2). The single-crystal X-ray structure of [Cu(H+L2)(2)Cl-3]Cl-2H(2)O

Copper(II) complexes of 6-(2-chlorobenzylamino)purine (HL,) and 6-(3-chloro benzylamino)purine (HL2), respectively, were prepared. Depending on the pH of the medium and the molar ratio of reactants the following mononuclear (t rigonal-bipyramidal) and dinuclear (octahedral, trigonal-bipyramidal or tet rahedral) complexes were isolated: [Cu-2(mu -HL1)(2)(mu -Cl-2)(2)(HL1)(2)Cl -2] (1a,b), [Cu-2(mu -Cl)(2)(mu -L-1)(2)(H2O)(2)] (2a), [Cu-2(mu -Cl)(2)(mu -L-2)(2)(H2O)(2)] (2b), [Cu(H+L2)(2)Cl-3]Cl .H2O (3a,b), [Cu-2(mu -Cl)(2)( HL1)(2)Cl-2] (4a), and [Cu-2(mu -Cl)(2)(HL2)(2)Cl-2] (4b). The compounds we re characterized by elemental analyses, electronic, infrared and mass (FAB, ES+) spectral data, magnetic susceptibility temperature dependence measur ements and molar conductivity data. An X-ray single-crystal structural anal ysis of [Cu(H+L2)(2)Cl-3]Cl . 2H(2)O (3b) showed that the Cu2+ ion is penta -coordinated by three chloride ions and by two H+L2 ligands. Thus, the Cu2 ion adopts a distorted trigonal bipyramidal coordination geometry with the protonated H+L2 ligands coordinated in trans apical positions, while the t hree chloride ions are situated in an equatorial plane. The cytotoxic activ ity of the complexes was determined by a calcein AM assay. Mouse melanoma c ell line B16-FO, human malignant melanoma cell line G361, human osteogenic sarcoma cell line HOS and human breast adenocarcinoma cell line MCF7 were u sed. IC50 values, the drug concentrations lethal to 50% of the tumor cells, were estimated. One of the important mechanisms responsible for the cytoto xicity of cytokinin-derived compounds, the inhibition of cyclin-dependent k inases by the studied complexes, was also determined. (C) 2001 Elsevier Sci ence B.V. All rights reserved.