Carbonyl-heterobimetallic Ru(II)/Fe(II)-complexes containing polypyridyl ligands: Synthesis, characterization, cellular viability assays and interactions with biomolecules.

This paper describes on the interaction studies of carbonyl heterobimetallic compounds of Ru(II)/Fe(II) containing polypyridyl ligands, with general formula ct-[RuCl(CO)(N-N)(dppf)]PF6, N-N = 1,10-phenanthroline (phen) 5; dipyrido[3,2-f:2',3'-h]quinoxaline (dpq) 6; dipyrido[3,2-a:2',3'-c]phenazine (dppz) 7; dipyrido[3,2-f:2',3'-h]quinoxalino[2,3-b]quinoxaline (dpqQX) 8 and dppf = 1,1'-bis(diphenylphosphino) ferrocene], with calf thymus DNA (ct-DNA) and bovine serum albumin (BSA). Also, it describes the cellular viability assays of these complexes in tumorigenic and non-tumorigenic cell lines. The carbonyl complexes 5-8 and their respective precursors with formula cis-[RuCl2(N-N)(dppf)], N-N = phen (1), dpq (2), dppz (3) and dpqQX (4), were characterized by elemental analysis and spectroscopic techniques (FTIR, UV-vis, 1H and 31P{1H} NMR). Also, a cyclic voltammetry study was performed for all complexes. The crystal structure of the complex 3 is presented and discussed. Spectrofluorimetric titrations shows spontaneous and strong interaction of 5-8 with BSA, through a static quenching mechanism, resulting in binding constants in the order of 104-106 L mol-1, at 310 K. Viscosity measurements and circular dichroism spectra prompts interactions of 5-8 with ct-DNA via non-classical intercalations or by an electrostatic pathway. MTT assays in breast tumor cells MDA-MB-231 and in non-tumorigenic cells MCF-10A and V79-4 cell lines revealed IC50 values ranging from 0.19 to 1.11 µmol L-1, 1.07-3.18 µmol L-1 and 1.29-3.85 µmol L-1 respectively, for complexes 5-8.

The trans-[Ru(PPh3)2(N,N-dimethyl-N'-thiophenylthioureato-k2O,S)(bipy)]PF6 complex has pro-apoptotic effects on triple negative breast cancer cells and presents low toxicity in vivo.

Triple negative breast cancer (TNBC) is a heterogeneous subtype of breast tumors that does not exhibit the expression of estrogen and progesterone receptors, neither the amplification of the human epidermal growth factor receptor 2 (HER-2) gene. Despite all the advances in cancer treatments, the development of new anticancer drugs for TNBC tumors is still a challenge. There is an increasing interest in new agents to be used in cancer treatment. Ruthenium is a metal that has unique characteristics and important in vivo and in vitro results achieved for cancer treatment. Thus, in this work, with the aim to develop anticancer drugs, three new ruthenium complexes containing acylthiourea ligands have been synthesized and characterized: trans-[Ru(PPh3)2(N,N-dibutyl-N'-benzoylthioureato-k2O,S)(2,2'-bipyridine (bipy))]PF6(1), trans-[Ru(PPh3)2(N,N-dimethyl-N'-thiophenylthioureato-k2O,S)(bipy)]PF6(2) and trans-[Ru(PPh3)2(N,N-dimethyl-N'-benzoylthioureato-k2O,S)(bipy)]PF6(3). Then, the cytotoxicity of these three new ruthenium complexes was investigated in TNBC MDA-MB-231 and in non-tumor MCF-10A cells. Complex (2) was the most selective complex and was chosen for further studies to verify its effects on cell morphology, adhesion, migration, invasion, induction of apoptosis and DNA damage in vitro, as well as its toxicity and capacity of causing DNA damage in vivo. Complex (2) inhibited proliferation, migration, invasion, adhesion, changed morphology and induced apoptosis, DNA damage and nuclear fragmentation of TNBC cells at lower concentrations compared to non-tumor MCF-10A cells, suggesting an effective action for this complex on tumor cells. Finally, complex (2) did not induce toxicity or caused DNA damage in vivo when low doses were administered to mice.

