Structural, photolysis and biological studies of the bis(μ2-chloro)-tris(triphenylphosphine)-di-copper(I) and chloro-tris(triphenylphosphine)-copper(I) complexes. Study of copper(I)–copper(I) interactions

Direct reaction of copper(I) chloride with triphenylphosphine (tpp) in molar ratio 2:3 and 1:3, results in the formation of the [(tpp)Cu(μ2-Cl)2Cu(tpp)2] (1) and {[CuCl(tpp)3]·(CH3CN)} (2) complexes. The complexes have been characterized by melting point, FT-IR, UV–Vis spectroscopic data and X-ray crystallography. Complex 1 is di-nuclear. Two μ2-Cl atoms bridge two copper(I) ions with tetrahedral and trigonal geometry respectively. The short copper–copper bond distance of 2.9039(6) Ǻ in case of 1 indicates d10–d10 interaction between metal centers. Thus, our studies were extended here in the determination of the quasi-aromaticity, which results in strong Cu–Cu interactions, using the computational method of nucleus-independent chemical shifts (NICS). The NICS calculated at the inner region of the Cu2Cl2P3 core in complex 1 is shielded up to −6.05 ppm. Complex 2 is mono-nuclear where three phosphorus and one chloride atoms form a tetrahedron around the copper(I) ion. Photolysis of both complexes 1 and 2, results in the formation of triphenylphosphine oxide. mplexes 1 and 2, were tested for their in vitro cytotoxic activity against leiomyosarcoma cells (LMS) and human breast adenocarcinoma cells (MCF-7). The type of LMS cell death caused by the complexes was also evaluated by use of a flow cytometry assay. The results show that at concentration of 5 μΜ of complexes 1 and 2, 34.1% (1) and 19.6 (2)% of LMS cells undergo programmed cell death (apoptosis), while at 10 μΜ, 80.4% (1) and 65.2% (2) of LMS cells undergo apoptosis. The light sensitivity of the complex is discussed in relation with the biological activity.