Synthesis,crystal structure and magnetic characterization of a novel linear trinuclear copper(II) complex bridged by phenoxy and benzyloxy oxygen atoms

A novel linear trinuclear copper(II) complex bridged by phenoxy and benzyloxy oxygen atoms ([Cu₃L₂](ClO₄)₂ · (CH₃CN)₂, L = C₁₁H₁₃BrN₂O₂ ²⁻) was synthesized and the crystal structure of the complex was determined by X-ray diffraction technique. The crystal structure of the complex contains a linear trinuclear array of copper(II) ions in which the central copper(II) ion is in an octahedron coordination sphere and lies on an inversion center of the molecule, the terminal ones are in an identical square pyramid structure. Variable-temperature magnetic data indicate that the complex displays a strong antiferromagnetic coupling with J = −270(8) cm⁻¹ between the metal ions.     

Synthesis,crystal structure,and magnetic properties of a linear trinuclear Cu(II) complex

A new linear trinuclear Cu(II) complex, [Cu₃(NTA)₂(4,4′-bpt)₄(H₂O)₂]?·?10H₂O (H₃NTA?=?nitrilotriacetic acid, 4,4′-bpt?=?4-amino-3,5-bis(4-pyridyl)-1,2,4-triazole) (1), was obtained from evaporation of an aqueous solution containing Cu(NO₃)₂?·?6H₂O, 4,4′-bpt, nitrilotriacetic acid (H₃NTA), and NaOH. 1 was characterized using single-crystal X-ray diffraction, IR, and elemental analysis. In the trimer, the three linear copper ions are bridged by two NTA carboxylate groups in a syn–anti conformation and connected by 4,4′-bpt to produce a 1-D array. Temperature-dependent magnetic susceptibilities reveal the presence of weak antiferromagnetic exchange between metal centers.     

Synthesis and studies of a trinuclear Mn(II) carboxylate complex

We report a carboxylate triangle consisting of three manganese(II) centres which is made from manganese(II) carbonate and pivalic acid. The magnetic exchange within the triangle is extremely weak, and antiferromagnetic. Several models have been used to fit the magnetic data, and the best fit uses two weak antiferromagnetic coupling constants of J(1)=-0.588 cm(-1) and J(2)=-0.855 cm(-1). Exchange interactions between the metal centres has been calculated using DFT adopting all the three possible Heisenberg models for a trinuclear system and the results are compared with experimental values. Spin density distribution is used to analyse the nature of the coupling between the metal centres. EPR spectroscopy has been used to explore the nature of the ground state. Recrystallisation of the trinuclear compound from MeCN gives a polymer, while oxidation in air leads to a known compound--an edge-sharing bitetrahedral (MnIII2MnII4) cage.     

Synthesis, characterization, and in vitro evaluation of a potentially selective anticancer, mixed-metal [ruthenium(III)-platinum(II)] trinuclear complex

A new type of mixed-metal trinuclear complex containing platinum(II) and ruthenium(III) fragments that resemble both cisplatin and NAMI-A has been synthesized and characterized by IR, 1H NMR, elemental analysis, and X-ray crystallography. The water-soluble compound Na2{trans,cis,trans-[RuIIICl4(DMSO-S)(mu-pyz)]2PtIICl2} (AH-197, pyz = pyrazine) was assessed for its effects on DNA mobility and toxicity against human cancer cell lines. When compared to cisplatin and KP-1019 (which structurally resembles NAMI-A), IC50 results showed that AH-197 had an intermediate toxicity. When this data was coupled with a subsequent COMPARE evaluation (standard COMPARE queries resulted in insignificant correlation coefficients (<0.70) while very low COMPARE correlation coefficients were found in the matrix queries as well), AH-197 yielded a correlation coefficient of 0.19 when compared to cisplatin and 0.25 when compared to KP1019 indicating that AH-197 has a unique behavior.     

