A robust NNP-type ruthenium (II) complex for alcohols dehydrogenation to esters and pyrroles

A Ru (II) complex bearing pyridyl-based benzimidazole-phosphine tridentate NNP ligand was synthesized and structurally characterized by NMR, IR. The complex can efficiently and selectively catalyze the acceptorless dehydrogenation of primary alcohols to esters under relatively mild conditions and the synthesis of pyrroles by means of the reactions of secondary alcohols and β-amino alcohols through acceptorless deoxygenation condensation.     

The catalytic activity of a cyclometalated ruthenium(III) complex for aerobic oxidative dehydrogenation of benzylamines

The ruthenium(III) complex bearing benzo[h]quinoline as a cyclometalated ligand was synthesized and characterized by ESI-MS, elemental analysis, cyclic voltammetry and crystallography. The complex serves as an efficient catalyst for the aerobic oxidative dehydrogenation of benzylamines to the corresponding benzonitriles under mild conditions.     

Half-sandwich arene ruthenium(II)-enzyme complex

The 1.6 [Angstrom] X-ray crystal structure of [(eta(6)-p-cymene)Ru(lysozyme)Cl(2)], the first of a half-sandwich complex of a protein, shows selective ruthenation of Nepsilon of the imidazole ring of His15.     

Reactivity and improved synthesis of aquotris(dimethylsulfoxide)bis-(trifluoroacetato)ruthenium(II)

Reaction of [Ru(Me₂SO)₃(O₂CCF₃)₂(H₂O)] with triphenylphosphine and triphenylarsine gives complexes of the type [Ru(Me₂SO)(O₂CCF₃)₂(EPh₃)₂] (where E?=?P or As) in which there is a partial substitution of dimethylsulfoxide. Reaction with unidentate N donors resulted in [Ru(O₂CCF₃)₂L₄] (where L?=?pyridine, imidazole, benzimidazole); reaction with diimines yielded [Ru(L–L)₃](O₂CCF₃)₂ (where L–L?=?2,2′-bipyridyl, 1,10-phenanthroline). All complexes have been characterized by elemental analysis, conductivity measurements, IR and ¹H NMR spectroscopy.     

Oxygenation of a ruthenium(II) thiolate to a ruthenium(II) sulfinate proceeds via ruthenium(III)

Exposure of acetonitrile/methanol solutions of [PPN][Ru(DPPBT)3] [PPN = bis(triphenylphosphoranylidene); DPPBT = 2-diphenylphosphinobenzene thiolate] to oxygen initiates metal-centered oxidation, yielding the ruthenium(III) thiolate Ru(DPPBT)3. Ru(DPPBT)3 further reacts with oxygen, at sulfur, to give the ruthenium(III) sulfinate complex [Ru(DPPBT-O2)2(DPPBT)], which is reduced under ambient conditions to [PPN][Ru(DPPBT-O2)2(DPPBT)]. Ruthenium(II) sulfinate is the only product isolated from acetonitrile/methanol. Yellow crystals of [PPN][Ru(DPPBT-O2)2(DPPBT)] were obtained. Ruthenium(III) sulfinate was isolated as green prism-shaped crystals upon oxygenation of [PPN][Ru(DPPBT)3] in chlorobenzene/hexane. Electrochemical oxidation of ruthenium(II) sulfinate yields the ruthenium(III) derivative, which is rapidly reduced back to ruthenium(II) upon the addition of hydroxide.     

Synthesis, catalytic activity and phytotoxicity of a supported nickel(II) Schiff base complex

A supported Ni(II) complex has been synthesized and characterized by FTIR, UV–vis diffuse reflectance spectroscopy, thermogravimetric analysis and scanning electron microscopy. Its catalytic activity was evaluated for alkyne–azide coupling and benzothiazole synthesis. These reactions were found to require mild conditions, reaction times, and most importantly, could be carried out in aqueous medium. The catalyst could be easily recovered and reused five times without significant decrease in its activity. Leaching tests indicated that the catalyst is truly heterogeneous. The nickel complex was tested for its inhibition of germination of MTU 7029 seeds. Rice (MTU 7029, Oryza sativa) is a staple crop in southeast Asia.     

Hydrolytic cleavage of DNA by a ruthenium(II) polypyridyl complex

The complex [Ru(bpy)2(BPG)]Cl2 (1) containing hydrogen-bond donor (N-H atoms) and acceptor (O atoms) groups mediates hydrolytic cleavage of plasmid pBR322 DNA in an enzyme-like manner. The kinetic aspects of DNA cleavage under pseudo- and true-Michaelis-Menten conditions are detailed.     

