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Hydrogen gas generation with an effective response to changing application demands was achieved with the use of a hydrogen storage battery based on aqueous cesium bicarbonate hydrogenation/formate dehydrogenation, homogeneously catalyzed by an Ir(I) N-heterocyclic carbene complex. In this device, the storage solution was circulated through a small volume tubular reactor heated to the required high temperature to allow fast hydrogen evolution while the high volume reservoir was kept at ambient temperature at which no H2 was generated. Merely by the control of the reactor temperature, it was possible to regulate the rate of hydrogen evolution as required. The results also demonstrate the feasibility of homogeneous catalysis for the purpose of hydrogen generation in flow systems.

The highly selective formation of cinnamalcohol in hydrogenation of trans-cinnamaldehyde with [{RuCl2(mtppms)2}2] + mtppms as catalyst (mtppms = monosulfonated triphenylphosphine) in aqueous solution was substantially accelerated by NaHCO3 (in 20–50 mol% quantities relative to cinnamaldehyde). More than double conversion compared to bicarbonate-free systems was observed at n(NaHCO3)/n(Ru) = 20. Prehydrogenation of the reaction mixture before the addition of cinnamaldehyde resulted in further rate increase (45.3% conversion vs. 13.1% in water). 1H , 13C and 31P NMR studies revealed that formate produced in hydrogenation of bicarbonate facilitated formation of trans-[Ru(H)2(H2O)(mtppms)3], a better catalyst than cis-fac-[Ru(H)2(H2O)(mtppms)3] which is the product of the reaction of [{RuCl2(mtppms)2}2] + mtppms with H2 in the absence of formate (or bicarbonate). Accordingly, NaHCO2 produced even higher rate increase than the same amount of NaHCO3.

Five new complexes of the type [RuCl2(NHC)(η6-arene)] (4, 5, and 6) and [RuCl(NHC)(η6-arene)(PR3)]Cl (7 and 8) (NHC N-heterocyclic carbene = bmim, emim; arene = benzene, p-cymene; PR3 = PPh3 or pta = 1,3,5-triaza-7-phosphaadamantane) were synthetized and applied as catalysts (together with the known [RuCl2(bmim)(η6-p-cymene)] (3) with and without added PPh3) in racemization of optically active secondary alcohols in toluene. The highest catalytic activity, TOF = 9.3 h−1 (ee as low as 1.3% in 4 h at 95 °C) was observed in racemization of (S)-1-phenylethanol with a catalyst (4 mol%) prepared in situ from 3 and 1 equivalent of PPh3. It is of practical significance that formation of acetophenone byproduct was suppressed to 3.5% by 17% v/v isopropanol in toluene. DFT calculations revealed that the rate determining step in the suggested reaction mechanism was the agostic coordination of hydrogen on the chiral carbon atom of the alcohol substrate.

The newly synthesized mer-trans-[RuCl2(OH2)(PTA)3] (1) is the first compound isolated in solid state containing the Ru(PTA)3-fragment (PTA = 1,3,5-triaza-7-phosphatricyclo[3.3.1.13,7]decane). Dissolution of 1 in aqueous HCl leads to mer-[RuCl3(HPTA)3]Cl2 (2) which is stable in the dark but is transformed into fac-[RuCl3(HPTA)3]Cl2 (3) under visible light. Irradiation with visible light of an aqueous solution of 1 at room temperature or refluxing of the same solution in the dark leads to the formation of [{Ru(PTA)3}2(μ-Cl)3]Cl (4). The dinuclear complex 4 was also formed upon irradiation of solutions of PTA and various Ru(II)-complexes ([RuCl2(DMSO)4], [{RuCl2(η6-p-cymene)}2]) or cis-cis-trans-[RuCl2(DMSO)2(PTA)2]). All complexes were characterized by elemental analysis and NMR spectroscopy, furthermore solid state structures of 2·1.25H2O, 3·HCl·2H2O and 4·9H2O were also determined by single crystal X-ray diffraction. We have investigated the influence of the above photochemical processes on reduction of benzaldehyde and cinnamaldehyde with trans-[RuCl2(PTA)4] and cis-cis-trans-[RuCl2(DMSO)2L2] (L = PTA, (PTA-Me)CF3SO3, (PTA-Bn)Cl; Me = methyl, Bn = benzyl) complexes as catalysts. The effect of visible light on benzonitrile hydration with various Ru(II)-PTA catalysts is also reported.

In this work we have found, that the water-soluble cis,mer-[IrH2Cl(mtppms)3] (mtppms = monosulfonated triphenylphosphine Na-salt) was an excellent catalyst for reduction of terminal alkynes by hydrogen transfer from aqueous HCOOH/HCOONa mixtures. The conversions strongly depended on the pH of the reaction mixtures, and the highest rate of phenylacetylene transfer hydrogenation was observed at pH 3. The same dihydrido-Ir(III) complex actively catalyzed also the hydrogenation of terminal alkynes under mild conditions (T = 50 °C; P(H2) = 2–10 bar). Importantly, both the hydrogenation and hydrogen transfer reductions afforded exclusively the corresponding alkenes as products. Phenylacetylene and its substituted derivatives reacted smoothly, while benzylic and aliphatic alkynes were less reactive or did not react at all. It was also found, that an excess of the mtppms ligand inhibited the reaction. This was rationalized by formation of cisz-[IrH2(mtppms)4]+ which was also confirmed with multinuclear NMR spectroscopy. On the basis of the experimental results, a joint mechanism was suggested for both the hydrogenation and transfer hydrogenation pathways. The mechanism of hydrogenation and transfer hydrogenation of phenylacetylene was also studied by DFT calculations, which revealed several possibilities for protonation of a vinyl intermediate as the crucial step in formation of the styrene product.

