Chlorido Ligands Research Articles

Copper(II) and Zinc(II) Complexes with the Clinically Used Fluconazole: Comparison of Antifungal Activity and Therapeutic Potential.

Copper(II) and zinc(II) complexes with clinically used antifungal drug fluconazole (fcz), {[CuCl2(fcz)2].5H2O}n, 1, and {[ZnCl2(fcz)2]·2C2H5OH}n, 2, were prepared and characterized by spectroscopic and crystallographic methods. The polymeric structure of the complexes comprises four fluconazole molecules monodentately coordinated via the triazole nitrogen and two chlorido ligands. With respect to fluconazole, complex 2 showed significantly higher antifungal activity against Candida krusei and Candida parapsilosis. All tested compounds reduced the total amount of ergosterol at subinhibitory concentrations, indicating that the mode of activity of fluconazole was retained within the complexes, which was corroborated via molecular docking with cytochrome P450 sterol 14α-demethylase (CYP51) as a target. Electrostatic, steric and internal energy interactions between the complexes and enzyme showed that 2 has higher binding potency to this target. Both complexes showed strong inhibition of C. albicans filamentation and biofilm formation at subinhibitory concentrations, with 2 being able to reduce the adherence of C. albicans to A549 cells in vitro. Complex 2 was able to reduce pyocyanin production in Pseudomonas aeruginosa between 10% and 25% and to inhibit its biofilm formation by 20% in comparison to the untreated control. These results suggest that complex 2 may be further examined in the mixed Candida-P. aeruginosa infections.

Magnetostructural study of four-coordinated Co(II) complexes with mixed ligand surrounding

The dependence of the zero-field splitting parameters on the structural modification of the nearest ligands surrounding in the [CoCl2L2] complexes (with L being the N-donor ligand) is studied. The modification was modeled by the variations of the NCoN and ClCoCl angles, by the rotation of the chlorido ligands with respect to other ligand groups as well as by the strength of the N-donor ligands. The found tendency was compared with the experimental data for this type of cobalt complexes known from literature.

A Combined Spectroscopic and Protein Crystallography Study Reveals Protein Interactions of RhI(NHC) Complexes at the Molecular Level.

While most Rh-N-heterocyclic carbene (NHC) complexes currently investigated in anticancer research contain a Rh(III) metal center, an increasing amount of research is focusing on the cytotoxic activity and mode of action of square-planar [RhCl(COD)(NHC)] (where COD = 1,5-cyclooctadiene) which contains a Rh(I) center. The enzyme thioredoxin reductase (TrxR) and the protein albumin have been proposed as potential targets, but the molecular processes taking place upon protein interaction remain elusive. Herein, we report the preparation of peptide-conjugated and its nonconjugated parent [RhCl(COD)(NHC)] complexes, an in-depth investigation of both their stability in solution, and a crystallographic study of protein interaction. The organorhodium compounds showed a rapid loss of the COD ligand and slow loss of the NHC ligand in aqueous solution. These ligand exchange reactions were reflected in studies on the interaction with hen egg white lysozyme (HEWL) as a model protein in single-crystal X-ray crystallographic investigations. Upon treatment of HEWL with an amino acid functionalized [RhCl(COD)(NHC)] complex, two distinct rhodium adducts were found initially after 7 d of incubation at His15 and after 4 weeks also at Lys33. In both cases, the COD and chlorido ligands had been substituted with aqua and/or hydroxido ligands. While the histidine (His) adduct also indicated a loss of the NHC ligand, the lysine (Lys) adduct retained the NHC core derived from the amino acid l-histidine. In either case, an octahedral coordination environment of the metal center indicates oxidation to Rh(III). This investigation gives the first insight on the interaction of Rh(I)(NHC) complexes and proteins at the molecular level.

