Synthesis and structure of a new tetracopper(II) complex bridged both by oxamido and phenolato groups: Cytotoxic activity, and reactivity towards DNA and BSA

A new tetracopper(II) complex bridged both by oxamido and phenolato groups, namely [Cu4(chmpoxd)2(dabt)2](ClO4)2, where H3chmpoxd and dabt stand for N-(5-chloro-2-hydroxyl-phenyl)-N′-[3-(methylamino)propyl]oxamide and 2,2′-diamino-4,4′-bithiazole, respectively, has been synthesized and characterized by elemental analyses, molar conductance measurements, IR and electronic spectra studies, and single-crystal X-ray diffraction. The crystal structure reveals a centrosymmetric circular tetranuclear cation [Cu4(chmpoxd)2(dabt)2]2+ assembled by a pair of cis-oxamido-bridged bicopper(II) units via μ2-phenolato bridges, in which one copper(II) atom is located in a slightly distorted square-planar environment, while the other is in a square-pyramidal geometry. The Cu⋯Cu separations through the oxamido and the phenolato bridges are 5.2217(12) and 3.7042(11) Å, respectively. In vitro cytotoxicity experiment shows that the tetracopper(II) complex exhibits cytotoxic activity against the SMMC7721 and A549 cell lines. The reactivities towards HS-DNA and protein BSA revealed that the tetracopper(II) complex can interact with HS-DNA in the mode of intercalation, and the complex binds to BSA responsible for quenching of tryptophan fluorescence by static quenching mechanism.

► The first tetracopper(II) complex bridged both by μ-oxamido and μ2-phenolate groups in asymmetrical N,N′-bis(substituted)oxamides was synthesized and structurally characterized by X-ray single-crystal diffraction.
► The complex exhibits potent in vitro antitumor activities against SMMC-7721 and A549 cell lines.
► The complex interacts with HS-DNA by intercalation and binds to protein BSA for quenching of tryptophan fluorescence by static quenching mechanism.
► The present results have attested that the affinity magnitudes toward HS-DNA and BSA, and cytotoxic activities may be controlled and tuned by playing the nature of the bridging ligands in tetranuclear complexes.