1,3,5-Triaza-7-phosphaadamantane (pta, phosphaurotropine) played a special role in the development of aqueous organometallic chemistry and catalysis. The main reason is in its easy synthesis, oxidation stability, versatile possibilities of functionalization, and high solubility not only in water but also in several common organic solvents. Such favourable solubility behaviour allowed straightforward synthesis of pta-containing transition metal complexes from simple, inexpensive, often commercial starting materials. A further advantage of pta and its complexes is in their pronounced tendency to crystallize which allowed determination of solid-state structures of a great number of such compounds. This review covers synthetic procedures of ruthenium(II)-complexes with pta, and N-alkyl-pta derivatives as ligands, as well as their most important reactions in aqueous systems. Ru(II)-pta complexes were employed as catalysts in several important aqueous-phase processes such as selective hydrogenation and transfer hydrogenation of aldehydes, hydration of nitriles, and redox isomerization of allylic alcohols. Hydrogenation of carbon dioxide/bicarbonate and dehydrogenation of formic acid/aqueous formate were also studied with various Ru(II)-complexes of phosphaurotropines. Altogether the results described in this review made a significant positive impact on the development of green chemical processes.

A new, solvent-free method has been developed for the synthesis of 7-(2-carboxy-ethyl)-1,3,5-triaza-7-(phosphoniatricyclo)[3.3.1.13,7]decane (L). It is disclosed here that 1,3,5-triaza-7-phosphaadamantane (PTA) reacted cleanly with acrylic acid in a planetary ball mill resulting in 88% yield of the corresponding P-carboxy-ethyl derivative, in striking contrast to the complete failure of the synthesis of the same product from the same reactants in solution. The resulting phosphabetaine, L gave crystalline 1D coordination polymers with Ag+-salts bearing PF 6 - , p-toluenesulfonate (tos) and trifluoromethanesulfonate (OTf) anions. According to single-crystal X-ray diffraction studies, the solid state structures of these coordination polymers were decisively influenced by the anion of the Ag+-salt used for synthesis. In addition to single-crystal X-ray diffraction, the new Ag-based coordination polymers, namely [Ag(μ3-L-κ3N:O:O’)]n(PF6)n, (1), [Ag(tos)(μ3-L-κ3N:N:O)]n·nH2O, (2), and [Ag(OTf)(μ3-L-κ3N:O:O’)]n, (3) were characterized also by elemental analysis, 1H-, 13C-, and 31P NMR, as well as IR spectroscopies and with ESI mass spectrometry. Determination of the hydrodynamic diameter of the phosphabetaine ligand and its Ag+-complexes by diffusion NMR measurements revealed, that upon dissolution in water these compounds did not retain their polymeric nature.

The water-soluble [RuCl2(pta)(η6-p-cymene)] (pta = 1,3,5-triaza-7-phosphaadamantane) was applied as catalyst in the transposition of allylic alcohols, such as oct-1-en-3-ol in aqueous media. The isomerisation of oct-1-en-3-ol to octan-3-one took place only at pH > 10 buffer solutions or in the presence of alkali metal carbonates. The aqueous solution of “in situ” catalyst ([RuCl2(pta)(η6-p-cymene)] + 2 eq Na2CO3) could be reused in the biphasic isomerization of oct-1-en-3-ol for at least five times without a significant loss of the catalytic activity. It was demonstrated that carbonate is not only a base in this reaction but leads to formation of a highly active catalyst, [Ru(η2-O2CO)(pta)(η6-p-cymene)]. This compound was isolated as crystalline solid and characterized in detail (including X-ray diffraction).

The formation of hydride derivatives of sulfonated palladium(II) salan (hydrogenated salen) complexes was studied with DFT methods. The non-hydrolytic property, chirality, and flexibility lead to a significant difference compared to salen derivatives. We made a detailed computational study to understand the relevance of the flexibility in contrast to the rigid salen complex. Two main pathways were investigated: one of them was a direct monohydride formation where the oxygen of the phenolate group was substituted by a hydrogen molecule followed by a proton transfer. Another was an indirect monohydride formation involving the substitution of phenolate arm by a solvent water molecule in the first step and subsequent reaction with H2 in the second. We focused on weak interactions among the Pd-complex and water molecules. Trigonal, square, and diamond motifs of H-bond networks were found around the oxygen atom of the phenolate arm which is crucial during the proton transfer step, however, substitution steps prefer chain type motifs.

The recently synthesized water-soluble Na2[Pd(HSS)] (Na2HSS = hydrogenated sulfonated salen) was shown to be a non-toxic, active catalyst for modification of model and biomembranes by homogeneous catalytic hydrogenation. Hydrogenation of the unsaturated fatty acyl residues in soy-bean lecithin liposomes and in biomembranes of intact Pseudomonas putida F1 cells was accompanied by substantial cis-trans isomerization around the C C double bonds. The hydrogenations could be run in aqueous media under mild conditions (25 °C, 1 bar H2). Partial saturation (up to 10% conversion) of the membrane lipids of P. putida F1 did not damage the cells.

An environment-friendly, convenient, fast and solvent-free mechanochemical approach have been accomplished for the synthesis of several diimidazolium salts and the bridging dinuclear rhodium(I)–N-heterocyclic carbene complexes of the type [{RhCl(cod)}2(μ-di-NHC)] derived from them. The compounds were synthesized also by the classical solvent method and the results of the two approaches were compared. A systematic study of both the mechanochemical and the solvent syntheses has also been carried out to determine the effects of various factors influencing the reactions. This is the first report on the mechanochemical synthesis of poly-NHC metal complexes as well as NHC–Rh complexes in ball mill.

The catalytic activity of [RuClCp(HdmoPTA)(PPh3)](OSO2CF3) (1) and the dimeric complexes [RuClCp(PPh3)-μ-dmoPTA-1κP:2κ2N,N'-MCl2] (M = Ni (2), Co (3), Zn (4)) for the isomerization in water under Ar and ambient atmosphere of 1-octen-3-ol, 1-hepten-3-ol and 1-hexen-3-ol was investigated. A detailed study was devoted to the catalytic activity under Ar of 1 for the isomerization of 1-octen-3-ol.