Energetically significant nitrile⋯nitrile and unconventional C–H⋯π(nitrile) interactions in pyridine based Ni(II) and Zn(II) coordination compounds: Antiproliferative evaluation and theoretical studies

Two new coordination compounds viz. [Ni(2,6-PDC)(Hdmpz)(H2O)2]∙H2O (1) and [Zn(3-CNpy)2Cl2] (2) (2,6-PDC = 2,6-pyridinedicarboxylate, Hdmpz = 3,5-dimethylpyrazole, 3-CNpy = 3-cyanopyridine) have been synthesized and characterized using elemental analysis, thermogravimetric analysis, electronic, infrared spectroscopy and single crystal X-ray diffraction techniques. Crystal structure analyses reveal the presence of supramolecular assemblies involving interesting dimers with unconventional contacts in the compounds. DFT (Density Functional Theory) calculations on the supramolecular dimers in the crystal structure of 1 reveal that the sum of contributions of anion–π, π–π and other long range interactions due to the approximation of the bulk monomers is energetically significant. Molecular Electrostatic Potential (MEP) surface and Quantum Theory of Atoms in Molecules (QTAIM) analyses on the interesting supramolecular dimers of the crystal structures of 2 reveal the presence of unconventional anion⋯π contacts involving coordinated chlorido ligands and C–H⋯π(nitrile) interactions involving the π-system of the nitrile moiety of 3-cyanopyridine. Remarkably, Atoms in Molecules analysis also confirms the existence of energetically significant unconventional anti-parallel nitrile⋯nitrile interaction in the crystal structure of 2. Cell cytotoxicity of the compounds performed in Dalton's lymphoma (DL) malignant cancer cell line showed effective potency with negligible cytotoxicity in normal cells (~12%). It is interesting that compound 1has excellent cytotoxic potency with IC50 closer to cisplatin and can bind different biological targets with similar signalling pathways. Structure activity relationship (SAR) analyses of 1 and 2 based on pharmacophore modelling reveal that the molecular features associated with the structures of the compounds play important role in the biological activities.

Synthesis and characterization of a tert-butyl ester-substituted titanocene dichloride: t-BuOOCCp2TiCl2.

Bis[η5-(tert-butoxyca-rbonyl)-cyclo-penta-dien-yl]di-chlorido-titanium(IV), [Ti(C10H13O2)2Cl2], was synthesized from LiCpCOOt-Bu using TiCl4, and was characterized by single-crystal X-ray diffraction and 1H NMR spectroscopy. The distorted tetra-hedral geometry about the central titanium atom is relatively unchanged compared to Cp2TiCl2. The complex exhibits elongation of the titanium-cyclo-penta-dienyl centroid distances [2.074 (3) and 2.070 (3) Å] and a contraction of the titanium-chlorine bond lengths [2.3222 (10) Å and 2.3423 (10) Å] relative to Cp2TiCl2. The dihedral angle formed by the planes of the Cp rings [52.56 (13)°] is smaller than seen in Cp2TiCl2. Both ester groups extend from the same side of the Cp rings, and occur on the same side of the complex as the chlorido ligands. The complex may serve as a convenient synthon for titanocene complexes with carboxyl-ate anchoring groups for binding to metal oxide substrates.

Markedly different magnetic properties of two analogous Ni(II) complexes with 2-aminoethylpyridine: [Ni(2aepy)2Cl(H2O)]Cl⋅H2O and [Ni(2aepy)2(NO3)]NO3

By the reaction of nickel(II) chloride hexahydrate and nickel(II) nitrate hexahydrate with 2-aminoethylpyridine (2aepy) in the molar ratio 1:2 two complexes were isolated, namely [Ni(2aepy)2Cl(H2O)]Cl⋅H2O (1) and [Ni(2aepy)2(NO3)]NO3 (2). In both ionic complexes hexacoordinated Ni(II) central atoms exhibit heteroleptic coordination sphere formed by two chelate bonded 2aepy ligands and the remaining two coordination sites in cis positions are occupied by co-ligand(s), aqua and chlorido ligands in 1 and chelate bonded nitrato ligand in 2. In both crystal structures 1 and 2, medium strength hydrogen bonds led to formation of 2D hydrogen-bonded supramolecular structures. The study of the magnetic response in the temperature range 1.8–300 K and ab initio calculations in 1 revealed that the system can be considered as a rare candidate to study the behavior of anisotropic S = 1 antiferromagnetic spin chain close to the quantum-critical point defined by the ratio of the single-ion anisotropy and exchange interaction, which was estimated as D/J = 1.14 for 1. On the other hand, the coordination of nitrate ligand to the central Ni(II) ion in 2 yields a substantial change of the nature of anisotropy from easy-plane to easy-axis type with D/kB = −5.7 K and suppression of the exchange interaction between the Ni(II) centers.

