Synthesis, Physicochemical and Theoretical Studies on New Rhodium and Ruthenium Dimers. Relationship Between Structure and Cytotoxic Activity

Two dimeric compounds of the general formulae (Et3NH)(2)[Rh-2(mu(2)-L)(4)Cl-2] (1) (where L = thiophene-2-carboxylate) and [((eta(6)-p-cymene)Ru)(2)(mu-Cl)(3)]PF6 (2) have been synthesized using a new method. The unique anionic complex 1 (space group P bca) has octahedral coordination in which the equatorial positions are occupied by the oxygen atoms of four thiophene-2-carboxylates in a paddle wheel fashion. In complex 2 (space group P1), each Ru(II) ion exhibits a pseudo-octahedral, three-legged piano-stool geometry. The electronic structure and absorption spectral features of 1 were also investigated by means of absorption spectroscopy (UV-Vis) and TD-DFT calculations. The biological studies of 1 and 2, such as cytotoxicity, lipophilicity and interactions with DNA and BSA, point on structure-cytotoxic activity relationship of obtained dimers. The results obtained via MTT, SRB assays, UV-Vis and CD spectroscopy, suggest that the rhodium dimer interacts with DNA via groove binding, whereas 2 binds to DNA via electrostatic interactions only. The effect of the dimeric complexes on the cytotoxicity of three human cancer lines, myelomonocytic leukaemia (MV-4-11), colon adenocarcinoma (LoVo) and breast adenocarcinoma (MCF-7), as well as on normal mice fibroblast cells (BALB/3T3), has been screened. Cisplatin was used as a reference drug. As a general observation, the properties reported in this paper suggest that the rhodium complex has considerable potential as an anticancer agent against myelomonocytic leukaemia (IC50 = 4.02 mu M). (C) 2018 Elsevier Ltd. All rights reserved.