The reactivity of nitrosyl ruthenium complexes containing polypyridyl ligands

A series of cis nitrosyl complexes containing polypyridyl ligands were prepared and characterized as cis-[RuL(bpy)₂(NO)](PF₆)₃ (L = pyridine, 4-picoline, or 4-acetylpyridine), by elemental analysis, u.v.–vis. and i.r. spectroscopy, and by electrochemical techniques such as cyclic voltammetry, differential pulse voltammetry, spectroelectrochemistry, and coulometry. The complexes exhibit stretching frequencies (NO) at ca. 1950 cm^–1 indicating that nitrosyl group has a sufficiently high degree of nitrosonium ion (NO⁺) character. In non-aqueous solution, the reduction of these complexes induce nitrosyl to nitro conversion. In aqueous solution the reduction product is cis-[RuL(bpy)₂(NH₃)]²⁺ formed by a six electron mechanism. The nitrosyl compounds are susceptible to nucleophilic attack by hydroxide ion. The equilibrium constants were determined.     

Cyclometalated ruthenium chloro and nitrosyl complexes

The novel cyclometalated Ru(III) complex, [Ru(eta(2)-phpy)(trpy)Cl][PF(6)].toluene 1, and the [Ru-NO](6) complex, [Ru(eta(2)-phpy)(trpy)NO][PF(6)](2) 2, where trpy is 2,2': 6',2'-terpyridine and phpy is 2-phenylpyridine, have been prepared and characterized by elemental analysis, IR, (1)H NMR, and electronic absorption spectroscopies, cyclic voltammetry, and crystallography. The crystal structure of 1 showed the chloride ion trans to the sigma-bonding phenyl group of phpy and is an unusual example of a stable paramagnetic cyclometalated complex. The crystal structure of 2 shows the nitrosyl ligand trans to the sigma-bonding phenyl group of phpy. The significant distortion of the normally linear Ru-NO bond angle (167.1(4) degrees) can be largely ascribed to the strong sigma-donor properties of the phenyl group.     

Quantum chemical study of the bond orders in the ruthenium,diruthenium and dirhodium nitrosyl complexes

Density functional calculations with the B3LYP functional were carried out for the [Ru(NO)Cl₅]²⁻, [Ru(NO)(NH₃)₅]³⁺, [Ru(NO)(CN)₅]²⁻, [Ru(NO)(CN)₅]³⁻, [Ru(NO)(hedta)]^q (hedta = N-(hydroxyethyl)ethylenediaminetriacetate triple-charged anion; q = 0, −1, −2), Rh₂(O₂CR)₄, Rh₂(O₂CR)₄(NO)₂, Ru₂(O₂CR)₄, Ru₂(O₂CR)₄(NO)₂, Ru₂(dpf)₄, and Ru₂(dpf)₄(NO)₂ (dpf = N,N′-diphenylformamidinate ion; R = H, CH₃, CF₃) complexes. The electronic structure was analyzed in terms of Mayer and Wiberg bond order indices. The technique of bond order indices decomposition into σ-, π-, and δ-contributions was proposed.     

Spectral,thermal and biological activity studies on ruthenium(II) complexes with some pyridylamines

Complexes resulted from the interaction of [Ph₃P]₃RuCl₂ with 2-aminoethylpyridine (aepy), 2-hydrazinopyridine (hzpy) and dipicolylamine (dpa) with KPF₆ have been isolated from ethanol. The structures of the complexes were investigated using elemental analyses, IR, magnetic moment, UV-Vis and ¹H NMR spectroscopy. The complexes have been isolated as [Ru(hzpy)₃](PF₆)₂, [Ru(hzpy)₂(aepy)](PF₆)₂, [Ru(hzpy)(aepy)₂](PF₆)₂, [Ru(dpa)₂](PF₆)₂ in an octahedral geometry. The thermal decomposition of complexes was discussed in terms of their structures and the thermodynamic parameters were evaluated. The metal complexes were screened for their antibacterial activity against bacterial species, Escherichia coli, Staphylococcus aureus, as well as fungus (Candida). The activity data show the metal complexes have potent antibacterials against one ore more bacterial species.     