Solvent Effect on the Regulation of Urea Hydrolysis Reactions by Copper Complexes

Abiotic allosterism is most commonly observed in hetero-bimetallic supramolecular complexes and less frequently in homo-bimetallic complexes. The use of hemilabile ligands with high synthetic complexity enables the catalytic center by the addition or removal of allosteric effectors and simplicity is unusually seen in these systems. Here we describe a simpler approach to achieve kinetic regulation by the use of dimeric Schiff base copper complexes connected by a chlorido ligand bridge. The chlorido ligand acts as a weak link between monomers, generating homo-bimetallic self-aggregating supramolecular complexes that generate monomeric species in different reaction rates depending on the solvent and on the radical moiety of the ligand. The ligand exchange was observed by electron paramagnetic resonance (EPR) and conductivity measurements, indicating that complexes with ligands bearing methoxyl (CuIIL2) and ethoxyl (CuIIL5) radicals were more prone to form dimeric complexes in comparison to ligands bearing hydrogen (CuIIL1), methyl (CuIIL3), or t-butyl (CuIIL4) radicals. The equilibrium between dimer and monomer afforded different reactivities of the complexes in acetonitrile/water and methanol/water mixtures toward urea hydrolysis as a model reaction. It was evident that the dimeric species were inactive and that by increasing the water concentration in the reaction medium, the dimeric structures dissociated to form the active monomeric structures. This behavior was more pronounced when methanol/water mixtures were employed due to a slower displacement of the chlorido bridge in this medium than in the acetonitrile/water mixtures, enabling the reaction kinetics to be evaluated. This effect was attributed to the preferential solvation shell by the organic solvents and in essence, an upregulation behavior was observed due to the intrinsic nature of the complexes to form dimeric structures in solution that could be dismantled in the presence of water, indicating their possible use as water-sensors in organic solvents.

Synthesis, characterization and crystal structures of platinum(II) saccharinate complexes with 1,5-cyclooctadiene

Two new platinum(II) complexes, namely [PtCl(sac)(COD)] (1) and [Pt(sac)2(COD)] (2) (sac = saccharinate and COD = 1,5-cyclooctadiene), were synthesized and characterized by elemental analysis, IR, NMR, ESI-MS spectroscopic and thermal analysis (TG/DTA) methods. The platinum(II) complexes were prepared from the reaction of [PtCl2(COD)] with Na(sac)•2H2O. The addition of the sac ligand resulted in the replacement of 1 and 2 chlorido ligands in [PtCl2(COD)] to yield 1 and 2, respectively. The structures of the complexes were determined by single crystal X-ray diffraction and showed a distorted square planar coordination geometry around platinum(II). COD acted as a π-donor ligand, while sac was N -coordinated in both complexes. The TG/DTA data indicated that both complexes were thermally stable up to 220 °C in air and their thermal decompositions yielded Pt as a final product. Complexes 1 and 2 were also designed as possible precursors to synthesize new mixed-ligand platinum(II) sac complexes in a one-pot reaction.

