Hydrogenation of CO2 to formate catalyzed by a Ru catalyst supported on a copolymerized porous organic polymer.

The catalytic hydrogenation of carbon dioxide to formate is of great interest due to its significant role in CO2 utilization. In this study, a novel heterogeneous Ru(III) catalyst was prepared by immobilizing RuCl3 on a porous organic polymer (POP) obtained from 1,4-phthalaldehyde (PTA) and 4,4'-biphenyldicarboxaldehyde (BPDA) with melamine. A copolymerization strategy utilizing monomers of varying lengths was employed to prepare the POP-supported Ru catalyst with adjustable porosity. The optimization of the framework porosity resulted in enhanced CO2 affinity, accelerated mass transfer, and a remarkable enhancement in catalytic activity. A high turnover number (TON) of 2458 was achieved for the CO2 hydrogenation to formate in 2 h with catalyst Cat-3 under 3 MPa (CO2/H2 = 1 : 1) at 120 °C in 1 M Et3N aqueous solution. Moreover, the Cat-3 demonstrated good recyclability and was able to be reused for five consecutive runs, resulting in a high total TON of 9971.

An Ultrasound-Induced Self-Clearance Hydrogel for Male Reversible Contraception.

Nearly half of pregnancies worldwide are unintended mainly due to failure of contraception, resulting in negative effects on women's health. Male contraception techniques, primarily condoms and vasectomy, play a crucial role in birth control, but cannot be both highly effective and reversible at the same time. Herein, an ultrasound (US)-induced self-clearance hydrogel capable of real-time monitoring is utilized for in situ injection into the vas deferens, enabling effective contraception and noninvasive recanalization whenever needed. The hydrogel is composed of (i) sodium alginate (SA) conjugated with reactive oxygen species (ROS)-cleavable thioketal (SA-tK), (ii) titanium dioxide (TiO2), which can generate a specific level of ROS after US treatment, and (iii) calcium chloride (CaCl2), which triggers the formation of the hydrogel. For contraception, the above mixture agents are one-time injected into the vas deferens, which can transform from liquid to hydrogel within 160 s, thereby significantly physically blocking the vas deferens and inhibiting movability of sperm. When fertility is needed, a noninvasive remedial ultrasound can make TiO2 generate ROS, which cleaves SA-tK to destroy the network of the hydrogel. Owing to the recanalization, the refertility rate is restored to 100%. Meanwhile, diagnostic ultrasound (D-US, 22 MHz) can monitor the occlusion and recanalization process in real-time. In summary, the proposed hydrogel contraception can be a reliable, safe, and reversible male contraceptive strategy that addresses an unmet need for men to control their fertility.

Efficient Iridium Catalysts for Formic Acid Dehydrogenation: Investigating the Electronic Effect on the Elementary ß-Hydride Elimination and Hydrogen Formation Steps.

We report herein a series of Cp*Ir complexes containing a rigid 8-aminoquinolinesulfonamide moiety as highly efficient catalysts for the dehydrogenation of formic acid (FA). The complex [Cp*Ir(L)Cl] (HL = N-(quinolin-8-yl)benzenesulfonamide) displayed a high turnover frequency (TOF) of 2.97 × 104 h-1 and a good stability (>100 h) at 60 °C. Comparative studies of [Cp*Ir(L)Cl] with the rigid ligand and [Cp*Ir(L')Cl] (HL' = N-propylpypridine-2-sulfonamide) without the rigid aminoquinoline moiety demonstrated that the 8-aminoquinoline moiety could dramatically enhance the stability of the catalyst. The electron-donating ability of the N,N'-chelating ligand was tuned by functionalizing the phenyl group of the L ligand with OMe, Cl, and CF3 to have a systematical perturbation of the electronic structure of [Cp*Ir(L)Cl]. Experimental kinetic studies and density functional theory (DFT) calculations on this series of Cp*Ir complexes revealed that (i) the electron-donating groups enhance the hydrogen formation step while slowing down the ß-hydride elimination and (ii) the electron-withdrawing groups display the opposite effect on these reaction steps, which in turn leads to lower optimum pH for catalytic activity compared to the electron-donating groups.

Synergistic Effect of Pendant N Moieties for Proton Shuttling in the Dehydrogenation of Formic Acid Catalyzed by Biomimetic IrIII Complexes.