Unsaturated aldehydes were efficiently reduced by transfer hydrogenation from sodium formate in water–2-propanol mixtures using a water-soluble Ru(II)-tertiary phosphine catalyst. The reaction yielded unsaturated alcohols with complete selectivity and without hydrogenation or isomerization of C C bonds of the substrates. Very high reaction rate was observed in the transfer hydrogenation of cinnamaldehyde already at 30 °C with turnover frequency of 160 h−1 and this increased to 3800 h−1 at 70 °C. Consequently, the method is applicable to the synthesis of unsaturated alcohols in case of heat sensitive or highly volatile aldehydes, too. Based on multinuclear NMR investigations, trans-[RuH2(H2O)(mtppms)3] is suggested as the key catalytic species.

With the aim of identifying new types of water-soluble catalyst precursors for modification of biological membranes by homogeneous hydrogenation in aqueous solution and under mild conditions, we have performed detailed equilibrium and spectroscopic characterization of complex formation between nickel(II) or palladium(II) and salan-type ligands sulfonated in their aromatic rings (N,N′-bis(2-hydroxy-5-sulfonatobenzyl)-1,4-diaminoethane (HSS), N,N′-bis(2-hydroxy-5-sulfonatobenzyl)-1,4-diaminopropane (PrHSS) and N,N′-bis(2-hydroxy-5-sulfonatobenzyl)-1,4-diaminobutane (BuHSS)) in the slightly acidic–alkaline pH range. The stability constants of the metal complexes were determined using pH-potentiometry. The catalytic activities of the [Ni(HSS)] and [Pd(HSS)] complexes in hydrogenation and redox isomerization of oct-1-en-3-ol were also studied. The results indicate, that all of the investigated ligands exhibit excellent nickel(II) and palladium(II) binding ability via the formation of (O−,N,N,O−) linked chelate system. Both [Ni(HSS)] and [Pd(HSS)] catalyze the hydrogenation and redox isomerization of oct-1-en-3-ol. [Pd(HSS)] shows excellent activity and the reaction was highly selective to the formation of octan-3-ol. [Ni(HSS)] is also an active and selective catalyst for this hydrogenation reaction and to the best of our knowledge, [Ni(HSS)] is the first nickel(II)-based, hydrolytically stable, water-soluble catalyst bearing sulfonated salan moiety.

Ground state optimizations and excited state calculations were performed to analyze the possible anionic forms of Alizarin Red S(ulphonated) and its ML2 type metal complexes formed with palladium(II). Six functionals have been tested (B3LYP, M06-2X, M06, BH&HLYP, PBE0, LC-wPBE, and CAM-B3LYP) with two basis sets (6-311+g(d,p) and TZVP). The relative errors of these functionals in reproducing the experimental UV-Vis absorption wavelengths are reported for the energetically lowest lying isomers. It was found that the degree of deprotonation affects several functionals in a systematic way. M06 and CAM-B3LYP xc-functionals gave the best estimates according to the average relative errors. These two functionals were then used to explore the coordination mode (hydroxy-keto or catechol) of the palladium(II) complexes and the effect of (de)protonation. © 2014 Elsevier B.V.

The discovery and development of N-heterocyclic carbenes is no doubt one of the biggest success stories in the era of modern chemistry. In the last three decades, poly-N-heterocyclic carbenes have received increasing attention and a large number of reports have been published on the use of poly-NHC complexes in water. This paper is aimed to provide an overall review on poly-N-heterocyclic carbene complexes that are either water-soluble or have applications in aqueous media or both. The first two sections of the review are related to the types and general structural properties of poly-NHCs. The next part deals with the general advantages of using water and the last two sections are about poly-NHC complexes in aqueous media and their applications in various fields including catalysis, photophysics and medicine.

The water-soluble carbene ligand precursors sIMesH + Cl − and sSIMesH + Cl − were synthesized in high yields by direct sulfonation of IMesH + Cl − (1,3-bis(2,4,6-trimethylphenyl) imidazolium chloride) and SIMesH + Cl − (1,3-bis(2,4,6-trimethylphenyl)imidazolinium chloride). Gold(I)-N-heterocyclic carbene complexes [AuCl(sIMes)] and [AuCl(sSIMes)] were prepared by carbene transfer from the zwitterionic [Ag(sIMes) 2 ] and [Ag(sSIMes) 2 ] to [AuCl(tht)] (tht = tetrahydrothiophene). In methanol–water mixtures or in neat water, the new gold(I)–NHC complexes showed high catalytic activity in Markovnikov type hydration of terminal alkynes (up to a turnover frequency 1990 h −1 ; ethynyltoluene, 0.1 mol% catalyst) but were markedly less active in case of internal alkynes (TOF = 3.6 h −1 ; diphenylethyne, 1 mol% catalyst). These new Au(I)-NHC catalysts do not require acid co-catalysts or activation by Ag(I)-additives.

A simple and efficient synthesis of amides by selective hydration of aromatic and aliphatic nitriles is described. The catalysts are prepared in situ from easily available Ru-precursors and ligands using water as the solvent. The most active catalyst, is obtained from [RuCl 2 (dmso) 4 ] and benzylated 1,3,5-triaza-7-phosphaadamantane. Of the 16 substrates examined, 92–99% conversions of 14 nitriles were achieved in one hour at reflux temperature.