Influence of graphene sheet properties as supports of iridium-based N-heterocyclic carbene hybrid materials for water oxidation electrocatalysis

The effect of the structural properties of graphene materials on the local structure of –OH anchored Ir(I)–NHC complexes is herein investigated. For that, two partially reduced graphene oxides exhibiting different sheet properties due to an adequate selection of the crystalline characteristics of their parent graphite were used. The main differences among them were the size of Csp2 domains within their graphenic layers and the distribution of functional groups at the basal planes and edges. Anchoring of N-methylimidazolium moieties through the graphene –OH functional groups and subsequent formation of the Ir(I)–NHC complexes resulted in graphene-based hybrid materials. The structural differences of the support have an influence in the interaction of the supported iridium compounds with the graphene sheet. The oxygenated functional groups in the material with a smaller graphene sheet are closer leaving larger Csp2 domains in the graphene layer, favoring their interaction with the supported iridium atoms therefore displacing the chlorido ligand from the first coordination shell. In contrast, the hybrid material in which the distribution of the oxygenated functional groups within the basal planes of the graphenic layer is more homogeneous shows partial chlorido displacement. This fact has an influence on the electrocatalytic performance of the iridium-based hybrid materials as water oxidation catalysts (WOCs), exhibiting improved catalytic activity the catalyst having coordinated chlorido ligands.

Platinum(IV) Complexes of trans-1,2-diamino-4-cyclohexene: Prodrugs Affording an Oxaliplatin Analogue that Overcomes Cancer Resistance.

Six platinum(IV) compounds derived from an oxaliplatin analogue containing the unsaturated cyclic diamine trans-1,2-diamino-4-cyclohexene (DACHEX), in place of the 1,2-diaminocyclohexane, and a range of axial ligands, were synthesized and characterized. The derivatives with at least one axial chlorido ligand demonstrated solvent-assisted photoreduction. The electrochemical redox behavior was investigated by cyclic voltammetry; all compounds showed reduction potentials suitable for activation in vivo. X-ray photoelectron spectroscopy (XPS) data indicated an X-ray-induced surface reduction of the Pt(IV) substrates, which correlates with the reduction potentials measured by cyclic voltammetry. The cytotoxic activity was assessed in vitro on a panel of human cancer cell lines, also including oxaliplatin-resistant cancer cells, and compared with that of the reference compounds cisplatin and oxaliplatin; all IC50 values were remarkably lower than those elicited by cisplatin and somewhat lower than those of oxaliplatin. Compared to the other Pt(IV) compounds of the series, the bis-benzoate derivative was by far (5–8 times) the most cytotoxic showing that low reduction potential and high lipophilicity are essential for good cytotoxicity. Interestingly, all the complexes proved to be more active than cisplatin and oxaliplatin even in three-dimensional spheroids of A431 human cervical cancer cells.

Iridium(III) coordination of N(6) modified adenine derivatives with aminoacid chains

In this manuscript we report the preparation of three N6-aminoacid-adenine-derivatives: N-(7H-purin-6-yl)glycine·0.5H2O (N6-GlyAde), N-(7H-purin-6-yl)-β-alanine·1.5H2O (N6-β-AlaAde) and N-(7H-purin-6-yl)-γ-aminobutyric·2H2O (N6-GabaAde) and the synthesis and X-ray characterization of three Ir(III) NAMI-A derivatives (NAMI-A is [imidazoleH][trans-RuIIICl4(DMSO-κS)(imidazole)]) [trans-IrIIICl4(DMSO-κS)(N3-H)-(7H-purin-6-yl)glycine-κN9] (1), [trans-IrIIICl4(DMSO-κS)(N3-H)-(7H-purin-6-yl)-β-alanine-κN9] hydrate (2) and [trans-IrIIICl4(DMSO-κS)(N3-H)-(7H-purin-6-yl)-γ-aminobutyryl-κN9] (3). In all complexes the metal center shows octahedral geometry with coordination to four chlorido ligands and one S coordinated dimethylsulfoxide (DMSO-κS). The coordination sphere of the metal is completed by the modified adenine molecule which is bound via N(9) and protonated at N(3). In two complexes the importance of lone pair (lp)–π interactions involving the adenine ring have been studied using density functional theory (DFT) calculations and the Bader's theory of atoms in molecules. Furthermore, the ability of complexes (1–3) to affect the cell viability was evaluated against three different cancer cell lines: human lung carcinoma cells (A549), human cervical carcinoma cells (HeLa) and human breast cancer cells (MCF7). We have also analyzed their ability to cleave the DNA experimentally and their affinity for two models of DNA has been studied using molecular docking simulations.