Formic acid (FA) is among the most promising hydrogen storage materials. The development of efficient catalysts for the dehydrogenation of FA via molecular-level control and precise tuning remains challenging. A series of biomimetic Ir complexes was developed for the efficient dehydrogenation of FA in an aqueous solution without base addition. A high turnover frequency of 46510 h-1 was achieved at 90 °C in 1 m FA solution with complex 1 bearing pendant pyridine. Experimental and mechanistic studies revealed that the integrated pendant pyridine and pyrazole moieties of complex 1 could act as proton relay and facilitate proton shuttling in the outer coordination sphere. This study provides a new strategy to control proton transfer accurately and a new principle for the design of efficient catalysts for FA dehydrogenation.

Ultrasmall Ni-ZnO/SiO2 Synergistic Catalyst for Highly Efficient Hydrogenation of NaHCO3 to Formic Acid.

Conversion of CO2 into fuels and chemicals has been considered to be an important strategy to reduce greenhouse gas emissions and alleviate the energy crisis. Bicarbonate as a CO2 source is convenient for experimental operation. Herein, based on the synergistic effect of Ni and ZnO benefitting from the electronic transfer, ultrasmall Ni-ZnO clusters (∼2 nm) stabilized by microporous silica nanoparticles were designed and prepared for catalyzing the hydrogenation of sodium bicarbonate to formic acid. The yield of formic acid reached up to 97.0% at 260 °C/3 MPa for 2 h, which is higher than those reported non-noble metal-based catalysts. The good performance of Ni-ZnO/SiO2 can be attributed to the ultrasmall active component size and the synergy effect based on electron transfer between Ni and ZnO.

Room temperature oxidative desulfurization with MoO3 subnanoclusters supported on MCM-41.

Subnano MoO3/MCM-41 was successfully prepared through doping (NH4)6Mo7O24 in the synthesis process of MCM-41. The morphology of MoO3/MCM-41 was visually observed by TEM and HADDF-STEM. N2 sorption, XPS and Raman were further applied to investigate the structure of the material. MoO3/MCM-41 was used in the oxidative desulfurization process with tert-butyl hydroperoxide as oxidant. MoO3/MCM-41 showed outstanding catalytic activity and recycling ability at room temperature.

CO2 Hydrogenation Catalyzed by Iridium Complexes with a Proton-Responsive Ligand.

The catalytic cycle for the production of formic acid by CO2 hydrogenation and the reverse reaction have received renewed attention because they are viewed as offering a viable scheme for hydrogen storage and release. In this Forum Article, CO2 hydrogenation catalyzed by iridium complexes bearing sophisticated N^N-bidentate ligands is reported. We describe how a ligand containing hydroxy groups as proton-responsive substituents enhances the catalytic performance by an electronic effect of the oxyanions and a pendent-base effect through secondary coordination sphere interactions. In particular, [(Cp*IrCl)2(TH2BPM)]Cl2 (Cp* = pentamethylcyclopentadienyl; TH2BPM = 4,4',6,6'-tetrahydroxy-2,2'-bipyrimidine) enormously promotes the catalytic hydrogenation of CO2 in basic water by these synergistic effects under atmospheric pressure and at room temperature. Additionally, newly designed complexes with azole-type ligands were applied to CO2 hydrogenation. The catalytic efficiencies of the azole-type complexes were much higher than that of the unsubstituted bipyridine complex [Cp*Ir(bpy)(OH2)]SO4. Furthermore, the introduction of one or more hydroxy groups into ligands such as 2-pyrazolyl-6-hydroxypyridine, 2-pyrazolyl-4,6-dihydroxypyrimidine, and 4-pyrazolyl-2,6-dihydroxypyrimidine enhanced the catalytic activity. It is clear that the incorporation of additional electron-donating functionalities into proton-responsive azole-type ligands is effective for promoting further enhanced hydrogenation of CO2.

Formic acid dehydrogenation with bioinspired iridium complexes: a kinetic isotope effect study and mechanistic insight.

Highly efficient hydrogen generation from dehydrogenation of formic acid is achieved by using bioinspired iridium complexes that have hydroxyl groups at the ortho positions of the bipyridine or bipyrimidine ligand (i.e., OH in the second coordination sphere of the metal center). In particular, [Ir(Cp*)(TH4BPM)(H2 O)]SO4 (TH4BPM: 2,2',6,6'-tetrahydroxyl-4,4'-bipyrimidine; Cp*: pentamethylcyclopentadienyl) has a high turnover frequency of 39 500 h(-1) at 80 °C in a 1 M aqueous solution of HCO2 H/HCO2 Na and produces hydrogen and carbon dioxide without carbon monoxide contamination. The deuterium kinetic isotope effect study clearly indicates a different rate-determining step for complexes with hydroxyl groups at different positions of the ligands. The rate-limiting step is ß-hydrogen elimination from the iridium-formate intermediate for complexes with hydroxyl groups at ortho positions, owing to a proton relay (i.e., pendent-base effect), which lowers the energy barrier of hydrogen generation. In contrast, the reaction of iridium hydride with a proton to liberate hydrogen is demonstrated to be the rate-determining step for complexes that do not have hydroxyl groups at the ortho positions.