Photochemical nitric oxide precursors: synthesis,photochemistry, and ligand substitution kinetics of ruthenium salen nitrosyl and ruthenium salophen nitrosyl complexes

Described are syntheses, characterizations, and photochemical reactions of the nitrosyl complexes Ru(salen)(ONO)(NO) (I, salen = N,N'-ethylenebis(salicylideneiminato) dianion), Ru(salen)(Cl)(NO) (II), Ru((t)Bu(4)salen)(Cl)(NO) (III,(t)Bu(4)salen = N,N'-ethylenebis(3,5-di-tert-butylsalicylideneiminato) dianion), Ru((t)Bu(4)salen)(ONO)(NO) (IV), Ru((t)Bu(2)salophen)(Cl)(NO) (V, (t)Bu(2)salophen = N,N'-1,2-phenylenediaminebis(3-tert-butylsalicylideneiminato) dianion), and Ru((t)Bu(4)salophen)(Cl)(NO) (VI, (t)Bu(4)salophen = N,N'-1,2-phenylenebis(3,5-di-tert-butylsalicylideneiminato) dianion). Upon photolysis, these Ru(L)(X)(NO) compounds undergo NO dissociation to give the ruthenium(III) solvento products Ru(L)(X)(Sol). Quantum yields for 365 nm irradiation in acetonitrile solution fall in a fairly narrow range (0.055-0.13) but decreased at longer lambda(irr). The quantum yield (lambda(irr) = 365 nm) for NO release from the water soluble complex [Ru(salen)(H(2)O)(NO)]Cl (VII) was 0.005 in water. Kinetics of thermal back-reactions to re-form the nitrosyl complexes demonstrated strong solvent dependence with second-order rate constants k(NO) varying from 5 x 10(-4) M(-1) s(-1) for the re-formation of II in acetonitrile to 5 x 10(8) M(-1) s(-1) for re-formation of III in cyclohexane. Pressure and temperature effects on the back-reaction rates were also examined. These results are relevant to possible applications of photochemistry for nitric oxide delivery to biological targets, to the mechanisms by which NO reacts with metal centers to form metal-nitrosyl bonds, and to the role of photochemistry in activating similar compounds as catalysts for several organic transformations. Also described are the X-ray crystal structures of I and V.     

The synthesis and reactivity of some indenyl and bis-indenyl ruthenium carbonyl complexes

The reaction of [Ru₃(CO)₁₂] (1), with indene in refluxing xylene affords [{(η⁵-C₉H₇)Ru(CO)₂}₂] (2), in high yield. An analogous reaction of 1 with 2-phenylindene affords the expected dinuclear complex [{(η⁵-C₉H₆Ph)Ru(CO)₂}₂] (5), and a heptaruthenium cluster [(C₉H₄Ph)Ru₇(μ-H)(μ-CO)₂(CO)₁₆] (6). The indenyl ligand in compound 6 exhibits a novel bonding mode in which the benzenoid ring is μ₄,η¹:η¹:η²:η² bound to the cluster. Refluxing 1 with bis-indenyl methane affords the dinuclear complex [Ru₂(CO)₄{μ-(η⁵-C₉H₆)₂CH₂}] (7), which reacts with iodine via Ru-Ru bond cleavage to give [Ru₂I₂(CO)₄{(η⁵-C₉H₆)₂CH₂}] (8).     

Electronic structure and spectra of binuclear bridged nitrosyl ruthenium complexes

The B3LYP method in the LanL2DZ basis set was used to carry out geometry optimization for the binuclear bridged complexes [RuCl₄(NO)(μ-Pyz)Ru(P)(CO)]^?, [Ru(Bipy)₂(NO)(μ-Pyz)Ru(NH₃)₅]⁵⁺, and [(NC)Ru(Py)₄(μ-CN)Ru(Py)₄NO]³⁺ (Pyz is pyrazine). The electronic spectra of the complexes were calculated by the TDDFT and CINDO-CI methods with allowance for solvation effects. The ground-state electronic configurations of the two ruthenium atoms in these compounds were shown to be different. Among the lower excited states of all complexes, states with essentially weakened Ru-NO bonds were found. The strong absorption in the visible region of the spectrum of [Ru(Py)₄NO-CN-Ru(Py)₄CN]³⁺ is due to the interfragment electron transfer Ru^II → {RuNO} accompanied by weakening of the bond between nitrogen oxide and the complex.     

Preparation, characterization, and catalytic properties of ruthenium nitrosyl complexes with polypyrazolylmethane ligands

Ruthenium(II) nitrosyl complexes with polypyrazolylmethanes, [(Bpm)Ru(NO)Cl₃] [Bpm = bis(1-pyrazolyl)methane, 1], [(Bpm^∗)Ru(NO)Cl₃] [Bpm^∗ = bis(3,5-dimethyl-1-pyrazolyl)methane, 2], [(Tpm)Ru(NO)Cl₂][PF₆] [Tpm = tris(1-pyrazolyl)methane, 3], and [(Tpm^∗)Ru(NO)Cl₂][PF₆] [Tpm^∗ = tris(3,5-dimethyl-1-pyrazolyl)methane, 4], have been synthesized and characterized. The solid-state structures of [(Bpm^∗)Ru(NO)Cl₃] (2) and [(Tpm^∗)Ru(NO)Cl₂][PF₆] (4) were determined by single-crystal X-ray crystallographic analyses. These complexes have been tested as catalysts in the transfer hydrogenation of several ketones under mild conditions.     