Crystal structures of chlorido-[dihy-droxybis-(1-imino-eth-oxy)]arsanido-κ3 N,As,N']platinum(II) and of a polymorph of chlorido-[dihy-droxybis-(1-imino-prop-oxy)arsanido-κ3 N,As,N']platinum(II).

Each central platinum(II) atom in the crystal structures of chlorido-[dihy-droxybis-(1-imino-eth-oxy)arsanido-κ3 N,As,N']platinum(II), [Pt(C4H10AsN2O4)Cl] (1), and of chlorido-[dihy-droxybis-(1-imino-prop-oxy)arsanido-κ3 N,As,N']platinum(II), [Pt(C6H14AsN2O4)Cl] (2), is coordinated by two nitro-gen donor atoms, a chlorido ligand and to arsenic, which, in turn, is coordinated by two oxygen donor ligands, two hydroxyl ligands and the platinum(II) atom. The square-planar and trigonal-bipyramidal coordination environments around platinum and arsenic, respectively, are significantly distorted with the largest outliers being 173.90 (13) and 106.98 (14)° for platinum and arsenic in (1), and 173.20 (14)° and 94.20 (9)° for (2), respectively. One intra-molecular and four classical inter-molecular hydrogen-bonding inter-actions are observed in the crystal structure of (1), which give rise to an infinite three-dimensional network. A similar situation (one intra-molecular and four classical inter-molecular hydrogen-bonding inter-actions) is observed in the crystal structure of (2). Various π-inter-actions are present in (1) between the platinum(II) atom and the centroid of one of the five-membered rings formed by Pt, As, C, N, O with a distance of 3.7225 (7) Å, and between the centroids of five-membered (Pt, As, C, N, O) rings of neighbouring mol-ecules with distances of 3.7456 (4) and 3.7960 (6) Å. Likewise, weak π-inter-actions are observed in (2) between the platinum(II) atom and the centroid of one of the five-membered rings formed by Pt, As, C, N, O with a distance of 3.8213 (2) Å, as well as between the Cl atom and the centroid of a symmetry-related five-membered ring with a distance of 3.8252 (12) Å. Differences between (2) and the reported polymorph [Miodragović et al. (2013 ▸). Angew. Chem. Int. Ed. 52, 10749-10752] are discussed.

Synthesis, characterization and crystal structures of platinum(II) saccharinate complexes with 1,5-cyclooctadiene.

Two new platinum(II) complexes, namely [PtCl(sac)(COD)] (1) and [Pt(sac)2(COD)] (2) (sac = saccharinate and COD = 1,5-cyclooctadiene), were synthesized and characterized by elemental analysis, IR, NMR, ESI-MS spectroscopic and thermal analysis (TG/DTA) methods. The platinum(II) complexes were prepared from the reaction of [PtCl2(COD)] with Na(sac)•2H2O. The addition of the sac ligand resulted in the replacement of 1 and 2 chlorido ligands in [PtCl2(COD)] to yield 1 and 2, respectively. The structures of the complexes were determined by single crystal X-ray diffraction and showed a distorted square planar coordination geometry around platinum(II). COD acted as a π-donor ligand, while sac was N -coordinated in both complexes. The TG/DTA data indicated that both complexes were thermally stable up to 220 °C in air and their thermal decompositions yielded Pt as a final product. Complexes 1 and 2 were also designed as possible precursors to synthesize new mixed-ligand platinum(II) sac complexes in a one-pot reaction.

Cytotoxic (cis,cis-1,3,5-triaminocyclohexane)ruthenium(II)-diphosphine complexes; evidence for covalent binding and intercalation with DNA.