Synthesis,characterization and RNA-binding properties of a novel ruthenium(II) complex coordinated by 5-pyridine-10,15,20-triphenylporphyrin

A novel ruthenium(II) complex, [dibipyridyl-(5-pyridine-10,15,20-tri-phenylporphyrin)] ruthenium(II) chloride, (1), has been synthesized and characterized by elementary analyzing, ESI-MS and ¹³C-NMR, as well as spectroscopy. The electronic spectra and emission spectra have been utilized to study the interaction of this ruthenium(II) complex (1) with the total RNA of liver cells, and the results show that there was obviously hypochromism and a red shift was observed for the Soret absorption and IL transition in electronic spectra of ruthenium(II) complex (1) in the presence of total RNA of liver cells, and the hypochromism of Soret absorption and IL absorption of complex (1) is 25% and 10%, respectively. The studies on the steady-state emission spectra of complex (1) show that the fluorescent of (1) in the 550–700 nm range increased obviously in the presence of total RNA of liver cells. These data, together with that of electronic spectra, shown that the ruthenium(II) complex (1) can bind to RNA excellently.     

A ruthenium(II) complex with the propionate ion: Synthesis,characterization and cytotoxic activity

The complex [Ru(η²-O₂CCH₂CH₃)(dppe)₂]PF₆ (dppe = 1,2-bis(diphenylphosphino)ethane) was prepared and characterized by elemental analysis, spectroscopic techniques, X-ray crystallography, HRESIMS and HRESIMS/MS. The characterization data are consistent with a cis arrangement for the dppe ligands and a bidentate coordination of the propionate ligand through carboxylate oxygens. Cytotoxicity assays were carried out on human and murine cancer and normal cell lines. In general, the [Ru(η²-O₂CCH₂CH₃)(dppe)₂]PF₆ complex was more cytotoxic than both its precursor cis–[RuCl₂(dppe)₂] and the reference metallodrug cisplatin. The best results against the HepG2 human tumour cell line and S180 murine tumour cell line were found with IC₅₀ values of 6.5 ± 0.2 and 0.18 ± 0.03 μM, respectively.     

Synthesis and characterization of some novel ruthenium(II) complexes containing thiolate ligands

Reactions of the ruthenium complexes [RuH(CO)Cl(PPh₃)₃] and [RuCl₂(PPh₃)₃] with hetero-difunctional S,N-donor ligands 2-mercapto-5-methyl-1,3,5-thiadiazole (HL¹), 2-mercapto-4-methyl-5-thiazoleacetic acid (HL²), and 2-mercaptobenzothiazole (HL³) have been investigated. Neutral complexes [RuCl(CO)(PPh₃)₂(HL¹)] (1), [RuCl(CO)(PPh₃)₂(HL²)] (2), [RuCl(CO)(PPh₃)₂(HL³)] (3), [Ru(PPh₃)₂(HL¹)₂] (4), [RuCl(PPh₃)₃(HL²)] (5), and [RuCl(PPh₃)₃(HL³)] (6) imparting κ²-S,N-bonded ligands have been isolated from these reactions. Complexes 1 and 4 reacted with diphenyl-2-pyridylphosphine (PPh₂Py) to give neutral κ¹-P bonded complexes [RuCl(CO)(κ¹-P-PPh₂Py)₂(HL¹)] (7), and [Ru(κ¹-P-PPh₂Py)₂(HL¹)₂] (8). Complexes 1-8 have been characterized by analytical, spectral (IR, NMR, and electronic absorption) and electrochemical studies. Molecular structures of 1, 2, 4, and 7 have been determined crystallographically. Crystal structure determination revealed coordination of the mercapto-thiadiazole ligands (HL¹-HL³) to ruthenium as κ²-N,S-thiolates and presence of rare intermolecular S-S weak bonding interaction in complex 1.     

Synthesis and characterization of a mononuclear ruthenium(III) triazole complex

A mononuclear ruthenium(III) complex containing ethylenediaminetetraacetate (edta), [Ru(Hedta)(Htrz)] · 4H₂O (1) (Htrz = 1H-1,2,4-triazole), has been synthesized and the structure was determined by single-crystal X-ray diffraction. The complex crystallizes in the triclinic space group P 1, with the unit cell parameters a = 7.212(3) Å, b = 9.873(4) Å, c = 13.806(6) Å, α = 91.945(6)°, β = 100.078(6)°, γ = 97.230(7) and Z = 2. The complex was also characterized by elemental analysis, IR, UV–Vis and ESR spectra. Cyclic voltammetry for the complex shows a ruthenium(III)/ruthenium(IV) oxidation and a ruthenium(III)/ruthenium(II) reduction within the range of ?1.5–0.5 V. Magnetic susceptibility data give an effective moment of 1.81 B.M. at room temperature.     