XRD and EXAFS study of nitrato ammine complexes of nitrosyl ruthenium

The structure of trans-[RuNO(NH₃)₄(H₂O)](NO₃)₃ (I) and trans-[RuNO(NH₃)₄(NO₃)](NO₃)₂ (II) was determined by XRD. Crystallographic data are as follows: space group I4₁/a; a = b = 18.280(1) Å, c = 15.129(1) Å, R = 0.0244 (I), and space group Cm, a = 11.5620(3) Å, b = 7.9934(2) Å, c = 7.7864(2) Å, β = 127.124(1)°, R = 0.0139 (II). Interatomic distances for complex particles of fac- and mer- [RuNO(NH₃)₂(NO₃)₃] (III and IV, respectively) were determined by EXAFS.     

Synthesis,characterization, and biological activity of some lanthanide ternary complexes

Five complexes have been synthesized by the reaction of lanthanide(III) nitrate with 2-thenoyltrifluoroacetone (HTTA) and p-hydroxybenzoic acid (L). The complexes have been characterized by elemental analysis, molar conductivity, FT-IR, UV-Vis, ¹H NMR, TG-DTA, XPS, and transmission electron microscope. The general formula of the complexes is Na[Ln(TTA)₃L] (Ln?=?La³⁺,?Ce³⁺,?Nd³⁺,?Eu³⁺,?Er³⁺). The antibacterial activities indicate that all five complexes exhibit antibacterial ability against Escherichia coli and Staphylococcus aureus with broad antimicrobial spectrums. The antitumor activity of the five complexes against K562 tumor cell in vitro is measured using methyl thiazolyl tetrazolium (MTT) colorimetry. The results show that the complexes induce K562 tumor cell apoptosis, and the complexes exhibit inhibitory effect on leukemia K562 cells.     

Ozone,chemical reactivity and biological functions

Various aspects of the structure, the reactivity in organic synthesis, in the atmosphere, in environment, in biology of ozone are described. Emphasis is placed on the relation with singlet oxygen and dihydrotrioxide.     

Spectroscopy and photochemical reactivity of cyclooctadiene platinum complexes

The spectroscopic and photochemical properties of a series of 1,5-cyclooctadiene platinum complexes of the type [(COD)Pt(R)₂] (R=alkyl, alkynyl, or aryl) were examined. The observed photoreactivity is wavelength dependent and observed reaction rates correlate with the donor-strength of the R group. For strongly donating substituents like adamantylmethyl, benzyl or iso-propyl rates were increased by factors of about 100 for a given model reaction compared to the dimethyl derivative. The products were determined by NMR spectroscopy. Different reaction pathways were found depending on the substituents R. Theoretical calculations (DFT) on the electronic structure revealed the character of optical transitions and excited states.     

Transition metal nitrosyl compounds,Part XXV1 Studies of some nitrosyl complexes of molybdenum and tungsten

Summary On u.v. irradiation, the dinitrosyldithiocarbamato M(NO)₂ (S2 CNR2 )2 (M = Mo or W) complexes are converted quantitatively into the mononitrosyl M(NO)(S₂CNR₂)₃ complexes. The tungsten complex exhibits nonrigid behaviour at high temperatures; the activation energy for this process has been determined and compared to that of the molybdenum analogue. The M(NO)₂ (MeCOCHCOMe)₂ and M(NO)₂ [(O)SCNR₂]₂ compounds have been prepared; these undergo conversion into uncharacterized nitrosyl derivatives upon irradiation. Cationic complexes of the type [M(NO)₂ (MeCN)₄]2+, [M(NO)₂ (MeCN)₃ X]+ and [M(NO)₂ (MeCN)₂ (MeCOCHCOMe)]+ have been prepared and their exchange with CD₃CN studied. Exchange occursvia a dissociative process and is stereospecific for [M(NO)₂ (MeCN)₄ ]2+ (M = Mo or W) and [M(NO)₂ (MeCN)₃ X]+ (M = MO, X = Cl; M = W, X = Br).     

