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 electrochemiluminescent ruthenium(II) complexes containing o-phenanthroline and various alpha-diimine ligands

A series of o-phenanthroline-substituted ruthenium(II) complexes containing 2,2′-dipyridyl, 2-(2-pyridyl)benzimidazole, 2-(2-pyridyl)-N-methylbenzimidazole, 4-carboxymethyl-4′-methyl-2,2′-dipyridyl, and/or 4,4′-dimethyl-2,2′-dipyridyl ligands were synthesized and examined as potent electrochemiluminescent (ECL) materials. The characteristics of these complexes, regarding their electrochemical redox potentials and relative ECL intensities for tripropylamine were studied. As found in a 2,2′-bipyridyl-substituted ruthenium(II) complexes, a good correlation between the observed ECL intensity and the donor ability of α-diimine ligands was observed, i.e., the ECL intensity of the Ru(II) complex decreased with an increase in the ligand donor ability. The ECL efficiency increased as the number of substitutions of o-phenanthroline (o-phen) to metal complexes increased.     

Synthesis,characterization, and catalytic properties of some new ruthenium(II)/(III) complexes containing N,N-donor ligands

This article describes the preparation and characterization of cis-[Ru(bipy)₂L](ClO₄)₂ and trans-[RuCl₂L₂]?·?Cl (bipy?=?2,2′-bipyridyl and L?=?ortho-phenylenediamine (o-phd), 2-aminopyridine (2-apy) and 2-aminobenzonitrile (2-abn), and examines the catalytic oxidations of benzyl alcohol, benzohydrol and pipronyl alcohol by cis-[Ru(bipy)₂ (o-phd)](ClO₄)₂ and trans-[RuCl₂(o-phd)₂]?·?Cl complexes at room temperature and in the presence of N-methyl morpholine-N-oxide (NMO) as co-oxidant.     

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 new metal(II) complexes with formates and some nitrogen donor ligands

New mixed-ligands complexes with empirical formulae: M(2,4′-bpy)₂L₂·H₂O (M(II)Zn, Cd), Zn(2-bpy)₃L₂·4H₂O, Cd(2-bpy)₂L₂·3H₂O, M(phen)L₂·2H₂O (where M(II)=Mn, Ni, Zn, Cd; 2,4′-bpy=2,4′-bipyridine, 2-bpy=2,2′-bipyridine, phen=1,10-phenanthroline, L=HCOO⁻) were prepared in pure solid state. They were characterized by chemical, thermal and X-ray powder diffraction analysis, IR spectroscopy, molar conductance in MeOH, DMF and DMSO. Examinations of OCO⁻ absorption bands suggest versatile coordination behaviour of obtained complexes. The 2,4′-bpy acts as monodentate ligand; 2-bpy and phen as chelating ligands. Thermal studies were performed in static air atmosphere. When the temperature raised the dehydration processes started. The final decomposition products, namely MO (Ni, Zn, Cd) and Mn₃O₄, were identified by X-ray diffraction.     

Synthesis and characterization of cyclometalated iridium(III) complexes containing benzoxazole derivatives and different ancillary ligands

The synthesis, structures, electrochemistry, and photophysics of a series of cyclometalated iridium(III) complexes based on benzoxazole derivatives and different β-diketonate ligands are reported. These complexes have a general formula C^∧N₂Ir(LL′) [where C^∧N is a monoanionic cyclometalating ligand; 2-phenylbenzoxazolato (pbo), 2-(4-chlorophenyl)benzoxazolato (cpbo), 2-phenyl-5-chlorobenzoxazolato (pcbo), 2-(3,5-difluorophenyl)benzoxazole (fpbo), or 2-(2-naphthyl)benzoxazolato (nbo), and LL′ is an ancillary ligand; acetylacetonate (acac), dibenzoylmethanate (dbm), or 1,1,1,5,5,5-hexafluoroacetylacetonate (hfacac)]. The complexes (pcbo)₂Ir(acac) (3), (dfpbo)₂Ir(acac) (4), (cpbo)₂Ir(dbm) (7), (dfpbo)₂Ir(dbm) (8), and (dfpbo)₂Ir(hfacac) (9) have been structurally characterized by X-ray crystallography. All of the complexes show reversible oxidation between 0.45 and 1.07 V, versus Fc/Fc⁺, and have short luminescence lifetime (τ = 0.1-1.3 μs) at room temperature. Except complex 9, the radiative decay rate (k_r) and nonradiative decay rate (k_nr) of the (C^∧N)₂Ir(LL′) complexes have been determined by using the lifetime and quantum efficiency. The k_r ranges between 2.0 × 10³ and 3.0 × 10⁵ s⁻¹ and k_nr spans a narrower range of values (5.0 × 10⁵ to 7.0 × 10⁶ s⁻¹).     