In aqueous solutions at 80 °C, [RuClCp(mPTA)2](OSO2CF3)2 (1) and [RuCp(mPTA)2(OH2-κO)](OSO2CF3)3·(H2O)(C4H10O)0.5 (3) (mPTA: N-methyl-PTA) were found effective catalysts of the redox isomerization of alk-1-en-3-ols to the corresponding ketones, characterized by initial turnover frequencies (TOF) of 162 h−1 (3) and 9.6 h−1 (1) in 1-octen-3-ol isomerization. A sharp maximum of the reaction rate as a function of pH was observed with 1 in phosphate buffer solutions. Kinetic and 31P NMR measurements revealed for the first time in aqueous organometallic catalysis that component(s) of phosphate buffer (most probably HPO42−) strongly interact(s) with the catalyst complexes and this interaction leads to a dramatic loss of the catalytic activity.

Water-soluble ruthenium(II) and rhodium(I) complexes containing monosulfonated triphenylphosphine (mtppms) ligands were immobilized on commercially available anion-exchangers. The resulting solid catalysts were suitable for use in a microfluidics-based flow reactor (H-Cube™) of high throughput capability. With the heterogenized [{RuCl2(mtppms)2}2] disubstituted alkynes were hydrogenated to cis-alkenes with up to 85% selectivity, while the use of the immobilized [RhCl(mtppms)3] yielded 1,2-diphenylethane as the major product. The ruthenium catalyst also reduced trans-cinnamaldehyde to 3-phenylpropanal selectively and catalyzed the isomerization of 1-octen-3-ol to octan-3-one. This simple and versatile method of the immobilization of water-soluble complexes yields active and durable molecularly dispersed yet solid catalysts.

Allyl alcohols were isomerized to ketones or aldehydes in aqueous–organic biphasic systems using a water-soluble N-heterocyclic carbene complex [RuCl2L(η6-p-cymene)] (L = 1-butyl-3-methyl-imidazolin-2-ylidene, p-cymene = p-isopropyltoluene) for the first time. Hydrogen is needed to initiate the reaction and isomerization is accompanied by hydrogenation to the saturated alcohol. Initial turnover frequencies up to 65 mol product/mol catalyst · h were observed in neutral solutions at 80 °C. The reactions were strongly influenced by the pH of the aqueous phase. Addition of NaCl improved the total conversions and favoured isomerization on the expense of hydrogenation. The catalyst could be recycled in the aqueous phase for at least four times without a significant change in activity and selectivity.

Density functional theory along with a dielectric continuum solvation model has been applied to identify possible reaction intermediates for the catalytic hydrogenation of HCO 3 − anion into HCO 2 − that occurs in aqueous solutions in the presence of water-soluble ruthenium complexes. Bicarbonate ion is shown to coordinate to a Ru-dihydride species, which then undergoes a protonation process that yields a CO 2 complex. The C H bond formation is found to take place via CO 2 insertion into a Ru H bond and the direct elimination of the formate product is shown to be an energetically favored step, which is assisted by the water medium. We find that water is directly involved in the reaction as a protonating/deprotonating agent and also acts as a coordinating ligand.

Homogeneous hydrogenation of carbon dioxide continues to attract interest in the hope of finding active and selective catalysts for the production of valuable organics based on this cheap and abundant carbon source. This review covers advances published or in press since 1995. The survey of the field shows that while very active catalysts and co-catalysts have been discovered in this period for the production of formic acid and its derivatives, there has been only preliminary development of homogeneous catalysts for the production of other oxygenates (e.g. methanol, CO) and C n -compounds ( n > 1).

Aqueous suspensions of calcium carbonate were hydrogenated to yield calcium formate under a gas phase containing both H2 and CO2. A rhodium(I)-complex of monosulfonated triphenylphosphine (mtppms), [RhCl(mtppms)3] was used as catalyst. Reaction temperatures were in the range of 20–70 °C, total pressure 10–100 bar with an optimum p(CO2):p(H2) ratio of 1:4. Due to the mobile bicarbonate-formate equilibrium, the highest available formate concentration is decreased with increasing temperature but increased with increasing pressure. Interestingly, at 50 °C and 100 bar total pressure the yield of formate was 143% (based on CaCO3) which implies the formation of free formic acid in the reaction of CO2 from the gas phase. The dependence of the hydrogenation rate on the catalyst and ligand concentrations, as well as that of the decomposition of formate as a function of temperature were also studied.

The heterogenized versions of [RuCl 2 (PPh 3 ) 3 ] and [{RuCl 2 (TPPMS) 2 } 2 ] were prepared and applied in the selective hydrogenation of α , β -unsaturated aldehydes. Depending on the conditions the above heterogenized catalysts could hydrogenate selectively either the C O or the C C bonds, similar to the results obtained in aqueous biphasic systems. Meanwhile the heterogenized catalysts show all the advantages that we can expect from a heterogeneous catalyst: good performance, easy separation, and the possibility of recycling. The effect of H 2 pressure on the selectivity was also studied.

The water-soluble Ru(II)-phosphine complex, [{RuCl2(mTPPMS)(2)}(2)] was found a suitable catalyst for the hydrogenation of NaHCO3 to NaHCO2 in aqueous solution under mild conditions with catalyst turnover frequencies (TOFs) in the range of 35-50 h(-1) at 50degreesC and 10 bar total pressure. The suggested reaction mechanism involves the formation of Ru(II)-hydrides of the general formula [RuHX(mTPPMS)(4)] where X = H-, HCO3- or HCO2-. At 80degreesC and 95 bar total pressure, the reduction of NaHCO3 proceeded with high reaction rate (9600 h(-1)) hitherto unobserved in purely aqueous solutions. The reactions do not require the presence of organic amine additives, however, the addition of quinoline increased the rate considerably. Aqueous suspensions of calcium carbonate could also be hydrogenated with CO2/H-2 gas mixtures. (C) 2003 Elsevier B.V. All rights reserved.