Nitrosyl induces phosphorous-acid dissociation in ruthenium(II).

The trans-[Ru(NO)(NH(3))(4)(P(OH)(3))]Cl(3) complex was synthesized by reacting [Ru(H(2)O)(NH(3))(5)](2+) with H(3)PO(3) and characterized by spectroscopic ((31)P-NMR, δ = 68 ppm) and spectrophotometric techniques (λ = 525 nm, ε = 20 L mol(-1) cm(-1); λ = 319 nm, ε = 773 L mol(-1) cm(-1); λ = 241 nm, ε = 1385 L mol(-1) cm(-1); ν(NO(+)) = 1879 cm(-1)). A pK(a) of 0.74 was determined from infrared measurements as a function of pH for the reaction: trans-[Ru(NO)(NH(3))(4)(P(OH)(3))](3+) + H(2)O ⇌ trans-[Ru(NO)(NH(3))(4)(P(O(-))(OH)(2))](2+) + H(3)O(+). According to (31)P-NMR, IR, UV-vis, cyclic voltammetry and ab initio calculation data, upon deprotonation, trans-[Ru(NO)(NH(3))(4)(P(OH)(3))](3+) yields the O-bonded linkage isomer trans- [Ru(NO)(NH(3))(4)(OP(OH)(2))](2+), then the trans-[Ru(NO)(NH(3))(4)(OP(H)(OH)(2))](3+) decays to give the final products H(3)PO(3) and trans-[Ru(NO)(NH(3))(4)(H(2)O)](3+). The dissociation of phosphorous acid from the [Ru(NO)(NH(3))(4)](3+) moiety is pH dependent (k(obs) = 2.1 × 10(-4) s(-1) at pH 3.0, 25 °C).

Reactivity of radicals generated on irradiation of trans-[Ru(NH3)4(NO2)P(OEt)3](PF6).

The electronic absorption spectrum of trans-[Ru(NH(3))(4)(NO(2))(P(OEt)(3)](+) in aqueous solution is characterized by a strong absorption band at 334 nm (lambda(max) = 1800 mol(-1) L cm(-1)). On the basis of quantum mechanics calculations, this band has been assigned to a MLCT transition from the metal to the nitro ligand. Molecular orbital calculations also predict an LF transition at 406 nm, which is obscured by the intense MLCT transition. When trans-[Ru(NH(3))(4)(NO(2))(P(OEt)(3)](+) in acetonitrile is irradiated with a 355 nm pulsed laser light, the absorption features are gradually shifted to represent those of the solventocomplex trans-[Ru(NH(3))(4)(solv)(P(OEt)(3)](2+) (lambda(max) = 316 nm, epsilon = 650 mol(-1) L cm(-1)), which was also detected by (31)P NMR spectroscopy. The net photoreaction under these conditions is a photoaquation of trans-[Ru(NH(3))(4)(NO(2))(P(OEt)(3)](+), although, after photolysis, the presence of the nitric oxide was detected by differential pulse polarography. In phosphate buffer pH 9.0, after 15 min of photolysis, a thermal reaction resulted in the formation of a hydroxyl radical and a small amount of a paramagnetic species as detected by EPR spectroscopy. In the presence of trans-[Ru(NH(3))(4)(solv)P(OEt)(3)](2+), the hydroxyl radical initiated a chain reaction. On the basis of spectroscopic and electrochemical data, the role of the radicals produced is analyzed and a reaction sequence consistent with the experimental results is proposed. The 355 nm laser photolysis of trans-[Ru(NH(3))(4)(NO(2))(P(OEt)(3)](+) in phosphate buffer pH 7.4 also gives nitric oxide, which is readily trapped by ferrihemeproteins (myoglobin, hemoglobin, and cytochrome C), giving rise to the formation of their nitrosylhemeproteins(II), (NO)Fe(II)hem.