Synthesis and characterization of ruthenium(II) phenanthroline complexes containing quaternary amine substituents

A series of mixed-ligand complexes of ruthenium(II) containing 5-methylphenanthroline and trimethylamino-5-methylphenanthroline have been synthesized to investigate the impact of the quaternary amine on the photophysical properties. Thermal stability studies indicate that the quaternary amine is stable with respect to hydrolysis. Mass spectral analysis of the complexes revealed only fragments consistent with homolytic cleavage of the amines and no parent ions were observed. Both electrochemical and photophysical investigations indicate that the quaternary amine has little or no impact on the properties of the complex when compared to complexes lacking the amine.     

Synthesis, characterisation and theoretical studies on some piano-stool ruthenium and rhodium complexes containing substituted phenyl imidazole ligands

Reactions of the chloro-bridged arene ruthenium complexes [{(η⁶-arene)RuCl(μ-Cl}₂] (η⁶-arene = benzene, p-cymene) and structurally analogous rhodium complex [{(η⁵-C₅Me₅)RhCl(μ-Cl}₂] with imidazole based ligands viz., 1-(4-nitro-phenyl)-imidazole (NOPI), 1-(4-formylphenyl)-imidazole (FPI) and 1-(4-hydroxyphenyl)-imidazole (HPI) have been investigated. The resulting complexes have been characterised by elemental analyses, IR, ¹H and ¹³C NMR, electronic absorption and emission spectral studies. Crystal structure of the representative complex [(η⁵-C₅Me₅)RhCl₂(NOPI)] has been determined crystallographically. Geometrical optimisation on the complexes have been performed using exchange correlation functional B3LYP. Optimised bond lengths and angles of the complexes have been found to be in good agreement with our earlier reports and single crystal X-ray data of the complex [(η⁵-C₅Me₅)RhCl₂(NOPI)].     

Synthesis,characterization, and cytotoxic and antimicrobial activities of ruthenium(II) arene complexes with N,N-bidentate ligands

Three new complexes, [(η⁶-C₆H₆)RuCl(C₅H₄N-2-CH=N-Ar)]PF₆ (Ar = phenylmethylene (1), (4-methoxyphenyl)methylene (2), and phenylhydrazone (3)), were prepared by reacting [(η⁶-C₆H₆)Ru(μ-Cl)Cl]₂ with N,N′-bidentate ligands in a 1 : 2 ratio. Full characterization of the complexes was accomplished using ¹H and ¹³C NMR, elemental and thermal analyses, UV–vis and IR spectroscopy and single crystal X-ray structures. Single crystal structures confirmed a pseudo-octahedral three-legged, piano-stool geometry around Ru(II), with the ligand coordinated to the ruthenium(II) through two N atoms. The cytotoxicity of the mononuclear complexes was established against three human cancer cell lines and selectivity was also tested against non-cancerous human epithelial kidney (HEK 293) cells. The compounds were selective toward the tumor cells in contrast to the known anti-cancer drug 5-fluoro uracil which was not selective between the tumor cells and non-tumor cells. All the compounds showed moderate activity against MCF7 (human breast adenocarcinoma), but showed low antiproliferative activity against Caco-2 and HepG2. Also, antimicrobial activities of the complexes were tested against a panel of antimicrobial-susceptible and -resistant Gram-negative and Gram-positive bacteria. Of special interest is the anti-mycobacterial activity of all three synthesized complexes against Mycobacterium smegmatis, and bactericidal activity against resistant Enterococcus faecalis and methicillin-resistant Staphylococcus aureus ATCC 43300.     