The new water-soluble ruthenium-nitrosyl complexes [RuCl3(NO)(TPPMS)(2)] and [RuCl3(NO)(TPPTS)(2)] were synthetized and characterized by IR, H-1 and P-31 NMR spectroscopies. The NO stretching frequencies, nu(NO) = 1870 cm(-1) (TPPMS) and 1883 cm(-1) (TPPTS) suggest a linear Ru-N-O arrangements. Reactions with OH- yield the corresponding [RuCl3 (NO2)(P)(2)] derivatives, furthermore, [RuH(NO)(P)(3)] is formed with TPPMS or TPPTS, respectively, under 100 bar H-2 pressure. The new complexes are suitable precatalysts for the hydrogenation of carbon dioxide and/or bicarbonate in aqueous solutions up to a turnover frequency of 400 h(-1) under relatively mild conditions (30 bar H-2, 70 degreesC). (C) 2003 Elsevier Science B.V. All rights reserved.

Mixtures of polar lipids were hydrogenated using the palladium-bis(alizarin monosulfonate) catalyst and the product mixtures were analyzed by MALDI-TOF mass spectrometry in order to determine the individual reactivity of the constituent lipids. In their binary mixtures, dioleyl phosphatidyl choline and dioleyl phosphatidyl ethanolamine showed the same reactivity. Addition of cholesterol slowed down the hydrogenation of these two lipids by about the same extent. Conversely, in the mixture of lipids isolated from the thylakoid of the blue-green alga Synechocystis PCC 6803 , monogalactosyl and digalactosyl diacyl glycerols (MGDG and DGDG, respectively) reacted twice as fast as sulfolipids (SL) and phosphatidyl glycerol (PG).

Reperfusion-induced ventricular fibrillation (VF) and heme oxygenase (HO)-related carbon monoxide (CO) production in isolated ischemic/reperfused rat hearts were studied by gas chromatography. Hearts were subjected to 30 min ischemia followed by 2 h reperfusion, and the expression of HO-1 mRNA (about 4-fold) was observed in ischemic/reperfused-nonfibrillated hearts. In fibrillated hearts, the reduction (about 75%) in HO-1 mRNA expression was detected. These changes in HO-1 mRNA expression were reflected in tissue CO production. Thus, in the absence of VF, CO production was increased about 3.5-fold, while in the presence of VF, CO production was under the detectable level in comparison with the control group. Our results suggest that the stimulation of HO-1 mRNA expression may lead to the prevention of reperfusion VF via an increase in endogenous CO production. To prove this, hearts were treated with 1 μM of N-tert-butyl-α-phenylnitrone (PBN) as an inducer of HO-1. PBN treatment resulted in about 20 times increase in HO-1 mRNA expression, and even a higher production rate in endogenous CO. HO protein level and enzyme activity followed the same pattern, as it was observed in HO-1 mRNA expression, in fibrillated and nonfibrillated myocardium. Five mM/l of zinc-protoporphyrin IX (ZnPPIX) significantly blocked HO enzyme activity and increased the incidence of VF, therefore the application of ZnPPIX led to a significant reduction in HO-1 mRNA and protein expression. Our data provide direct evidence of an inverse relationship between the development of reperfusion-induced VF and endogenous CO production. Thus, interventions that are able to increase tissue CO content may prevent the development of reperfusion-induced VF.

Free formic acid was produced in hydrogenation of carbon dioxide dissolved in aqueous sodium formate solutions under H(2) and CO(2) pressure with the water-soluble rhodium-phosphine complex, [RhCl(mtppms)(3)] (mtppms = monosulfonated triphenylphosphine) as catalyst. Concentration of sodium formate, total gas pressure and the pressure ratio of H(2) to CO(2) were the most important factors for production of HCOOH. Up to 0.13 M concentration of HCOOH was achieved, while there was negligible formic acid production in the absence of sodium formate. (C) 2011 Elsevier B.V. All rights reserved.

In aqueous solutions, [RuCl2(TPPMS)(2)](2) (TPPMS = 3-sulfonatophenyldiphenylphosphine) catalyzes the exchange between H-2 and D2O or between D-4 and H2O with high efficiency (up to 1 252 turnovers per hour) under mild conditions (298 K, 2 MPa H-2). The exchange rate strongly depends on the solution pH. Similar H/D exchange is observed with the water soluble tertiary phosphine complexes [RhCl(TPPMS)(3)], [RhCl(TPPTS)(3)] and [RuCl2(PTA)(4)] as catalysts (TPPTS = tris(3-sulfonatophenyl)phosphine. PTA = 1,3,5-triaza-7-phosphadamantane) which, however, show lower activity. (C) 2000 Academie des sciences / Editions scientifiques et medicales Elsevier SAS (C) 2000 Academie des sciences / Editions scientifiques et medicales Elsevier SAS.

The new complexes (RRuSC, SRuSC)-[(η6-pCym)Ru(l-Aze)Cl] (6a, b), (RRuSC, SRuSC)-[(η6-pCym)Ru(l-Pip)Cl] (7a, b), (RRuRRuRRuSCSCSCSNSNSN, SRuSRuSRuSCSCSCSNSNSN)-[{(η6-pCym)Ru(l-Aze)}3](BF4)3 (8a, b) and (RRuRRuRRuSCSCSCSNSNSN, SRuSRuSRuSCSCSCSNSNSN)-[{(η6-pCym)Ru(l-Pip)}3](BF4)3 (9a, b) (l-Aze=l-2-azetidinecarboxylate, l-Pip=l-2-piperidinecarboxylate) were prepared, characterized and used, together with the known [{(η6-pCym)Ru(l-Pro)}3](BF4)3, 5 and [{(η6-pCym)Ru(l-Ala)}3](BF4)3, 10 (l-Pro=l-prolinate, l-Ala=l-alaninate), in hydride transfer reduction of acetophenone, a series of substituted acetophenones and several other ketones with moderate to high conversions and enantioselectivities up to 86% e.e.