Efficient water oxidation with organometallic iridium complexes as precatalysts.

Catalytic water oxidation has been investigated using five iridium complexes as precatalysts and NaIO4 as an oxidant at various pH conditions. An increase in the activity of all complexes was observed with increasing pH. A detailed analysis of spectroscopic data together with O2-evolution experiments using Cp*Ir(6,6'-dihydroxy-2,2'-bipyridine)(OH2)(2+) as a precatalyst indicate that the high catalytic activity is closely connected with transient species (A) that exhibits an absorption band at λmax 590 nm. The formation of this active form is strongly dependent on reaction conditions, and the species was distinctly observed using a small excess of periodate. However, another species absorbing at 600 nm (B), which seems to be a less active catalyst, was also observed and was more prominent at high oxidant concentration. Dynamic light scattering analysis and transmission electron microscopy have identified species B as 120 nm nanoparticles. The ultrafiltration method has revealed that species A can be attributed to particles with size in the range of 0.5­2 nm, possibly small IrOx clusters similar to those described previously by Harriman and co-workers (J. Phys. Chem., 1991, 95, 616­621).

Cp*Co(III) catalysts with proton-responsive ligands for carbon dioxide hydrogenation in aqueous media.

New water-soluble pentamethylcyclopentadienyl cobalt(III) complexes with proton-responsive 4,4'- and 6,6'-dihydroxy-2,2'-bipyridine (4DHBP and 6DHBP, respectively) ligands have been prepared and were characterized by X-ray crystallography, UV-vis and NMR spectroscopy, and mass spectrometry. These cobalt(III) complexes with proton-responsive ligands predominantly exist in their deprotonated [Cp*Co(DHBP-2H(+))(OH2)] forms with stronger electron-donating properties in neutral and basic solutions, and are active catalysts for CO2 hydrogenation in aqueous bicarbonate media at moderate temperature under a total 4-5 MPa (CO2:H2 1:1) pressure. The cobalt complexes containing 4DHBP ligands ([1-OH2](2+) and [1-Cl](+), where 1 = Cp*Co(4DHBP)) display better thermal stability and exhibit notable catalytic activity for CO2 hydrogenation to formate in contrast to the catalytically inactive nonsubstituted bpy analogues [3-OH2](2+) (3 = Cp*Co(bpy)). While the catalyst Cp*Ir(6DHBP)(OH2)(2+) in which the pendent oxyanion lowers the barrier for H2 heterolysis via proton transfer through a hydrogen-bonding network involving a water molecule is remarkably effective (ACS Catal. 2013, 3, 856-860), cobalt complexes containing 6DHBP ligands ([2-OH2](2+) and [2-Cl](+), 2 = Cp*Co(6DHBP)) exhibit lower TOF and TON for CO2 hydrogenation than those with 4DHBP. The low activity is attributed to thermal instability during the hydrogenation of CO2 as corroborated by DFT calculations.

Functionalized cyclopentadienyl rhodium(III) bipyridine complexes: synthesis, characterization, and catalytic application in hydrogenation of ketones.

A series of highly functionalized cyclopentadienyl rhodium(III) complexes, [Cp'Rh(bpy)Br](ClO4) (Cp' = substituted cyclopentadienyl), was synthesized from various multi-substituted cyclopentadienes (Cp'H). [Rh(cod)Cl]2 and Cp'H were firstly converted to [Cp'Rh(cod)] complexes, which were then treated with Br2 to give the rhodium(III) dibromides [Cp'RhBr2]2. The novel complexes [Cp'Rh(bpy)Br](ClO4) were obtained readily by the reaction of 2,2'-bipyridine with [Cp'RhBr2]2. These rhodium complexes [Cp'Rh(bpy)Br](ClO4) were fully characterized and utilized in the hydrogenation of cyclohexanone and acetophenone with generally high yields, but they did not exhibit the same reactivity trends for the two substrate ketones. The different activity of these complexes for the different substrates may be due to the influence of the substituents on the Cp' rings.

Highly efficient D2 generation by dehydrogenation of formic acid in D2O through H+/D+ exchange on an iridium catalyst: application to the synthesis of deuterated compounds by transfer deuterogenation.