Organometallic ruthenium, rhodium and iridium complexes containing a P-bound thiophene-2-(N-diphenylphosphino)methylamine ligand: Synthesis, molecular structure and catalytic activity

Reaction of Ph₂PNHCH₂-C₄H₃S with [Ru(η⁶-p-cymene)(μ-Cl)Cl]₂, [Ru(η⁶-benzene)(μ-Cl)Cl]₂, [Rh(μ-Cl)(cod)]₂ and [Ir(η⁵-C₅Me₅)(μ-Cl)Cl]₂ yields complexes [Ru(Ph₂PNHCH₂-C₄H₃S)(η⁶-p-cymene)Cl₂], 1, [Ru(Ph₂PNHCH₂-C₄H₃S)(η⁶-benzene)Cl₂], 2, [Rh(Ph₂PNHCH₂-C₄H₃S)(cod)Cl], 3 and [Ir(Ph₂PNHCH₂-C₄H₃S)(η⁵-C₅Me₅)Cl₂], 4, respectively. All complexes were isolated from the reaction solution and fully characterized by analytical and spectroscopic methods. The structure of [Ru(Ph₂PNHCH₂-C₄H₃S)(η⁶-benzene)Cl₂], 2 was also determined by single crystal X-ray diffraction. 1-4 are suitable precursors forming highly active catalyst in the transfer hydrogenation of a variety of simple ketones. Notably, the catalysts obtained by using the ruthenium complexes [Ru(Ph₂PNHCH₂-C₄H₃S)(η⁶-p-cymene)Cl₂], 1 and [Ru(Ph₂PNHCH₂-C₄H₃S)(η⁶-benzene)Cl₂], 2 are much more active in the transfer hydrogenation converting the carbonyls to the corresponding alcohols in 98-99% yields (TOF ≤ 200 h⁻¹) in comparison to analogous rhodium and iridium complexes.     

Synthesis, characterization, and SAMs electroactivity of ruthenium complexes with sulfur containing ligands

The vibrational and ¹H NMR data hints that the coordination of the 2,2′-dithiodipyridine (2-pySS) ligand to the [Ru(CN)₅]³⁻ metal center occurs through the sulfur atom instead of the nitrogen atoms which is usually observed for N-heterocyclic ligands. Electrochemical results show that this coordination mode implies an additional thermodynamic stabilization of the Ru^II over Ru^III oxidation state due to a relative stronger π-back-bonding interaction with the empty low-lying dπ orbitals of the sulfur atom. Computational data reinforce the experimental results showing that the 2-pySS Lewis base centers are located on the sulfur atoms. Ligands containing only sulfur atoms as coordination sites (2,2′-dithiodipyridine N-oxide (2-pySSNO), 1,4-dithiane (1,4-dt), and 2,6-dithiaspiro[3.3]heptane (asp)) were also coordinated to the [Ru(CN)₅]³⁻ metal center to undoubtedly correlate the electrochemical results with the ligand coordination atom. Among the synthesized compounds, the [Ru(CN)₅(1,4-dt)]³⁻ and [Ru(CN)₅(asp)]³⁻ complexes showed to be able to form self-assembled monolayers (SAMs) on gold. These SAMs, which were characterized by SERS (surface-enhanced Raman scattering) spectroscopy, successfully assessed the heterogeneous electron transfer reaction of the cytochrome c metalloprotein in physiological medium.     

Synthesis,characterization, electrochemistry,catalytic, and antimicrobial studies of ruthenium(III) complexes containing ONO donor ligands

A series of ruthenium(III) complexes [RuX(EPh₃)₂L] (where X = Cl or Br; E = P or As; L = deprotonated dibasic tridentate ligand) were prepared by the reaction of [RuX₃(EPh₃)₃] with Schiff bases (H₂L¹–H₂L⁴). The ligands were prepared by the condensation of N-4 phenyl/methyl semicarbazide with o-vanillin/o-hydroxy acetophenone. The complexes were characterized by elemental, physico-chemical, and electrochemical methods. Catalytic studies of these complexes for the oxidation of alcohols and aryl–aryl coupling were carried out. Antimicrobial experiments were also carried out.     

