Synthesis, Structural and Biological Studies of Some Half-Sandwich d6-Metal Complexes with Pyrimidine-Based Ligands

The reaction of metal precursors {[Cp*MCl2]2 (M=Rh, Ir)} with 2-aminopyrimidine (L1) gave binuclear complexes as [(Cp*MCl2)2(μ-L1)], where L1 acted as a bridging ligand. While 2-mercaptopyrimidine (L2) with [Cp*MCl2]2 {M=Rh(III), Ir(III)} formed mononuclear di substituted complexes as [Cp*M(L2)2], where L2 acted as a chelating as well as a monodentate ligand. The reaction of [CpRu(PPh3)2Cl] with 2-mercaptopyrimidine (L2) led to the formation of mononuclear complex as general formula [CpRu(PPh3)(L2)] in presence of a base. 2-Mercaptopyrimidine ligand resulted complexes with strained four-membered metallacycle while 2-aminopyrimidine yielded bridged complexes. HOMO-LUMO energy gaps and UV-Visible bands were additionally rationalised by the DFT studies. The binding ability of the complexes to the CT-DNA was confirmed using UV-Visible and fluorescence spectroscopy. In vitro antibacterial activity of the complexes was evaluated against human pathogenic bacteria. Cytotoxicity of the complexes was examined by the MTT assay over three cancerous and one non-cancer cell lines viz., BE, HT-29, MIA−Pa-Ca2 and ARPE-19.