Photocontrolled DNA binding of a receptor-targeted organometallic ruthenium(II) complex

A photoactivated ruthenium(II) arene complex has been conjugated to two receptor-binding peptides, a dicarba analogue of octreotide and the Arg-Gly-Asp (RGD) tripeptide. These peptides can act as "tumor-targeting devices" since their receptors are overexpressed on the membranes of tumor cells. Both ruthenium-peptide conjugates are stable in aqueous solution in the dark, but upon irradiation with visible light, the pyridyl-derivatized peptides were selectively photodissociated from the ruthenium complex, as inferred by UV-vis and NMR spectroscopy. Importantly, the reactive aqua species generated from the conjugates, [(η(6)-p-cym)Ru(bpm)(H(2)O)](2+), reacted with the model DNA nucleobase 9-ethylguanine as well as with guanines of two DNA sequences, (5')dCATGGCT and (5')dAGCCATG. Interestingly, when irradiation was performed in the presence of the oligonucleotides, a new ruthenium adduct involving both guanines was formed as a consequence of the photodriven loss of p-cymene from the two monofunctional adducts. The release of the arene ligand and the formation of a ruthenated product with a multidentate binding mode might have important implications for the biological activity of such photoactivated ruthenium(II) arene complexes. Finally, photoreactions with the peptide-oligonucleotide hybrid, Phac-His-Gly-Met-linker-p(5')dCATGGCT, also led to arene release and to guanine adducts, including a GG chelate. The lack of interaction with the peptide fragment confirms the preference of such organometallic ruthenium(II) complexes for guanine over other potential biological ligands, such as histidine or methionine amino acids.     

Facile fabrication of robust multilayer films: visible light-triggered chemical cross-linking by the catalysis of a ruthenium(II) complex

Highly stable covalently attached multilayer films were constructed by visible-light irradiation of hydrogen-bonding directed multilayer films of poly(allylamine) and poly(4-vinylphenol).     

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.     

Catecholase activity of a copper(II) complex with a macrocyclic ligand: unraveling catalytic mechanisms

We report the structure, properties and a mechanism for the catecholase activity of a tetranuclear carbonato-bridged copper(II) cluster with the macrocyclic ligand [22]pr4pz (9,22-dipropyl-1,4,9,14,17,22,27,28,29, 30-decaazapentacyclo[22.2.1.1(4,7).1(11,14). 1(17,20)]triacontane-5,7(28),11(29),12,18, 20(30),24(27),25-octaene). In this complex, two copper ions within a macrocyclic unit are bridged by a carbonate anion, which further connects two macrocyclic units together. Magnetic susceptibility studies have shown the existence of a ferromagnetic interaction between the two copper ions within one macrocyclic ring, and a weak antiferromagnetic interaction between the two neighboring copper ions of two different macrocyclic units. The tetranuclear complex was found to be the major compound present in solution at high concentration levels, but its dissociation into two dinuclear units occurs upon dilution. The dinuclear complex catalyzes the oxidation of 3,5-di-tert-butylcatechol to the respective quinone in methanol by two different pathways, one proceeding via the formation of semiquinone species with the subsequent production of dihydrogen peroxide as a byproduct, and another proceeding via the two-electron reduction of the dicopper(II) center by the substrate, with two molecules of quinone and one molecule of water generated per one catalytic cycle. The occurrence of the first pathway was, however, found to cease shortly after the beginning of the catalytic reaction. The influence of hydrogen peroxide and di-tert-butyl-o-benzoquinone on the catalytic mechanism has been investigated. The crystal structures of the free ligand and the reduced dicopper(I) complex, as well as the electrochemical properties of both the Cu(II) and the Cu(I) complexes are also reported.     

Formation of a dinuclear imido complex from the reaction of a ruthenium(VI) nitride with a ruthenium(II) hydride

The treatment of [Ru(L(OEt))(N)Cl(2)] (1; L(OEt)(-) = [Co(η(5)-C(5)H(5)){P(O)(OEt)(2)}(3)](-)) with Et(3)SiH affords [Ru(L(OEt))Cl(2)(NH(3))] (2), whereas that with [Ru(L(OEt))(H)(CO)(PPh(3))] (3) gives the dinuclear imido complex [(L(OEt))Cl(2)Ru(μ-NH)Ru(CO)(PPh(3))(L(OEt))] (4). The imido group in 4 binds to the two ruthenium atoms unsymmetrically with Ru-N distances of 1.818(6) and 1.952(6) ?. The reaction between 1 and 3 at 25 °C in a toluene solution is first order in both complexes with a second-order rate constant determined to be (7.2 ± 0.4) × 10(-5) M(-1) s(-1).     