Synthesis and structural characterization of ruthenium(II) complexes bearing phosphine-pyrazolyl based tripod ligands

Phosphine-pyrazolyl based tripod ligands ROCH₂C(CH₂Pz)₂(CH₂PPh₂) (R = H, Me, allyl; Pz = pyrazol-1-yl) were efficiently synthesized and characterized. Reactions of these ligands with [Ru(η⁶-p-cymene)Cl₂]₂ afforded complexes of the type [Ru(η⁶-p-cymene)Cl₂](L) (6-8) in which the ligands exhibit κ¹-P-coordination to the metal center. Complex [Ru(η⁶-p-cymene)Cl₂{Ph₂PCH₂C(CH₂OH)(CH₂Pz)₂}] (6) underwent chloride-dissociation in CH₂Cl₂/MeCN to give complex [RuCl(η⁶-p-cymene){κ²(P,N)-Ph₂PCH₂C(CH₂OH)(CH₂Pz)₂}][Cl] (9). Complexes 6-9 demonstrated poor to moderate catalytic activity in the transfer hydrogenation of acetophenone. All these complexes were fully characterized by analytical and spectroscopic methods and their molecular structures were determined by X-ray crystallographic study.     

The preparation and structural characterization of ruthenium carbonyl cluster complexes containing 3,3 dimethylthietane ligands

The reaction of Ru₃(CO)₁₂ with 3,3 dimethylthietane (DMT) at 68°C yielded the new tetraruthenium cluster complex Ru₄(CO)₁₂(-SCH₂CMe₂CH₂)₂,1 in 23% yield. Compound1 was characterized crystallographically and was shown to consist of a puckered square of four ruthenium atoms with two DMT ligands bridging opposite sides of the cluster via the sulfur atoms. Compound1 reacts with CO (98°C/1 atm) to yield the new tetraruthenium complex Ru₄(CO)₁₃ (-SCH₂CMe₂CH₂),2 in 69% yield. Compound2 consists of a butterfly tetrahedral cluster of four ruthenium atoms with a DMT ligand bridging the wing-tip metal atoms. Addition of DMT to2 regenerates1 in 67% yield. Crystal data—1: space group = ,a=17.490(2) Å,b=18.899(3) Å,c=9.781(1) Å, =93.06(1)°, =91.06(1)°, =105.239(9)°,Z=4, 5799 reflections,R=0.026; for2: space group = P2₁/n,a=15.430(3) Å,b=18.285(4) Å,c=9.850(2) Å, =90.05(2)°,Z=4, 2111 reflections,R=0.036.     

Preparation, characterization and structure of ruthenium phosphine complexes containing non-innocent ligands

Phosphine ruthenate complexes containing the non-innocent ligands 4-chloro-1,2-phenylenediamine (opda-Cl) and 3,3′,4,4′-tetraamminebiphenyl (diopda) were synthesized and characterized by means of X-ray diffraction, electrochemistry, ³¹P{¹H} NMR and electronic spectroscopies. Crystals of cis-[RuCl₂(dppb)(bqdi-Cl)] complex were isolated as a mixture of two conformational isomers due to different positions of the chlorine atoms of the o-phenylene ligand in relation to the P1 atom of the phosphine moiety.     

Syntheses,characterization, and structures of three ruthenium complexes containing two monodentate dppm ligands

Three cis-Ru(dppm)₂XY complexes (XY?=?C₂O₄, 1; X?=?Cl, Y?=?N₃, 2; X?=?Y?=?N₃, 3) were prepared by reactions of cis-Ru(dppm)₂Cl₂ with (NH₄)₂C₂O₄, a mixture of NaN₃ and NaPF₆, and only NaN₃, respectively, while 3 could also be obtained from further reaction of 2 with NaN₃ undergoing a facile chloride abstraction. All complexes have been characterized by IR, NMR, UV–vis, and luminescence spectroscopic analyses as well as X-ray diffraction studies. Of these structures, 1 shows oxalate coordinates to Ru as a chelating ligand, while 2 displays Ru and azide linear, and 3 gives two azide groups cis to each other, which are different from two substituting ligands commonly lying in trans positions in Ru(P–P)₂ complexes by using cis-Ru(dppm)₂Cl₂ as a precursor.     