The water-soluble chlorotris(1,3,5-triaza-7-phosphaadamantane)rhodium(I), [RhCl(PTA) 3 ], was successfully employed for hydrogenation of phospholipid liposomes as model membranes in aqueous media under mild conditions. The highest conversion was achieved at pH 4.70. Formation of asymmetrically dideuterated lipids, together with isomerization and kinetic results revealed the important role of reversible formation of an alkyl-rhodium intermediate in the mechanism.

This paper describes Western-blotting evidence for the presence of various guanine nucleotide binding proteins, G-proteins in cultured rat cerebral endothelial cells (CECs) and two immortalized cerebral endothelial cell lines, RBE4 and GP8. By using specific antibodies raised against known sequences of appropriate G-protein types that were previously characterized, we demonstrated the presence of Gsalpha, Gi2alpha, Gi3alpha, Gq/11alpha, Goalpha and Gbeta in cell lysates of primary cultures of CECs, and plasma membranes of RBE4 and GP8 cells. The appearance of Goalpha proteins in CECs might be of special importance, since they were not detected in peripheral endothelial cells in previous studies. Isoproterenol and bradykinin displayed significant, dose-dependent stimulation of [35S]GTPgammaS binding above basal values. This assay, reflecting the GDP-GTP exchange reaction on Galpha-subunits by receptor agonists, suggested that there were functional, G-protein coupled beta-adrenergic and bradykinin receptors in these systems. No significant stimulation of [35S]GTP7gammaS binding was noted with serotonin under our experimental conditions. Since stimulation of [35S]GTPgammaS binding by isoproterenol and bradykinin was additive, it was concluded that different Galpha proteins were activated by these two ligands. In analogy to other systems, activation of Gs is most likely by isoproterenol, while Gi and/or Gq/11 proteins might be activated by bradykinin receptors. The possible significance of the receptors and G-proteins detected is being discussed in the functioning of cerebral endothelium, and thus the blood-brain barrier.

The effect of pH on the formation and equilibrium distribution of the water soluble ruthenium hydrides [HRuCl(TPPMS) 2 ] 2 , [HRuCl(TPPMS) 3 ] and [H 2 Ru(TPPMS) 4 ] (TPPMS=(3-sulfonatophenyl)diphenylphosphine sodium salt) was studied in aqueous solution by pH-potentiometric and 1 H and 31 P NMR methods. Depending on the pH, [RuCl 2 (TPPMS) 2 ] 2 and its hydrido-derivatives hydrolyse extensively, giving rise to formation of hydroxo-ruthenium complexes. It was established that at pH≤3.3 the dominant ruthenium(II) species was [HRuCl(TPPMS) 3 ], while at pH≥7 it was [H 2 Ru(TPPMS) 4 ]. While [HRuCl(TPPMS) 3 ] catalyzed the slow, selective hydrogenation of the CC bond in trans -cinnamaldehyde, [H 2 Ru(TPPMS) 4 ] was found an active and selective catalyst for CO reduction. Consequently, the selectivity of the hydrogenation of trans -cinnamaldehyde could be completely inverted by minor changes in the solution pH, shifting the equilibrium between [HRuCl(TPPMS) 3 ] and [H 2 Ru(TPPMS) 4 ].

The relationship between phospholipid saturation and membrane physical structure in a complex, highly polyunsaturated biological membrane (trout liver microsomes) has been studied by the graded and specific hydrogenation of polyunsaturated fatty acids. The homogeneous catalyst Pd(QS)2 caused rapid and effective hydrogenation, increasing the proportion of saturated fatty acids from 20-30% up to 60%, without loss or fragmentation. Long chain, polyunsaturated fatty acids (20:5 omega 3, 22:6 omega 3) were rapidly converted to a large number of partially hydrogenated isomers, and ultimately to the fully saturated C20 or C22 fatty acids. C18 mono- and di-unsaturates showed slower rates of hydrogenation. Increased saturation was closely associated with an increased membrane physical order as determined by the fluorescence anisotropy probe, 1,6-diphenyl-1,3,5-hexatriene. However, extensive hydrogenation led to highly ordered membranes exhibiting a gel-liquid crystalline phase transition between 30 and 60 degrees C. Polyunsaturated membranes can thus be converted into partially or substantially saturated membranes with measurable phase structure without direct alteration of other membrane components. This offers a less equivocal means of assessing the influence of polyunsaturation upon membrane structure and function.

Aqueous dispersions of PVP-protected Pd, Pt, Rh, PdPt and PdRh colloids (PVP=poly(2-vinylpyrrolidone)) were successfully applied for the catalytic hydrogenation of water soluble olefins and liposomes as models of biological membranes. The metal-PVP particles were anchored onto the surface of water insoluble, crosslinked poly(2-vinylpyrrolidone), PVPP. Both the sols and the supported catalysts are stable in time, non-permeable to the lipid membrane, and can be separated completely from the reaction mixture by decantation or centrifugation.

The vertebrate olfactory system has long been an attractive model for studying neuronal regeneration and adaptive plasticity due to the continuous neurogenesis and synaptic remodelling throughout adult life in primary and secondary olfactory centres, its precisely ordered synaptic network and accessibility for manipulation. After homotopic transplantation of fetal olfactory bulbs in bulbectomized neonatal rodents, newly regenerated olfactory neurons form glomeruli within the graft, and the efferent mitral/tufted cells of the transplant innervate the host brain, terminating in higher olfactory centres. However, the synaptic connections of the transplanted relay neurons within the graft and/or host's olfactory centres could not be characterized mainly because of lack of suitable cell-specific markers for these neurons. In this study, we have used olfactory bulbs from transgenic fetuses, in which the majority of the mitral/tufted cells express the bacterial enzyme beta-galactosidase, for homotopic olfactory bulb transplantation following complete unilateral bulbectomy. In the transplants, the cell bodies and terminals of the donor mitral/tufted cells were identified by beta-galactosidase histochemistry and immunocytochemistry at both light and electron microscope levels. We demonstrate that transplanted relay neurons re-establish specific synaptic connections with host neurons of the periphery, source of the primary signal and central nervous system, thereby providing the basis for a functional recovery in the lesioned olfactory system.