We report cytotoxic ruthenium(ii) complexes of the general formula [RuCl(cis-tach)(diphosphine)]+ (cis-tach = cis-cis-1,3,5-triaminocyclohexane) that have been characterised by 1H, 13C and 31P{1H} NMR spectroscopy, mass spectrometry, X-ray crystallography and elemental analysis. The kinetics of aquation and stability of the active species have been studied, showing that the chlorido ligand is substituted by water at 298 K with first order rate constants of 10-2-10-3 s-1, ideal for potential clinical use as anti-tumour agents. Strong interactions with biologically relevant duplex and quadruplex DNA models correlate with the activity observed with A549, A2780 and 293T cell lines, and the degree of activity was found to be sensitive to the chelating diphosphine ligand. A label-free ptychographic cell imaging technique recorded cell death processes over 4 days. The Ru(ii) cis-tach diphosphine complexes exhibit anti-proliferative effects, in some cases outperforming cisplatin and other cytotoxic ruthenium complexes.

Isomers in chlorido and alkoxido-substituted oxidorhenium(v) complexes: effects on catalytic epoxidation activity.

The syntheses and characterizations of oxidorhenium(v) complexes trans-dichlorido [ReOCl2(PPh3)(L1a)] (trans-2a), cis-dichlorido [ReOCl2(PPh3)(L1b)] (cis-2b) and ethoxido-complex [ReO(OEt)(L1b)2] (4b), ligated with the dimethyloxazoline-phenol ligands HL1a and HL1b are described. The bidentate ligand HL1a (2-(4,4-dimethyl-4,5-dihydro-1,3-oxazol-2-yl)-phenol) is unsubstituted on the phenol ring; ligand HL1b (2-(4,4-dimethyl-4,5-dihydro-1,3-oxazol-2-yl)-4-nitrophenol) contains a nitro group in para-position to the hydroxy group. In the reaction of precursor complex [ReOCl3(PPh3)2] and HL1a the two stereoisomers cis/trans-2a, with respect to chlorido ligands, are formed. The solid state structures of both isomers cis- and trans-2a were determined by single crystal X-ray diffraction analysis. In contrast, with ligand HL1b, only the cis-isomer cis-2b was obtained. Ethoxido-complex 4b is exclusively obtained when precursor [ReOCl3(OPPh3)(SMe2)] is reacted with 2 equiv. of HL1b in ethanol in the presence of the base 2,6-dimethylpyridine (lutidine). If no lutidine is added, chlorido-complex [ReOCl(L1b)2] (3b) is obtained. Complexes [ReOCl2(PPh3)(L1a)] (cis/trans-2a), [ReOCl2(PPh3)(L1b)] (cis-2b), [ReO(OMe)(L1a)2] (4a) and [ReO(OEt)(L1b)2] (4b) were tested as homogeneous catalysts in the benchmark reaction of cyclooctene epoxidation. The influence of isomerism and effects of ligand substitutions on catalytic activity was investigated. Based on the time-conversion plots it can be concluded that cis/trans-isomerism does not influence catalytic activity, but electron-withdrawing substituents, as in cis-2b, 3b and 4b, show a beneficial effect.

Antitumoral effects of mitochondria-targeting neutral and cationic cis-[bis(1,3-dibenzylimidazol-2-ylidene)Cl(L)]Pt(ii) complexes.