Synthesis,characterization, spectroscopic study,and catalytic behavior of ruthenium(II) o-phenanthroline complex with dipicolinate

A new dipicolinate complex of Ru(II), cis-[Ru(phen)₂dipic]?·?9.5H₂O (1), where dipic is dipicolinate or pyridine-2,6-dicarboxylate and phen is 1,10-phenanthroline, has been synthesized and characterized by elemental analysis, spectroscopic (IR, UV-Vis), cyclic voltammetry, and single-crystal X-ray diffraction. ORTEP drawing of cis-[Ru(phen)₂dipic]?·?9.5H₂O shows that the coordination geometry around Ru(II) is a distorted octahedron. It crystallizes in the triclinic system, with space group P 1, a?=?10.4633(2)?Å, b?=?13.6332(4)?Å, c?=?13.6637(4)?Å, α?=?67.516(3)°, β?=?69.757(2)°, γ?=?77.201(2)°, V?=?1680.74(8)?ų, Z?=?2, and R _int?=?0.0311. In 1, two phen are bidentate N,N′ ligands. The Ru(II) in 1 is bonded to dipicolinate through pyridine nitrogen and one oxygen of carboxylate groups, thus pyridine-2,6-dicarboxylate is a bidentate N,O ligand. Efficient and selective oxidation of alcohols with NaIO₄ as oxidant was conducted by this complex catalyst in CH₃OH/H₂O as solvents under air at room temperature.     

Reactions of a ruthenium(II) arene antitumor complex with cysteine and methionine

The Ru(II) organometallic antitumor complex [(eta(6)-biphenyl)RuCl(en)][PF(6)] (1) reacts slowly with the amino acid L-cysteine (L-CysH(2)) in aqueous solution at 310 K. Reactions were followed over periods of up to 48 h using HPLC, electronic absorption spectroscopy, LC-ESI-MS, and 1D or 2D (1)H and (15)N NMR spectroscopy. Reactions at a 1 mM/2 mM (Ru/L-CysH(2)) ratio were multiphasic in acidic solutions (pH 5.1) and appeared to involve aquation as the first step. Initially, 1:1 adducts involving substitution of Cl by S-bound or O-bound L-CysH(2), [(eta(6)-biphenyl)Ru(S-L-CysH)(en)](+) (4a) and [(eta(6)-biphenyl)Ru(O-L-CysH(2))(en)](2+) (4b) formed, followed by the cystine adduct [(eta(6)-biphenyl)Ru(O-Cys(2)H(2))(en)](2+) (3), and two dinuclear complexes from which half or all of the chelated ethylenediamine had been displaced, [(eta(6)-biphenyl)Ru(H(2)O)(microS,N-L-Cys)Ru(eta(6)-biphenyl)(en)](2+) (5) containing one bridging cysteine, and [(eta(6)-biphenyl)Ru(O,N-L-Cys-S)(S-L-Cys-N)Ru(eta(6)-biphenyl)(H(2)O)] (6) containing two bridging cysteines. The unusual cluster species [(biphenyl)Ru](8) (7a) was also detected by MS and was more prevalent in reactions at higher L-CysH(2) concentrations. Complex 5 was the dominant product at pH 2-5, but overall, only ca. 50% of 1 reacted with L-CysH(2) in these conditions. The reaction between 1 and L-CysH(2) was suppressed in 50 mM triethylammonium acetate solution at pH > 5 or in 100 mM NaCl. Only 27% of complex 1 reacted with L-methionine (L-MetH) at an initial pH of 5.7 after 48 h at 310 K and gave rise to only one adduct [(eta(6)-biphenyl)Ru(S-L-MetH)(en)](2+) (8).     

Mechanistic insights into photochromic behavior of a ruthenium(II)-pterin complex