Synthesis and characterization of ruthenium(II) molecular assemblies for photosensitization of nanocrystalline TiO2: utilization of hydroxyl grafting mode

New Ru polypyridine complexes [(bpy)2Ru(L)]2+, where bpy = 2,2'-bipyridine and L = dipyrido[3,2-a:2',3'-c]-phenazine-2-carboxylic acid (dppzc), dipyrido[3,2-f:2',3'-h]quinoxaline-2,3-dicarboxylic acid (dpq(COOH)2), 3-hydroxydipyrido[3,2-f:2',3'-h]quinoxaline-2-carboxylic acid (dpq(OHCOOH)), 2,3-dihydroxydipyrido[3,2-f:2',3'-h]quinoxaline (dpq(OH)2), and [(L')Ru(dppzc)2]2+, where L' = bpy and 1,10-phenanthroline (phen), have been synthesized, characterized, and anchored to nanocrystalline TiO2 electrodes for light to electrical energy conversion in regenerative photoelectrochemical cells with I-/I2 acetonitrile electrolyte. These sensitizers have intense metal-to-ligand charge-transfer (MLCT) bands centered at approximately 450 nm. The effect of pH on the absorption and emission spectra of these complexes consisting of protonatable ligands has been investigated in water by spectrophotometric titration. The excited-state pKa values are more basic than the ground-state ones, except the pKa2 and pKa2* in [(bpy)2Ru(dpq(OH)2)]2+, which are equal, suggesting the localization of the lowest-energy MLCT on heteroaromatic bridging ligands, dppzc and dpq. Incident photon-to-current conversion efficiency (IPCE) is sensitive to the structural changes that resulted from introducing different functional groups, used for grafting.     

A linear trinuclear cobalt(II) complex with 4-(2-pyridine)-1,2,4-triazole: synthesis,structure and characterization

The linear trinuclear cobalt(II) complex [Co₃(pytrz)₆(H₂O)₆](NO₃)₆ (1) with pytrz = 4-(2-pyridine)-1,2,4-triazole has been prepared and characterized. It crystallizes in the rhombohedral R-3 space group with Z = 3, a = 13.955(2), b = 13.955(2), c = 28.942(9) Å, γ = 120°, V = 4881.2(18) ų. The structure of 1 comprises the cation [Co₃(pytrz)₆(H₂O)₆]⁶⁺, in which linear trinuclear Co(II) units are bridged by six L ligands and have six aqua molecules as terminal ligands. The six free nitrates link the terminal aqua ligands through N–H ··· O hydrogen bonds with C₃ symmetry. 1 was characterized by FT-IR, electronic spectra and magnetic measurements. The variable-temperature magnetic measurements reveal weak anti-ferromagnetic interactions in 1.     

Synthesis,spectroscopic and structural characterization of new complex of ruthenium(II) with Hmtpo ligand

The [(PPh₃)₂RuHCl(CO)(Hmtpo)] complex has been prepared and studied by IR, NMR, UV–VIS spectroscopy and X-ray crystallography. The complex was prepared in reactions of [RuHCl(CO)(PPh₃)₃] with 7-hydroxy-5-methyl[1,2,4]triazolo[1,5-a]pyrimidine in methanol. The electronic structure and UV–Vis spectrum of the obtained compound have been calculated using the TD–DFT method.     

Synthesis and characterization of a platinum(II) complex with N-acetyl-L-cysteine

Synthesis and spectroscopic studies in the solid-state of a platinum(II) complex with N-acetyl-L-cysteine are described. Elemental analyses are consistent with composition Pt₂(C₅H₈NO₃S)₄ · 3H₂O. Solid-state ¹³C NMR, infrared, and U-Vis spectroscopic results are consistent with coordination of the ligand to platinum(II) through sulfur. Thermal analyses confirmed water in the complex composition. Final residue of the thermal treatment was identified by powder X-ray diffractometry as metallic platinum.     

