Synthesis, structural characterization and anticancer properties of nickel(II), copper(II) and zinc(II) 5,5 diethylbarbiturate complexes of pyridine based ligands

In this study, fourteen new nickel(II), copper(II) and zinc(II) complexes of 5,5-diethylbarbiturate (barb) with 1,10-phenantrolin (phen), 2,2'-dipyridylamine (dpya), bis(2-pyridylmethyl)amin (bpma) and 2,2':6',2''-terpyridine (terpy) were synthesized. The structures of the synthesized complexes were identified by elemental analysis, IR, UV-vis, ESI-MS and X-ray single crystal diffraction techniques. In addition, magnetic properties of the complexes were studied. Anticancer activity of the complexes was assessed by SRB assay in different cancer cells and compared to those of cis-platin. The barb and pyridine based ligands form a distorted octahedral geometry in [Ni(phen- κ2N,N')3]Cl(barb)∙7H2O, [Ni(barb-κ2N,O)(dpya-κ2N,N')2]Cl∙2H2O, [Cu(barb-κ2N,O)2(dpya-κ2N,N')]∙2H2O, [Ni(barb-κN)2(OH2)(bpma-κ3N,N',N'')]∙2Hbarb∙H2O, a distorted square pyramidal geometry in [Cu(barb-κN)(barb-κ2N,O)(phen-κ2N,N')]∙H2O, [Ni(barb-κN)2(terpy-κ3N,N',N'')]∙H2O, [Cu(barb-κN)2(terpy-κ3N,N',N'')]∙H2O, [Cu(barb)(OH2)(terpy-κ3N,N',N'')](barb)∙H2O, [Zn(barb-κN)2(terpy-κ3N,N',N'')]∙H2O complexes, a distorted trigonal bipyramidal geometry in Cu(barb-κN)2(bpma-κ3N,N',N'')]∙H2O, [Zn(barb-κN)2(bpma-κ3N,N',N'')]∙H2O, a tetrahedral geometry in [Zn(barb-κN)2(phen-κ2N,N')]∙H2O, [Zn(barb-κN)2(dpya-κ2N,N')] and a square planar geometry in [Cu(barb-κN)2(phen-κ2N,N')]. The UV−vis spectra of all the complexes in MeOH displayed a number of strong absorption bands in the UV region, due to ligand-centred transitions of the phen, dpya, bpma, terpy and barb moieties. Further, in the spectra of Ni(II) and Cu(II) complexes, relatively weak and broad absorption bands in the visible region are due to d–d transitions. The measured magnetic moments of the Ni(II) and Cu(II) complexes agree well with the calculated values for spin only d8 and d9 configurations. Key words: Nickel(II), Copper(II), Zinc(II), 5,5-diethylbarbiturate