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Abstract
A new tetracopper(II) complex bridged by oxamido and carboxylate, [Cu4(bhyox)2(phen)2(H2O)2](pic)2, where H3bhyox, phen and Hpic denote N-benzoate-N′-[2-(2-hydroxyethylamino)ethyl]oxamide, 1,10-phenanthroline, and 2,4,6-trinitrophenol, respectively, has been synthesized and characterized by elemental analysis, molar conductivity, IR, electronic spectra, and single-crystal X-ray diffraction. The crystal structure reveals that the cyclic tetracopper(II) cation [Cu4(bhyox)2(phen)2(H2O)2]2+ with an embedded center of inversion is assembled by a pair of cis-oxamido-bridged bicopper(II) units via carboxylate bridges, in which copper(II) ions are distorted square pyramidal. The Cu⋯Cu separations through the oxamido and the carboxylate bridges are 5.1944(6) and 5.3344(7) Å, respectively. In the crystal, the supramolecular structure is composed of classical hydrogen bonding chains assembled by 2D non-classical hydrogen-bonding networks and π–π stacking interaction. In vitro cytotoxicity experiment shows that the tetracopper(II) complex exhibits cytotoxic activity against the SMMC7721 and A549 cell lines. The reactivity towards herring sperm DNA (HS-DNA) and protein bovine serum albumin (BSA) suggests that the tetracopper(II) complex can interact with the DNA by intercalation, and the complex binds to protein BSA responsible for quenching of tryptophan fluorescence by static quenching mechanism.
Acknowledgments
This project was supported by the National Natural Science Foundation of China (Nos. 21071133, 51273184 and 81202399), the Program for Science and Technology of Shandong Province (No. 2011GHY11521), and the Natural Science Foundation of Qingdao City [Nos. 11-2-4-1-(9)gch), 12-1-3-52-(1)-nsh and 12-1-4-16-(7)-jch].