Recently, we opened a synthetic access to antitumoral platinum complexes of the type cis-[(NHC)1(NHC)2PtIICl(L)] which interact with DNA in a way correlated to the complex charge and to the sterical accessibility of the leaving chlorido ligand. We now identified mitochondria rather than nuclei as the cellular target of the neutral dichlorido complex 1 (L = Cl) and the delocalized lipophilic cationic phosphine complex 2 (L = PPh3), both carrying the same cis-bis(1,3-dibenzylimidazol-2-ylidene) ligands. Their uptake into 518A2 melanoma cells was concentration-dependent and distinctly greater for complex 2 which was also more cytotoxic against sensitive cancer cell lines with submicromolar IC50 values. Both complexes interfered strongly with various forms of DNA in vitro, but only complex 2 caused a melanoma cell cycle arrest in G1-phase, setting both apart from the S-phase arresting drug cisplatin. Studies of the intracellular localisation of 1 and 2 were carried out with their alkyne-tagged analogues 6 and 7, which showed identical patterns of cancer cell cytotoxicity, cell cycle interference and effects on mitochondria. Click reactions with 7-hydroxycoumarin azide, colocalisation with Mitotracker™ and confocal microscopy, proved complexes 6 and 7 to accumulate mainly in the mitochondria rather than the nuclei of melanoma cells. Complex 1 and even more so complex 2 reduced the mitochondrial membrane potential and also increased the cellular ROS levels. As a consequence, both complexes caused stress fibre formation in the F-actin cytoskeleton of melanoma cells, most distinctly so complex 2 which also activated the apoptotic cascade mediated by capases-3 and -7.

Framework Conversion of Oxido-Bridged Dinuclear Ruthenium Complexes.

Syntheses, properties, and reactions of hydroxido- or oxido-bridged dinuclear ruthenium complexes bearing a tridentate auxiliary ligand, ethylbis(2-pyridylmethyl)amine (ebpma) or benzylbis(2-pyridylmethyl)amine (bbpma), have been investigated. Reduction reactions of a singly oxido-bridged diruthenium complex bearing ebpma, [{RuIII,IVCl2(ebpma)}2(μ-O)]+ ([2Cl]+), by zinc in acetonitrile afforded an acetonitrile-substituted singly oxido-bridged complex in the RuIII-RuIII isovalent state, [{RuIII,IIICl(NCCH3)(ebpma)}2(μ-O)]2+ ([2CH3CN]2+). Chlorido ligand abstraction reactions using silver salts have also been attempted. Through a reaction of [2Cl]+ with two equimolar amounts of AgNO3 in water-acetone, a singly oxido-bridged complex having an aqua and a hydroxido, [{RuIIICl(OH2)(ebpma)}(μ-O){RuIVCl(OH)(ebpma)}]2+ ([2H2O-OH]2+), was obtained. Reactions with four equimolar amounts of AgL (L = CH3COO- or NO3-) in water-acetone gave doubly oxido- and bidentate oxygen donor ligand-bridged diruthenium complexes of Ru(III)-Ru(IV), [{RuIII,IV(ebpma)}2(μ-O)2(μ-L)]2+ ([3L]2+; L = O2CCH3; [3CH3COO]2+, L = O2NO; [3NO3]2+). Reactions of [3L]2+ under acidic conditions afforded a corresponding one-protonated species having the {Ru2(μ-O)(μ-OH)} core. Reactivity and electronic structure of the oxido-bridged diruthenium complexes were studied by electrochemical, spectroscopic, and theoretical methods.

Trinuclear CoIILnIIICoII Complexes (Ln = La, Ce, Nd, Sm, Gd, Dy, Er, and Yb) with 2,6-Dipicolinoylbis(N,N-diethylthiourea): Synthesis, Structures, and Magnetism.

One-pot reactions of 2,6-dipicolinoylbis(N,N-diethylthiourea) (H2L) with Co(CH3COO)2·4H2O and LnCl3, where Ln = La, Ce, Nd, Sm, Gd, Dy, Er, and Yb, in warm methanol in the presence of Et3N, give stable trinuclear complexes of the composition [LnCo2(L)2(μ1,3-OOCCH3)2X] ("CoLnCo" complexes), where X- = κ2-CH3COO- or Cl-. X-ray structure determinations reveal symmetric trinuclear complexes containing two organic ligands (L2-), two terminal CoII ions, and one central LnIII ion. The organic ligands coordinate equatorially to the two CoII ions via two bidentate (O,S) N-acylthiourea moieties and tridentate to the central Ln ion via the (O,N,O) 2,6-dipicolinoyl moieties. Two acetate bridges established between each of the terminal Co and central Ln ions complete the square-pyramidal coordination spheres of CoII. All products possess an additional chlorido ligand axially coordinated to the lanthanide except the gadolinium(III) and lanthanum(III) complexes, where bidentate acetato ligands are coordinated. Fitting the χmT versus T data of the "CoLaCo" complex gives the axial and rhombic zero-field-splitting parameters D = 24.3(4) cm-1 and E = -1.0(2) cm-1, respectively, and anisotropic Landé values gx,y = 2.81(1) and gz = 2.00 as well as weak antiferromagnetic interactions between two high-spin CoII centers with J = -0.49(2) cm-1. The nature of the magnetic interactions between the LnIII ions and the CoII ions in the "CoLnCo" complexes is deduced by comparing their χMT values to the sum of χMT values of the analogous "CoLaCo" and related "ZnLnZn" complexes. The "CoDyCo" complex reveals an antiferromagnetic interaction, while the remaining "CoLnCo" complexes show ferromagnetic interactions.