Synthesis and photoelectrochemical properties of cyclometallated ruthenium(II) complex

A new ruthenium complex, (4-carboxy-1,10-phenantroline-7-carboxylate)(4,7-dicarboxy-1,10-phenantroline)(2-phenylpyridino-²C,N) ruthenium(II), was obtained for the application as a sensitizer in photoelectrochemical converters (PECC). Electrochemical and spectral characteristics of the compound were studied. It was found that the illumination of PECC with AM 1.5 100 mW/cm² solar spectrum simulator provides short circuit current density of 3.9 mA cm^?2 and broken circuit voltage of 0.47 V. PECC efficiency is 1.4% at fillfactor 76%. The lifetimes of charge carriers (electrons) and their transit time determined by modulation spectroscopy were found to be 28 and 4 ms, respectively.     

Thiolato-bridged RuIIAgIRuII trinuclear complex composed of bis(bipyridine)ruthenium(II) units with chelating 2-aminoethanethiolate: conversion to a disulfide-bridged RuIIRuII dinuclear complex

The reaction of [Ru(solvent)2(bpy)2]2+ (bpy = 2,2'-bipyridine) with Haet (2-aminoethanethiol) in ethanol/water in the presence of Ag+ gave a thiolato-bridged RuIIAgIRuII trinuclear complex, [Ag{Ru(aet)(bpy)2}2]3+, in which two [RuII(aet)(bpy)2]+ units are linked by an AgI atom. When this complex was treated with HCl in acetonitrile/water, a disulfide-bridged RuIIRuII dinuclear complex, [Ru2(cysta)(bpy)4]4+ (cysta = cystamine), was produced as a result of the removal of an AgI atom and the autoxidation of thiolato groups. It was found that the dinuclear structure in [Ru2(cysta)(bpy)4]4+ is reverted back to [Ag{Ru(aet)(bpy)2}2]3+ by treatment with Ag+ assisted by Zn reduction.     

Studies on the interactions of a novel ruthenium(II) complex with G-quadruplex DNA

A novel ruthenium(II) porphyrin complex, [Ru(phen)₂MPyTPP] (phen = phenanthroline, MPyTPP = mono-(3′-Pyridine)-10,15,20-triphenyl porphyrin), has been prepared and characterized by elemental analysis, ESI-MS and NMR methods. The interaction of the complex with G-quadruplex DNA has been studied by spectroscopy, and the results have shown that [Ru(phen)₂MPyTPP] can bind to G-quadruplex d(TTAGGG)₄ with high affinity. In the presence of d(TTAGGG)₄, the characteristic Soret and intra-ligand (IL) transitions in the UV–Vis spectrum of the complex exhibit hypochromism of 25% (Δλ = 6 nm) and 18% (Δλ = 1 nm), respectively. The intrinsic binding constant was calculated according to the decay of the Soret band as 3.02(±0.08) × 10⁶ M⁻¹. The positive signal of d(TTAGGG)₄ in its circular dichroism spectra was clearly decreased in the presence of the complex, indicating the conformation of the G-quadruplex was severely disturbed by the ruthenium(II) complex. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Synthesis,characterization and bioactivity of a new Fe(III) 18-metallacrown-6 and a new trinuclear linear Ni(II) complexes

A new trinuclear linear Ni(II) compound [Ni₃(H₂O)₂(DMA)₂(acshz)₂] · 2DMF (DMA = dimethylamine) (1) and a new Fe(III) 18-metallacrown-6 [Fe₆(acbshz)₆(DMF)(H₂O)₅] · 5DMF (2), with two similar pentadentate ligands, N-acryloyl-salicylhydrazide (H₃acshz) and N-acryloyl-5-bromosalicylhydrazide (H₃acbshz) have been synthesized and characterized by X-ray crystallography. In compound 1, three nickel ions arrange in a strictly linear structure, adjacent molecules are linked by intermolecular H bonds to form a 2D infinite wave-like structure. In compound 2, the ring of the metallacrown is consisted of six interlink [Fe–N–N] repeated units through hydrazide N–N group bridging. It is the first metallacrown that the coordination environments of metal ions in the cycle ring are different, and these differences make the two faces of the disc-shaped hexanuclear ring do not have opposite chiralities. The studies in solution integrity and stability of the metallacrown 2 show it is soluble and stable in DMF. UV–Vis titrations demonstrate the metallacrown 2 is stable in DMF even in the presence of excess metal ions. Antibacterial screening data indicate the two compounds all have antimicrobial activities against the tested microorganisms. The activities of metallacrown 2 are stronger than trinuclear compound 1.     

