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Four new Cu/PPh3/naphtoquinone complexes were synthesized, characterized (IR, UV/visible, 1D/2D NMR, mass spectrometry, elemental analysis, and X-ray diffraction), and evaluated as anticancer agents. We also investigated the reactive oxygen species (ROS) generation capacity of complex 4, considering the well-established photochemical property of naphthoquinones. Therefore, employing the electron paramagnetic resonance (EPR) "spin trap", 5,5-dimethyl-1-pyrroline N-oxide (DMPO) technique, we identified the formation of the characteristic •OOH species (hydroperoxyl radical) adduct even before irradiating the solution containing complex 4. As the irradiation progressed, this radical species gradually diminished, primarily giving rise to a novel species known as •DMPO-OH (DMPO + •OH radical). These findings strongly suggest that Cu(I)/PPh3/naphthoquinone complexes can generate ROS, even in the absence of irradiation, potentially intensifying their cytotoxic effect on tumor cells. Interpretation of the in vitro cytotoxicity data of the Cu(I) complexes considered their stability in cell culture medium. All of the complexes were cytotoxic to the lung (A549) and breast tumor cell lines (MDA-MB-231 and MCF-7). However, the higher toxicity for the lung (MRC5) and breast (MCF-10A) non-tumoral cells resulted in a low selectivity index. The morphological analysis of MDA-MB-231 cells treated with the complexes showed that they could cause decreased cell density, loss of cell morphology, and loss of cell adhesion, mainly with concentrations higher than the inhibitory concentration of 50% of cell viability (IC50) values. Similarly, the clonogenic survivance of these cells was affected only with concentrations higher than the IC50 values. An antimigratory effect was observed for complexes 1 and 4, showing around 20–40% of inhibition of wound closure in the wound healing experiments. [ABSTRACT FROM AUTHOR]

Copper nitrite reductase mimetics were synthesized using three new tridentate ligands sharing the same N,N,N motif of coordination. The ligands were based on L -proline modifications, attaching a pyridine and a triazole to the pyrrolidine ring, and differ by a pendant group (R = phenyl, n-butyl and n-propan-1-ol). All complexes coordinate nitrite, as evidenced by cyclic voltammetry, UV-Vis, FTIR and electron paramagnetic resonance (EPR) spectroscopies. The coordination mode of nitrite was assigned by FTIR and EPR as κ2O chelate mode. Upon acidification, EPR experiments indicated a shift from chelate to monodentate κO mode, and 15N NMR experiments of a Zn2+ analogue, suggested that the related Cu(II) nitrous acid complex may be reasonably stable in solution, but in equilibrium with free HONO under non catalytic conditions. Reduction of nitrite to NO was performed both chemically and electrocatalytically, observing the highest catalytic activities for the complex with n-propan-1-ol as pendant group. These results support the hypothesis that a hydrogen bond moiety in the secondary coordination sphere may aid the protonation step. [ABSTRACT FROM AUTHOR]