The pterin‐coordinated ruthenium complex, [Ru^II(dmdmp)(tpa)]⁺ ( 1 ) (Hdmdmp=N,N‐dimethyl‐6,7‐dimethylpterin, tpa=tris(2‐pyridylmethyl)amine), undergoes photochromic isomerization efficiently. The isomeric complex ( 2 ) was fully characterized to reveal an apparent 180° pseudorotation of the pterin ligand. Photoirradiation to the solution of 1 in acetone with incident light at 460 nm resulted in dissociation of one pyridylmethyl arm of the tpa ligand from the Ru^II center to give an intermediate complex, [Ru(dmdmp)(tpa)(acetone)]²⁺ ( I ), accompanied by structural change and the coordination of a solvent molecule to occupy the vacant site. The quantum yield (?) of this photoreaction was determined to be 0.87 %. The subsequent thermal process from intermediate I affords an isomeric complex 2 , as a result of the rotation of the dmdmp^2? ligand and the recoordination of the pyridyl group through structural change. The thermal process obeyed first‐order kinetics, and the rate constant at 298 K was determined to be 5.83×10^?5 s^?1. The activation parameters were determined to be ΔH^≠=81.8 kJ mol^?1 and ΔS^≠=?49.8 J mol^?1 K^?1. The negative ΔS^≠ value indicates that this reaction involves a seven‐coordinate complex in the transition state (i.e., an interchange associative mechanism). The most unique point of this reaction is that the recoordination of the photodissociated pyridylmethyl group occurs only from the direction to give isomer 2 , without going back to starting complex 1 , and thus the reaction proceeds with 100 % conversion efficiency. Upon heating a solution of 2 in acetonitrile, isomer 2 turned back into starting complex 1 . The backward reaction is highly dependent on the solvent: isomer 2 is quite stable and hard to return to 1 in acetone; however, 2 was converted to 1 smoothly by heating in acetonitrile. The activation parameters for the first‐order process in acetonitrile were determined to be ΔH^≠=59.2 kJ mol^?1 and ΔS^≠=?147.4 kJ mol^?1 K^?1. The largely negative ΔS^≠ value suggests the involvement of a seven‐coordinate species with the strongly coordinated acetonitrile molecule in the transition state. Thus, the strength of the coordination of the solvent molecule to the Ru^II center is a determinant factor in the photoisomerization of the Ru^II–pterin complex.     

Synthesis,characterization and catalytic studies of ruthenium(II) chalconate complexes

Stable ruthenium(II) carbonyl complexes of the type [RuCl(CO)(EPh₃)(B)(L)] (E = P or As; B = PPh₃, AsPh₃ or Py; L = 2′‐hydroxychalcones) were synthesized from the reaction of [RuHCl(CO)(EPh₃)₂(B)] (E = P or As; B = PPh₃, AsPh₃ or Py) with 2′‐hydroxychalcones in benzene under reflux. The new complexes were characterized by analytical and spectroscopic (IR, electronic ¹H, ³¹P and ¹³C NMR) data. They were assigned an octahedral structure. The complexes exhibited catalytic activity for the oxidation of primary and secondary alcohols into their corresponding aldehydes and ketones in the presence of N‐methylmorpholine‐N‐oxide (NMO) as co‐oxidant and were also found to be efficient transfer hydrogenation catalysts. Copyright © 2008 John Wiley & Sons, Ltd.     

Synthesis,characterization, and catalytic activity of a polymer-supported copper(II) complex with a thiosemicarbazone ligand

A thiosemicarbazone Cu(II) complex anchored to a polystyrene framework has been synthesized and characterized by analytical and spectroscopic techniques. The complex was found to be a highly active catalyst for the oxidation of various organic substrates including alkenes and alcohols using H₂O₂ as oxidant. The reaction conditions were optimized with respect to temperature, solvent, oxidant, catalyst amount, and substrate to peroxide ratio. The heterogeneous catalyst was reused five times without significant loss of activity. A comparison between the catalytic activities of this polymer-supported Cu(II) complex and its homogeneous analogue was carried out.     

A potent ruthenium(II) antitumor complex bearing a lipophilic levonorgestrel group

The novel steroidal conjugate 17-α-[2-phenylpyridyl-4-ethynyl]-19-nortestosterone (LEV-ppy) (1) and the steroid-C,N-chelate ruthenium(II) conjugate [Ru(η(6)-p-cymene)(LEV-ppy)Cl] (2) have been prepared. At 48 h incubation time, complex 2 is more active than cisplatin (about 8-fold) in T47D (breast cancer) and also shows an improved efficiency when compared to its nonsteroidal analogue [Ru(η(6)-p-cymene)(ppy)Cl] (ppy = phenylpyridine) (3) in the same cell line. The act of conjugating a levonorgestrel group to a ruthenium(II) complex resulted in synergistic effects between the metallic center and the steroidal ligand, creating highly potent ruthenium(II) complexes from the inactive components. The interaction of 2 with DNA was followed by electrophoretic mobility. Theoretical density functional theory calculations on complex 2 show the metal center far away from the lipophilic steroidal moiety and a labile Ru-Cl bond that allows easy replacement of Cl by N-nucleophiles such as 9-EtG, thus forming a stronger Ru-N bond. We also found a minimum energy location for the chloride counteranion (4(+)·Cl(-)) inside the pseudocavity formed by the α side of the steroid moiety, the phenylpyridine chelating subsystem, and the guanine ligand, i.e., a host-guest species with a rich variety of nonbonding interactions that include nonclassical C-H···anion bonds, as supported by electrospray ionization mass spectra.