Synthesis and characterization of tris(bipyridyl)ruthenium(II)-modified mono-, di-, and trinuclear manganese complexes as electron-transfer models for photosystem II

With the aim of modeling the arrangement of redox-active and photoactive components along the electron-transfer pathway of photosystem II, tetra- to nonanuclear transition metal complexes have been synthesized, comprising one, two, or three manganese ions, oxidizable phenolates, and tris(2,2'-bipyridyl)ruthenium(II)-type units as photosensitizers. These model complexes are considered to be mononuclear ([LnMn](PF6)m), dinuclear ([L1aMnIV2(mu-O)2](PF6)6), or trinuclear ([LnMnIIMnIIMnIILn](PF6)12) with respect to the number of manganese centers present. Electronic coupling between the manganese ions is strongly antiferromagnetic in the case of the di(mu-oxo)-dimanganese compound [L1aMnIV2(mu-O)2](PF6)6, where the "ligand" [H2L1a]4+ consists of two tris(bipyridyl)ruthenium(II)-type units covalentely bound to a bismacrocyclic Me2dtne backbone to which the manganese ions are coordinated via an additional phenolate oxygen (Me2dtne = 1,2-bis(4-methyl-1,4,7-triazacyclononyl)ethane). Weak antiferromagnetic coupling is observed in compounds [LnMnIIMnIIMnIILn](PF6)12, where the three metals are in a linear arrangement (face-sharing octahedral). They are bridged by three phenolate oxygens of each of the deprotonated "ligands" [H3Ln]6+, respectively. Each ligand [H3Ln]6+ (n = 1, 2) consists of a tacn ring with three pendent arm phenols which are each bound to a tris(bipyridyl)ruthenium(II)-type unit (tacn = 1,4,7-triazacyclononane). In these compounds several electron-transfer steps were detected by electrochemical methods which are assigned to different redox processes located at individual electrochemically active components (Mn, Ru, bipyridyl, phenolate). For example, in the "mononuclear" compounds [LnMn](PF6)m (n = 1 or 2) Mn(II), Mn(III), and Mn(IV) are accessible and three Ru(II) centers are reversibly oxidized to Ru(III), and in addition, the coordinated phenolate can be oxidized to a highly reactive, coordinated phenoxyl radical. In several cases very slow heterogeneous electron-transfer rates were observed for redox processes involving the manganese centers.     

A ruthenium(II)-trithiacyclononane curcuminate complex: Synthesis,characterization, DNA-interaction,and cytotoxic activity

The coordination of ruthenium(II) complexes to anionic oxygen-based donors are very rare. This study describes a simple, one-pot method for obtaining [ruthenium(II)(trithiacyclononane)(curcumin)(S-DMSO)]Cl (1) in 37% yield. The structural characterization of complex 1 by elemental analysis, FT-IR, 1-D and 2-D NMR, ESI⁺-MS as well as UV–vis and fluorescence spectroscopies are presented. The DNA-melting temperature (T_m) assay shows that salmon sperm DNA (smDNA) in the presence of complex 1 has a higher melting temperature, with ΔT_m = 7.4 °C, while in the presence of curcumin the melting temperature remains unaltered. The in vitro cytotoxic activities of curcumin and complex 1 were investigated using the tumor human prostate cell line, PC-3, and the healthy cell line, PNT-2. Complex 1 is innocuous toward normal prostate epithelial cells and, whereas curcumin is toxic, with inhibition rates of ca. 35 and 65% at 50 and 80 μM, respectively. On the tumor cell line PC-3, complex 1 did not cause viability changes, whereas curcumin exhibited dose-dependent inhibition, with ca. 73% inhibition at the highest concentration tested, i.e. 80 μM. This study suggests that coordination with the trithiacyclononane ruthenium(II) scaffold stabilizes the photochemical properties of curcumin and strongly changes its biologic activity.