This manuscript describes the preparation of a new Ru(ii) nitrosylsulphito complex, trans-[Ru(NH3)4(isn)(N(O)SO3)]+ (complex 1), its spectroscopic and structural characterization, photochemistry, and thermal reactivity. Complex 1 was obtained by the reaction of sulfite ions (SO32−) with the nitrosyl complex trans-[Ru(NH3)4(isn)(NO)]3+ (complex 2) in aqueous solution resulting in the formation of the N-bonded nitrosylsulphito (N(O)SO3) ligand. To the best of our knowledge, only four nitrosylsulphito metal complexes have been described so far (J. Chem. Soc., Dalton Trans., 1983, 2465–2472), and there is no information about the photochemistry of such complexes. Complex 1 was characterized by spectroscopic means (UV-Vis, EPR, FT-IR, 1H- and 15N-NMR), elemental analysis and single-crystal X-ray diffraction. The X-ray structure of the precursor complex 2 is also discussed in the manuscript and is used as a reference for comparisons with the structure of 1. Complex 1 is water-soluble and kinetically stable at pH 7.4, with a first-order rate constant of 3.1 × 10−5 s−1 for isn labilization at 298 K (t1/2∼ 373 min). Under acidic conditions (1.0 M trifluoroacetic acid), 1 is stoichiometrically converted into the precursor complex 2. The reaction of hydroxide ions (OH−) with 1 and with 2 yields the Ru(ii) nitro complex trans-[Ru(NH3)4(isn)(NO2)]+ with second-order rate constants of 2.1 and 10.5 M−1 s−1 (at 288 K), respectively, showing the nucleophilic attack of OH− at the nitrosyl in 2 (Ru–NO) and at the nitrosylsulphito in 1 (Ru–N(O)SO3). The pKa value of the –SO3 moiety of the N(O)SO3 ligand in 1 was determined to be 5.08 ± 0.06 (at 298 K). The unprecedented photochemistry of a nitrosylsulphito complex is investigated in detail with 1. The proposed mechanism is based on experimental (UV-Vis, EPR, NMR and Transient Absorption Laser Flash Photolysis) and theoretical data (DFT) and involves photorelease of the N(O)SO3− ligand followed by formation of nitric oxide (NOṖ) and sulfite radicals (SO3Ṗ−, sulfur trioxide anion radical). [ABSTRACT FROM AUTHOR]

A novel mixed platinum(II) complex with general formula [Pt(PPh3)2(L1‐O,S)]PF6 has been synthetized and characterized by elemental analysis, molar conductivity, and by IR and NMR (1H, 13C and 31P) spectroscopic methods. The crystal structure has been determined by single‐crystal X‐ray crystallography. The molecule presents an almost ideal square‐planar geometry, and the crystal is stabilized by weak C–H···O and C–H···F hydrogen bonds, and C–H···π stacking interactions. The steric congestion of ligands is described by "exact" cone and solid cone angles, and the percentage of metal surface shielded by the ligands. The results are compared to closely related palladium complexes. The X‐ray structure revealed the proximity of the ortho phenyl proton of one PPh3 ligand to platinum(II) showing rare intramolecular C–H···Pt anagostic binding interaction. The title complex was determined to be active against tumor cells, and it also showed a moderate inhibitory action against mycobacterium tuberculosis. [ABSTRACT FROM AUTHOR]

Palladium(II) complexes have stimulated research interest mainly due to their in vitro cytotoxicity against various cancer cell lines and their low cytotoxicity in healthy cells. Thus, in this work, we combined Pd(II)/phosphine systems with the natural product curcumin as a ligand, obtaining a series of complexes, [Pd(cur)(PPh 3 ) 2 ]PF 6 (A1), [Pd(cur)(dppe)]PF 6 (A2), [Pd(cur)(dppp)]PF 6 (A3), [Pd(cur)(dppb)]PF 6 (A4) and [Pd(cur)(dppf)]PF 6 (A5), where dppe = 1,2-bis(diphenylphosphino)ethane, dppp = 1,3-bis(diphenylphosphino)propane, dppb = 1,4-bis(diphenylphosphino)butane, and dppf = 1,1'-bis(diphenylphosphino)ferrocene (P-P), which were characterized by elemental analysis, molar conductivity analysis, and mass, NMR ( 1 H, 13 C, 31 P{ 1 H}), UV-vis, and IR spectroscopies, and four of them (A1, A2, A4, and A5) by X-ray crystallography. The in vitro cell viability of the complexes A1-A5, cisplatin, and the free ligand curcumin against MDA-MB-231 (human triple-negative breast tumor cells), SK-BR-3 (human breast tumor cells), A549 (human lung tumor cells), MRC-5 (non-tumor human lung cells), A2780 (human ovarian carcinoma cells), and A2780cis (cisplatin-resistant human ovarian carcinoma cells), was evaluated by the MTT colorimetric assay. For the tumor cell lines tested, the complexes showed good anticancer activities. The results showed that in general the complexes had lower IC 50 values than free curcumin and the precursors [PdCl 2 (P-P)]. IC 50 results obtained for the A1-A5 complexes, in the MCF-7 cell line, are similar to those that had already been observed for some Pd/bipy/curcumin complexes. In the MDA-MB-231 cell line, complexes A1 and A5 stood out, with their lowest IC 50 values, around 5 μmol L -1 , and the complexes appeared to be more active (lower IC 50 values) against the ovarian cell lines. Complex A1 was 23 and 22-fold more cytotoxic than cisplatin, against the A2780 and A2780cis cells, respectively. The complex A1 was studied on A2780cis cells and it was found that this complex inhibits colony formation and induces cell cycle arrest in the sub-G1 phase in a concentration-dependent manner and leads to cell death by apoptosis. The DCFDA assay revealed a potent ROS induction for complex A1.