Synthesis and Cytotoxicity of Water-Soluble Dual- and Triple-Action Satraplatin Derivatives: Replacement of Equatorial Chlorides of Satraplatin by Acetates.

Pt(II) complexes, such as cisplatin and oxaliplatin, are in widespread use as anticancer drugs. Their use is limited by the toxic side effects and the ability of tumors to develop resistance to the drugs. A popular approach to overcome these drawbacks is to use their kinetically inert octahedral Pt(IV) derivatives that act as prodrugs. The most successful Pt(IV) complex in clinical trials to date is satraplatin, cct-[Pt(NH3)(c-hexylamine)Cl2(OAc)2], that upon cellular reduction releases the cytotoxic cis-[Pt(NH3)(c-hexylamine)Cl2]. In an attempt to obtain water-soluble and more effective cytotoxic Pt(IV) complexes, we prepared a series of dual- and triple-action satraplatin analogues, where the equatorial chlorido ligands were replaced with acetates and the axial ligands include innocent and bioactive ligands. Replacement of the chlorides with acetates enhanced the water solubility of the compounds and, with one exception, all of the compounds were very stable in buffer. In general, compounds with one or two axial hydroxido ligands were reduced by ascorbate significantly more quickly than compounds with two axial carboxylates. While replacement of the chlorides with acetates in satraplatin led to a reduction in cytotoxicity, the dual- and triple-action analogues with equatorial acetates had low- to sub-micromolar IC50 values in a panel of eight cancer cells. The triple-action compound cct-[Pt(NH3)(c-hexylamine)(OAc)2(PhB)(DCA)] was active in all cell lines, causing DNA damage that induced cell cycle inhibition and apoptosis. Its good activity against CT26 cells in vitro translated into good in vivo efficacy against the CT26 allograft, an in vivo model with intrinsic satraplatin resistance. This indicates that multiaction Pt(IV) derivatives of diamine dicarboxylates are interesting anticancer drug candidates.

TcI(NO)X(Cp)(PPh3)] Complexes (X–= I–, I3–, SCN–, CF3SO3–, or CF3COO–) and Their Reactions

Reactions of [Tc(NO)Cl(Cp)(PPh3)] with a series of monodentate ligands X– (X– = I–, I3–, F3CSO3–, CF3COO–, or SCN–) result in a ready replacement of the chlorido ligand and the formation of complexes of the general composition [Tc(NO)X(Cp)(PPh3)]. Technetium retains its oxidation state “+1” and its pseudotetrahedral coordination environment. [Tc(NO)(SCN)(Cp)(PPh3)] is the first technetium complex with an S-coordinated SCN– ligand. The complexes are stable as solids. In solution, however, a slow isomerization of the thiocyanato compound into the thermodynamically more stable isothiocyanato species is observed, while solutions of [Tc(NO)(I3)(Cp)(PPh3)] undergo an internal oxidation under formation of the technetium(II) complex [Tc(NO)(I)2(Cp)]. All products were characterized by elemental analysis, NMR and IR spectroscopy, and X-ray structure analysis. Particularly, 99Tc NMR spectroscopy proved to be a valuable method for these types of technetium(I) compounds.