Synthesis, structural, thermal elucidation and in vitro anticancer activity of novel silver(I) complexes with non-steroidal anti-inflammatory drugs diclofenac and mefenamic acid including picoline derivatives

Six new Ag(I) coordination complexes, namely [Ag4(μ-dicl)4(2-pic)3] 1, [Ag2(μ-mef)2(2-pic)2] 2, [Ag2(μ-dicl)2(3-pic)2] 3, [Ag2(μ-mef)2(3-pic)2] 4, [Ag2(μ-dicl)2(4-pic)2] 5 and [Ag2(μ-mef)2(4-pic)2] 6, were synthesized and characterized by elemental analysis, FT-IR and thermal analysis techniques. The crystal structures of 1, 3, 4 and 5 were determined by X-ray diffraction analysis, whereas 2 and 6 were obtained as microcrystalline powders. X-ray diffraction analysis demonstrated that 1 occurs as a tetranuclear complex, while 3, 4 and 5 have binuclear structures. A short Ag⋯Ag distances of 2.8446 and 2.8823 A for 1, 2.8409 A for 3, 2.8942 A for 4 and 2.8423 A for 5 were found in the complexes, indicating that argentophilic interactions exist between the silver ions. In 1, the dicl ligands act as μ3-O,O′,O′ bridging ligands between three Ag(I) ions. In 3, 4 and 5, the dicl and mef ligands behave as bridging ligands and bind two Ag(I) ions together with the carboxylato oxygen atoms. The simultaneous TG/DTG and DTA techniques were applied to interpret the mass losses, decomposition temperatures and corresponding processes of the thermal behaviours of the complexes. The experimental and calculated mass losses of the proposed structures for complexes 2 and 6 are quite compatible with each other and these complexes have very similar FT-IR spectra to the other complexes, which reflect their same structural geometries and characteristics. The cytotoxic activities of the complexes (1–6) were tested against three different cancer cell lines, MCF-7, HT-29 and HepG2, and one normal cell line, 3 T3-L1. XTT assay results demonstrated that although all the silver(I) complexes showed good cytotoxic activity, depending on the cell types tested, the complexes with mefanamic acid (2, 4 and 6) were found to predominate over those with diclofenac (1, 3 and 5), as well as the superiority of 3-picoline to 4-picoline and 2-picoline. Moreover, compared with the cytotoxic potential of carboplatin, 4 especially exhibited a significant cancer cell inhibitory rate and lower cytotoxicity toward the normal cell line, with much higher selectivity indexes.