Deuterated compounds have received increasing attention in both academia and industrial fields. However, preparations of these compounds are limited for both economic and practical reasons. Herein, convenient generation of deuterium gas (D(2)) and the preparation of deuterated compounds on a laboratory scale are demonstrated by using a half-sandwich iridium complex with 4,4'-dihydroxy-2,2'-bipyridine. The "umpolung" (i.e., reversal of polarity) of a hydrogen atom of water was achieved in consecutive reactions, that is, a cationic H(+)/D(+) exchange reaction and anionic hydride or deuteride transfer, under mild conditions. Selective D(2) evolution (purity up to 89 %) was achieved by using HCO(2)H as an electron source and D(2)O as a deuterium source; a rhodium analogue provided HD gas (98 %) under similar conditions. Furthermore, pressurized D(2) (98 %) without CO gas was generated by using DCO(2)D in D(2)O in a glass autoclave. Transfer deuterogenation of ketones gave α-deuterated alcohols with almost quantitative yields and high deuterium content by using HCO(2)H in D(2)O. Mechanistic studies show that the H(+)/D(+) exchange reaction in the iridium hydride complex was much faster than ß-elimination and hydride (deuteride) transfer.

Reversible hydrogen storage using CO2 and a proton-switchable iridium catalyst in aqueous media under mild temperatures and pressures.

Green plants convert CO(2) to sugar for energy storage via photosynthesis. We report a novel catalyst that uses CO(2) and hydrogen to store energy in formic acid. Using a homogeneous iridium catalyst with a proton-responsive ligand, we show the first reversible and recyclable hydrogen storage system that operates under mild conditions using CO(2), formate and formic acid. This system is energy-efficient and green because it operates near ambient conditions, uses water as a solvent, produces high-pressure CO-free hydrogen, and uses pH to control hydrogen production or consumption. The extraordinary and switchable catalytic activity is attributed to the multifunctional ligand, which acts as a proton-relay and strong π-donor, and is rationalized by theoretical and experimental studies.

4-Chloro-2-((1R)-1-{[(R)-(2-chloro-phen-yl)(cyclo-pent-yl)meth-yl]amino}eth-yl)phenol.

The title compound, C(20)H(23)Cl(2)NO, was prepared by condensation of (R)-1-(2-chloro-phen-yl)-1-cyclo-pentyl-methanamine with 1-(5-chloro-2-hydroxy-phen-yl)ethanone, resulting in the formation of a new chiral center. The structural analysis confirms the absolute configuration of the title compound and the formation of the (R,R) diastereoisomer. There is an intra-molecular O-H⋯N hydrogen bond which stabilizes the conformation of the mol-ecule. The mol-ecules are linked to each other through weak C-H⋯π inter-actions.

4-Chloro-2-((1R)-1-{[(R)-(2-chlorophen-yl)(cyclo-pent-yl)meth-yl]amino}prop-yl)phenol.

In the title compound, C(21)H(25)Cl(2)NO, the dihedral angle between the two benzene rings is 33.18 (11)°. The five-membered ring adopts an envelope conformation. There is an intra-molecular O-H⋯N hydrogen bond. In the crystal, mol-ecules are linked by weak N-H⋯Cl hydrogen bonds, forming a helical chain along the c axis.

4-Methyl-2-[(E)-phen-yl(1,2,3,4-tetra-hydro-1-naphthyl-imino)meth-yl]phenol.

In the crystal structure of the title compound, C(24)H(23)NO, the phenyl ring makes dihedral angles of 81.53 (11) and 75.35 (12)°, respectively, with the methyl-substituted and the fused benzene rings. The dihedral angle between the two benzene rings is 71.10 (10)°. There is an intra-molecular O-H⋯N hydrogen bond.

[Analysis of volatile components from the flowers of Chrysanthemum morifolium by GC-MS with solid-phase microextraction].

OBJECTIVE: To study a method for extraction and analysis of volatile components from Chrysanthemum morifolium 'gonghuangjv' cv. nov (CM GHJ) and C. morifolium 'gongbaijv' cv. nov (CM GBJ) by solid-phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS). METHOD: The volatile components were extracted in different temperature, different balance period and different extraction fiber using head space solid-phase microextraction (HS-SPME), and were identified by CGC-MS. The variety in integral area of each component was observed in different conditions and its relative content was determined by normalization of area. RESULT: The better condition of SPME for C. morifolium was that the sample was extracted using 100 microm polydimethylsiloxane (PDMS) extraction fiber after it had been balanced for 6 hours at 75 degrees C. 53 components from CM GHJ and CM GBJ were identified, and there were 35 same components in CM GHJ and CM GBJ. CONCLUSION: HS-SPME-GC-MS is convenient, rapid and reliable for analysis of volatile components in C. morifolium.