C–X bonds in carbon tetrachloride, chloroform and 1-hexyl halogenides were transformed into C–H bonds in a transfer hydrodehalogenation reaction catalyzed by water soluble ruthenium(II) phosphine complexes. A turnover frequency of up to 1000 h−1 can be achieved when an aqueous solution of sodium formate is the hydrogen donor and RuCl2(TPPMS)2 (1) the catalyst (TPPMS=m-sulfophenyl diphenylphosphine sodium salt).

A survey of the literature published in 1995 and partly in 1994 on organometallic chemistry and catalysis shows that the field is characterized by further dynamic progress in research of industrially relevant processes, such as hydroformylation, in extension of aqueous organometallic catalysis to more and more diverse laboratory syntheses and in understanding the mechanisms of such processes.

Free radicals have been implicated in the pathogenesis of vasogenic brain edema caused by ischemic or traumatic injury. It has been reported that in transgenic mice overexpressing the human CuZn-superoxide dismutase, brain edema is decreased in many cerebral disorders. To investigate the effects of free radicals on the permeability of the blood—brain barrier, we established an in vitro model system of the blood—brain barrier using brain endothelial cells cultivated from transgenic mice and non-transgenic mice. The blood—brain barrier model is originated by a monolayer of brain endothelial cells cultured on a membrane which has 0.45-μm pores. Electrical resistance across the cell monolayer, which reflects the paracellular flux of ionic molecules, was measured. The blood—brain barrier models were incubated with menadione (vitamin K3, an intracellular O−2 producing agent), and segmental changes in the electrical resistance across the monolayer were compared between the transgenic and the non-transgenic mice. Superoxide dismutase activity of the cultured brain endothelial cells was 1.7 times higher in the transgenic than in the non-transgenic mice (n = 3, P < 0.001). The electrical resistance was reduced by menadione in the transgenic but not in the non-transgenic mice (n = 7, P < 0.05) in the early stage. Moreover, desferroxamine mesylate (Fe2+ chelating agent) inhibited the menadione-induced early decrease in electrical resistance in the transgenic mice (n = 7, P < 0.05). These results suggest that the permeability of the blood—brain barrier may be affected by hydroxyl radicals and/or peroxynitrite rather than the O−2 itself. Copyright © 1996 Elsevier Science Ltd.

The phosphinated complexes RuCl 2 (PPh 3 ) 3 , 1 , RhCl(PPh 3 ) 3 , 2 , IrCl(CO)(PPh 3 ) 2 , 3 , their water soluble sulfonated analogs RuCl 2 [Ph 2 P(3-C 6 H 4 SO 3 Na)] 2 · 4H 2 O, 4 , RhCl[Ph 2 P(3-C 6 H 4 SO 3 Na)] 3 · 4H 2 O, 5 , IrCl(CO)[Ph 2 P(3-C 6 H 4 SO 3 Na)] 2 , 6 , as well as the dirhodium compounds trans -[Rh(CO)(PPh 3 )(μ-pz)] 2 , 7 , and trans -[Rh(CO)(PPh 3 )(μ-Cl)] 2 , 9 were entrapped physically in SiO 2 sol-gel matrices. Replacement of the PPh 3 ligands in the two latter complexes by Ph 2 P(CH 2 ) 2 Si(OEt) 3 groups enabled to bind of the dirhodium complexes chemically to the matrix backbone via the silyloxy functions. The activity of the immobilized complexes as allylbenzene isomerization catalysts was studied and compared. Entrapped complex 4 was found to be most efficient catalyst.

The water-soluble phosphine complex of Rh(I), RhCl(PTA) 3 ( 1 ) was shown to be an active catalyst for the hydrogenation of various olefinic and oxo-acids, as well as of allyl alcohol and 4-sulfostyrene in aqueous solution under mild conditions. Detailed kinetic investigations were carried out with crotonic acid and allyl alcohol as substrates. The rate of hydrogenation of both compounds showed a sharp maximum as a function of pH at 4.7. Hydrogenation of itaconic, crotonic and α-acetamidocinnamic acid in D 2 O led to 45–100% deuteration of the products with 25–100% stereoselectivity towards the α-carbon atom. These results, together with those of pH-static hydrogenation of complex 1 , suggest that water strongly assists the dehydrochlorination of 1 to yield the catalytically active monohydrido species HRh(PTA) 3 ( 2 ). Nevertheless, depending on the substrate and the pH of the solution the dihydridic pathway may remain partially operative.

The cerebral endothelium represents an active interface between blood and central nervous system. The blood-brain barrier restricts the free passage of nutrients, hormones, drugs and cellular elements to the brain. Recent studies performed on freshly isolated cerebral microvessels and cultured endothelial cells of brain capillaries provided a better understanding of the properties and functions of cerebral endothelial cells. This review summarizes the main findings of the in vitro approach in the blood-brain barrier research, describes the common endothelial and unique cerebral features of the brain endothelium, and provides a short overview on how these blood-brain barrier characteristics can be induced in cerebral endothelial cells by the neighbouring cells.

Histochemical localization of two lectins, Ulex europaeus agglutinin-I (UEA-I) and Tetragonolobus purpureus (TPA), was studied in the olfactory bulb of adult rats. In contrast to TPA, UEA-I detected a fucosylated glycoprotein that is only present in the surface membranes of olfactory sensory cells including the whole course of their neurites up to the final arborization in glomeruli. Immunoblotting revealed that UEA-I binds specifically to a protein of 205 kDa, while TPA stains several other glycoproteins. Affinity chromatography with the use of a UEA-I column identified the 205 kDa protein as a glycoform of neural cell adhesion molecule (N-CAM), specific for the rat olfactory sensory nerves.

