Syntheses and structures of new trimetallic complexes bridged by N-(5-chloro-2-hydroxyphenyl)-N′-[3-(dimethylamino)propyl]oxamide: Cytotoxic activities, and reactivities towards DNA and protein

Two new μ-oxamido-bridged trinuclear complexes, namely [Cu3L2(H2O)2]{[Cu3L2]·2H2O}2 (1) and [Ni3L2(H2O)(DMF)](H2O)(DMF) (2), where L3− is deprotonated N-(5-chloro-2-hydroxyphenyl)-N′-[3-(dimethylamino)propyl]oxamide, have been synthesized and characterized by X-ray single-crystal diffraction. The structure of complex 1, which consists of three tricopper(II) neutral molecules, lies on an inversion centre at Cu5 atom and thus has a trans conformation. The structure of complex 2 composes of a trinickel(II) neutral molecule. In vitro cytotoxic activities, and the reactivities of the two complexes towards DNA and protein are investigated. Cytotoxicities experiments reveal that the two trinuclear complexes both exhibits cytotoxic effects against human hepatocellular carcinoma cell SMMC-7721 and human lung adenocarcinoma cell A549. The interactions of the two complexes with herring sperm DNA (HS-DNA) are investigated by using UV absorption and fluorescence spectra and viscometry. The results suggested that both of the two trinuclear complexes could interact with HS-DNA through the intercalation mode and follow the binding affinity order of 1 > 2. The reactivity towards protein BSA revealed that the quenching of BSA fluorescence by the two complexes are static quenching, and complex 1 exhibits a higher BSA-binding ability than that of complex 2.