Synthesis, spectroscopic characterization, photochemical and photophysical properties and biological activities of ruthenium complexes with mono- and bi-dentate histamine ligand

The monodentate cis-[Ru(phen)(2)(hist)(2)](2+)1R and the bidentate cis-[Ru(phen)(2)(hist)](2+)2A complexes were prepared and characterized using spectroscopic ((1)H, ((1)H-(1)H)COSY and ((1)H-(13)C)HSQC NMR, UV-vis, luminescence) techniques. The complexes presented absorption and emission in the visible region, as well as a tri-exponential emission decay. The complexes are soluble in aqueous and non-aqueous solution with solubility in a buffer solution of pH 7.4 of 1.14 × 10(-3) mol L(-1) for (1R + 2A) and 6.43 × 10(-4) mol L(-1) for 2A and lipophilicity measured in an aqueous-octanol solution of -1.14 and -0.96, respectively. Photolysis in the visible region in CH(3)CN converted the starting complexes into cis-[Ru(phen)(2)(CH(3)CN)(2)](2+). Histamine photorelease was also observed in pure water and in the presence of BSA (1.0 × 10(-6) mol L(-1)). The bidentate coordination of the histamine to the ruthenium center in relation to the monodentate coordination increased the photosubstitution quantum yield by a factor of 3. Pharmacological studies showed that the complexes present a moderate inhibition of AChE with an IC(50) of 21 μmol L(-1) (referred to risvagtini, IC(50) 181 μmol L(-1) and galantamine IC(50) 0.006 μmol L(-1)) with no appreciable cytotoxicity toward to the HeLa cells (50% cell viability at 925 μmol L(-1)). Cell uptake of the complexes into HeLa cells was detected by fluorescence confocal microscopy. Overall, the observation of a luminescent complex that penetrates the cell wall and has low cytotoxicity, but is reactive photochemically, releasing histamine when irradiated with visible light, are interesting features for application of these complexes as phototherapeutic agents.     

Immobilized ruthenium complexes and aspects of their reactivity

Methodologies for the immobilization and characterization of ruthenium complexes into/onto functionalized silica gel, zeolites, polymers, dendrimers, sol–gel, nano and microparticles are described. The corresponding spectroscopic, electrochemical, and photochemical properties as well as chemical reactivities are used for their characterization and study. Comparison between the reactivities of immobilized and in solution species is presented. Some biological applications are also described.     

Rhodium and ruthenium tetracarboxylate nitrosyl complexes: Electronic structure and metal-metal bond

The electronic structure of the tetracarboxylates M₂(μ-O₂CH)₄, M₂(μ-O₂CH)₄(L)₂ (M = Ru, Rh; L = H₂O, NO) was analyzed by the density functional theory with full geometry optimization. The inclusion of nitrogen oxide orbitals into the molecular orbitals forming the metal-metal bond affects all of the main characteristics of this bond and the concomitant properties. In the case of rhodium tetracarboxylates, one can consider destruction of the Rh-Rh covalent σ-bond and reorientation of two electrons from the internal region of the Rh₂(μ-O₂CH)₄ core to the outside, toward the axial ligands to give Rh-N covalent bonds. The axial coordination of nitrogen oxide in Ru₂(μ-O₂CR)₄ is accompanied by destruction of the metal-metal π-bond.     

Synthesis of trithiolanes and tetrathianes from thiiranes catalyzed by ruthenium salen nitrosyl complexes

The compound [Ru(salen)(NO)(H(2)O)](SbF(6)) (1) (salen = N,N'-ethylene-bis-salicylidene aminate) reacts catalytically with thiiranes and converts them to olefins and 1,2,3,4-tetrathianes or 1,2,3-trithiolanes. The monosubstituted thiiranes styrene sulfide and propylene sulfide reacted to form the corresponding olefin and the 4-substituted 1,2,3-trithiolane in a 2:1 ratio in isolated yields in excess of 90%. The disubstituted thiirane cis-stilbene sulfide was converted to cis-stilbene and 5,6-trans-1,2,3,4-diphenyltetrathiane in a 3:1 ratio in the presence of a catalytic amount of 1 in CD(3)NO(2). Coordination of cis-stilbene sulfide to the salen complex in a ligand substitution reaction was established by isolation of [Ru(salen)(NO)(cis-stilbene sulfide)](SbF(6)) (6). (1)H NMR studies performed on 6 indicated that the salen macrocycle had rearranged upon thiirane coordination. A similar rearrangement was found to be stabilized by other ligands including tetramethylethylene sulfide, tetrahydrothiophene, and d(3)-acetonitrile. The alpha-deuterio-cis-stilbene sulfide catalyst adduct (d-6) reacted with unlabeled cis-stilbene sulfide to form deuterium-labeled trans-diphenyl-tetrathiane and unlabeled cis-stilbene as shown by GCMS and (1)H NMR. Thus, the solution thiirane behaves as a sulfur donor and forms olefin, whereas the coordinated thiirane becomes the cyclic polysulfide. beta-cis-Deuteriostyrene sulfide was used to show that ring closure to form cyclic polysulfide incorporated inversion of stereochemistry versus starting thiirane. A mechanism for catalysis consistent with experimental data is presented that requires coordination of thiirane to the metal complex followed by bimolecular attack of free thiirane on the coordinated thiirane.