The water-soluble phosphine complex of Rh(I), [Rh(PTAH)(PTA)2Cl]Cl(1), has been synthesized from RhCl3 and 1,3,5,-triaza-7-phosphaadamantane (PTA) in 96% ethanol. This complex is an effective catalyst for the regioselective reduction of unsaturated aldehydes to saturated aldehydes. The rate of hydrogenation of trans-cinnamaldehyde with sodium formate as reductant was studied as a function of catalyst, substrate, and sodium formate concentration. The presence of an excess of PTA was found to inhibit hydrogenations completely. This reaction was also found to be partially inhibited by cyclo-octatetraene and Hg(0), leading to the conclusion that both heterogenous and homogenous mechanisms are operating. Recycling experiments show complex 1 to be quite robust, with minimal leaching into the organic phase in a biphasic system. The complex resulting from the addition of an excess of PTA to 1, [Rh(PTAH)3(PTA)Cl]Cl3 (2) has been prepared and structurally characterized by a single crystal X-ray diffraction study. 31P and 1H NMR, IR and UV-VIS spectroscopy and pH titrametric measurements were employed to study the reactivity of the various rhodium PTA complexes in aqueous solutions.

The present study demonstrates that histamine could be taken up by and released from endothelial cells of brain capillaries. Incubation of cultured endothelial cells, with low (0.01–0.50 μM) concentrations of [ 3 H]histamine, resulted in a rapid uptake of the amine. The uptake was saturable, Na + -dependent and yielded an apparent K m 0.3 ± 0.02 μ M and a V max 4.6 ± 0.04 pmol/mg protein per min. After a 10-min incubation in a histamine-free medium, about 65% of [ 3 H]histamine was released from the cells. Na + -deprivation and high K + , as well as the treatment of the cells with ouabain affected the release, resulting in significantly higher rates of the efflux. The ability of cerebral endothelial cells to take up histamine from both luminal and abluminal sides but to release it mainly luminally, may function as an important mechanism to protect the neural tissue from the harmful effects of this endogenous mediator of inflammation.

Platelet membrane fluidity (PMF) was measured with three different fluorescent probes, 1,6-diphenyl-1,3,5-hexatriene (DPH), 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH), 3-( p -phenyl-1,3,5-hexatrienyl)phenyl-proprionic acid (DPH-PA), which labeled different parts of the bilayer (the hydrophobic core and the positively and negatively charged regions, respectively) in Alzheimer's disease (AD) patients with and without a family history of dementia, and in a control group. In support of earlier findings in the literature, significantly increased PMF was found by the application of DPH in both groups with AD. The use of the fluorescence probe TMA-DPH, however, revealed no differences between the groups. In contrast, significant rigidification was observed with DPH-PA, but only in the AD group with a positive family history of dementia. The plasma malondialdehyde levels appeared to be similar in each group. Our findings are discussed in light of the controversies regarding the value of PMF measurements in AD.

The distributions of axons immunoreactive for [Leu]- or [Met]enkephalin and GABA were studied in the superior cervical ganglion of adult rats. The antigens were visualized separately and in combination with neuropeptide Y by the immunoperoxidase technique, using reaction end-products of different colors. Similarities and differences were found in the light-microscopic innervation patterns of enkephalin- and GABA-immunoreactive nerve fibers. Both fiber systems were heterogeneously distributed within the superior cervical ganglion, forming denser networks in its rostral part than elsewhere in the ganglion. The appearance of labeled nerve fibers differed in the two systems. Enkephalin-immunoreactive axons exhibited dotted profiles due to a strong immunoreaction in the axonal varicosities as compared with that in the intervaricose segments, whereas GABA-positive fibers were evenly labeled in both parts of the axons. The most marked difference between the innervation patterns from enkephalin- and GABA-immunoreactive axons was the presence of bundles of varicose axons in conjunction with the basket-like aggregation of enkephalin-immunoreactive nerve terminals. The possibility that enkephalins and GABA are co-localized in certain axons was excluded in double-labeling studies, silver intensification being used for the first antigen and the nickel-enhanced diaminobenzidine reaction for the second antigen. Different subsets of principal neurons were richly innervated in a basket-like manner by axons immunoreactive for enkephalins and GABA. Additionally, combined staining with antisera against either enkephalin and neuropeptide Y or GABA and neuropeptide Y revealed that both subsets of principal neurons richly innervated either by enkephalin-immunoreactive or by GABA-immunoreactive axons were devoid of neuropeptide Y immunoreactivity. Thus, the enkephalinergic and GABAergic axons have different subpopulations of neuropeptide Y-negative principal neurons as targets in the superior cervical ganglion. These results provide further evidence that sympathetic ganglion cells can be classified on the basis of their receiving input from different sources.

Ever since the discovery of Paul Ehrlich (1885 Das Sauerstoff-bedürfnis des Organismus: Hirschwald, Berlin) about the restricted material exchange, existing between the blood and the brain, the ultimate goal of subsequent studies has been mainly directed towards the elucidation of relative importance of different cellular compartments in the peculiar penetration barrier consisting the structural basis of the blood-brain barrier (BBB). It is now generally agreed that, in most vertebrates, the endothelial cells of the central nervous system (CNS) are responsible for the unique penetration barrier, which restricts the free passage of nutrients, hormones, immunologically relevant molecules and drugs to the brain. After an era of studying with endogenous or exogenous tracers the unique permeability properties of cerebral endothelial cells in vivo, the next generation, i.e. the in vitro blood-brain barrier model system was introduced in 1973. Recent advances in our knowledge of the BBB have in part been made by studying the properties and function of cerebral endothelial cells (CEC) with this in vitro approach. This review summarizes the results obtained on isolated brain microvessels in the second decade of its advent.