Synthesis,characterization, crystal structure,and DNA-binding of ruthenium(II) complexes of heterocyclic nitrogen ligands resulting from a benzimidazole-based quinazoline derivative

The reaction of cis-[RuCl₂(dmso)₄] with [6-(2-pyridinyl)-5,6-dihydrobenzimidazo[1,2-c]quinazoline] (L) afforded in pure form a blue ruthenium(II) complex, [Ru(L¹)₂] (1), where the original L changed to [2-(1H-benzoimidazol-2-yl)-phenyl]-pyridin-2-ylmethylene-amine (HL¹ ). Treatment of RuCl₃?·?3H₂O with L in dry tetrahydrofuran in inert atmosphere led to a green ruthenium(II) complex, trans-[RuCl₂(L²)₂] (2), where L was oxidized in situ to the neutral species 6-pyridin-yl-benzo[4,5]imidazo[1,2-c]quinazoline (L² ). Complex 2 was also obtained from the reaction of RuCl₃?·?3H₂O with L² in dry ethanol. Complexes 1 and 2 have been characterized by physico-chemical and spectroscopic tools, and 1 has been structurally characterized by single-crystal X-ray crystallography. The electrochemical behavior of the complexes shows the Ru(III)/Ru(II) couple at different potentials with quasi-reversible voltammograms. The interaction of these complexes with calf thymus DNA by using absorption and emission spectral studies allowed determination of the binding constant K _b and the linear Stern–Volmer quenching constant K _SV.     

Synthesis,spectroscopic characterization and antibacterial sensitivity of some chloro dimethylsulfoxide/tetramethylenesulfoxide ruthenium(II) and ruthenium(III) complexes with 2-aminobenzothiazole

Synthesis and characterization of seven ruthenium(II) and ruthenium(III) complexes of sulfoxide with 2-aminobenzothiazole are reported. Three different formulations exist: [cis,cis,cis-RuCl₂(SO)₂(2-abtz)₂] and [trans,trans,trans-RuCl₂(SO)₂(2-abtz)₂] and [trans-RuCl₄(SO)(2-abtz)] ^? [X]⁺ (where SO?=?dimethyl sulfoxide (dmso) or tetramethylenesulfoxide (tmso); 2-abtz?=?2-aminobenzothiazole and [X]⁺?=?[H(abtz)]⁺, [Na⁺]. These complexes were characterized by elemental analyses, conductivity measurements, magnetic susceptibility, FTIR, ¹H NMR, ¹³C{¹H} NMR and electronic spectroscopy. Some of the complexes were screened for their antibacterial activity and are found to be potent against the gram negative bacteria Escherichia coli.     

Synthesis, characterization, and X-ray structural analysis of some half-sandwich ruthenium(II) arene complexes with new N,S-donor Schiff base ligands

A series of cationic, half-sandwich ruthenium complexes with the general formula [(η⁶-arene)RuCl(R¹S-C₆H₄-2-CHNR²)]⁺ (arene = p-cymene or hexamethylbenzene; R¹ = CH₂Ph, ⁱPr, or Et; R² = aryl) have been prepared from the reaction of [(η⁶-arene)RuCl₂]₂ with various N,S-donor Schiff base ligands derived from 2-(alkylthio)benzaldehyde and several primary amines. All of the ruthenium complexes were characterized by IR, ¹H NMR, electrochemistry, and UV/Vis spectroscopies. The p-cymene complexes undergo irreversible oxidations while the hexamethylbenzene complexes undergo quasi-reversible oxidations. The molecular structures of ligand 1a and complexes 4a, 4l, and 5e were determined by X-ray crystallography.