Copper nitrite reductase mimetics were synthesized using three new tridentate ligands sharing the same N , N , N motif of coordination. The ligands were based on L-proline modifications, attaching a pyridine and a triazole to the pyrrolidine ring, and differ by a pendant group (R = phenyl, n -butyl and n -propan-1-ol). All complexes coordinate nitrite, as evidenced by cyclic voltammetry, UV-Vis, FTIR and electron paramagnetic resonance (EPR) spectroscopies. The coordination mode of nitrite was assigned by FTIR and EPR as κ 2 O chelate mode. Upon acidification, EPR experiments indicated a shift from chelate to monodentate κ O mode, and 15 N NMR experiments of a Zn 2+ analogue, suggested that the related Cu(II) nitrous acid complex may be reasonably stable in solution, but in equilibrium with free HONO under non catalytic conditions. Reduction of nitrite to NO was performed both chemically and electrocatalytically, observing the highest catalytic activities for the complex with n -propan-1-ol as pendant group. These results support the hypothesis that a hydrogen bond moiety in the secondary coordination sphere may aid the protonation step.

This manuscript describes the preparation of a new Ru(ii) nitrosylsulphito complex, trans-[Ru(NH 3 ) 4 (isn)(N(O)SO 3 )] + (complex 1), its spectroscopic and structural characterization, photochemistry, and thermal reactivity. Complex 1 was obtained by the reaction of sulfite ions (SO 3 2- ) with the nitrosyl complex trans-[Ru(NH 3 ) 4 (isn)(NO)] 3+ (complex 2) in aqueous solution resulting in the formation of the N-bonded nitrosylsulphito (N(O)SO 3 ) ligand. To the best of our knowledge, only four nitrosylsulphito metal complexes have been described so far (J. Chem. Soc., Dalton Trans., 1983, 2465-2472), and there is no information about the photochemistry of such complexes. Complex 1 was characterized by spectroscopic means (UV-Vis, EPR, FT-IR, 1 H- and 15 N-NMR), elemental analysis and single-crystal X-ray diffraction. The X-ray structure of the precursor complex 2 is also discussed in the manuscript and is used as a reference for comparisons with the structure of 1. Complex 1 is water-soluble and kinetically stable at pH 7.4, with a first-order rate constant of 3.1 × 10 -5 s -1 for isn labilization at 298 K (t 1/2 ∼ 373 min). Under acidic conditions (1.0 M trifluoroacetic acid), 1 is stoichiometrically converted into the precursor complex 2. The reaction of hydroxide ions (OH - ) with 1 and with 2 yields the Ru(ii) nitro complex trans-[Ru(NH 3 ) 4 (isn)(NO 2 )] + with second-order rate constants of 2.1 and 10.5 M -1 s -1 (at 288 K), respectively, showing the nucleophilic attack of OH - at the nitrosyl in 2 (Ru-NO) and at the nitrosylsulphito in 1 (Ru-N(O)SO 3 ). The pK a value of the -SO 3 moiety of the N(O)SO 3 ligand in 1 was determined to be 5.08 ± 0.06 (at 298 K). The unprecedented photochemistry of a nitrosylsulphito complex is investigated in detail with 1. The proposed mechanism is based on experimental (UV-Vis, EPR, NMR and Transient Absorption Laser Flash Photolysis) and theoretical data (DFT) and involves photorelease of the N(O)SO 3 - ligand followed by formation of nitric oxide (NO˙) and sulfite radicals (SO 3 ˙ - , sulfur trioxide anion radical).