Iridium-phosphine ligand complexes as an alternative to rhodium-based catalysts for the efficient hydroformylation of propene.

Expensive rhodium (Rh)-based catalysts have been widely used for the hydroformylation of propene. To find a cheaper and effective alternative to these Rh-based catalysts, herein, a series of phosphine ligands were used to coordinate with iridium, and their catalytic reactivities for the hydroformylation of propene were systematically investigated in this study. The effects of different phosphine ligands, pressures, temperatures, and catalyst dosages on the hydroformylation of propene were investigated. Tripyridyl phosphine iridium Ir2(cod)2Cl2-P(3-py)3 (Ir(I)-L5) and its derivatives exhibit the highest catalytic reactivity. Surprisingly, the catalytic reactivity of Ir(I)-L5 is higher than that of Rh2(cod)2Cl2-P(3-py)3 (Rh(I)-L5). When the Ir(I)-L5 complex is used as the catalyst, reactions performed in a polar solvent gave higher turnover number (TON) values than those in a non-polar solvent. Up to a TON of 503 can be obtained. Different n-butyraldehyde/iso-butyraldehyde (n/i) ratios can be obtained by adjusting the phosphine ligands or the proportion of gas pressure. The catalyst showed good reusability in five recycling experiments. Furthermore, based on DFT theoretical calculations, a probable reaction mechanism was proposed. It is reliable that an Ir-based catalyst can be considered as a highly effective catalyst for the hydroformylation of propylene with CO.

Experimental and theoretical study on the cyclic(alkyl)(amino)carbene-copper catalyzed Friedel-Crafts reaction of N,N-dialkylanilines with styrenes.

The Friedel-Crafts reaction of alkalinous substrates is challenging because of the coordination between amines and traditional acid catalysts. Based on theoretical research, we designed a catalytic process for the Friedel-Crafts reactions of N,N-dialkylanilines in the presence of CAAC-CuCl [CAAC = cyclic(alkyl)(amino)carbene] and KB(C6F5)4. Experimental results show that the catalytic system is suitable for a series of N,N-dialkylanilines and styrenes with good to excellent yields of para-selectivity products. The results are comparable to those obtained in carbene-gold catalyzed processes.

Hydrogenation of CO2 to Formate with H2 : Transition Metal Free Catalyst Based on a Lewis Pair.

Hydrogenation of CO2 to formate with H2 in the absence of transition metal is a long-standing challenge in catalysis. The reactions between tris(pentafluorophenyl)borane (BCF) and K2 CO3 (or KHCO3 ) are found to form a Lewis pair (K2 [(BCF)2 -CO3 ]) which can react with both H2 and CO2 to produce formate. Based on these stoichiometric reactions, the first catalytic hydrogenation process of CO2 to formate using transition metal free catalyst (BCF/M2 CO3 , M=Na, K, and Cs) is reported. The highest TON value of this catalytic process is up to 3941. Further research revealed the reaction mechanism in which the Lewis pair enables the splitting of H2 and the insertion of CO2 into the B-H bond.

[The Sun Glint Area Reflectance Calculation of VIIRS Middle Infrared Channel in South Indian Ocean Based on Improved Nonlinear Split Window Model].

The energy received through remote sensing sensors contains the amount of reflected solar energy and emitted energy of objects in middle-wave infrared (MWIR, 3~5 µm). Usually, the reflected solar energy is weak in MWIR spectrum. In some certain situations like sun glint area in sea surface, however, the energy is relatively significant and less sensitive to atmospheric effects. Meanwhile, for the satellite sensor which equipped with onboard calibration system, its onboard radiation performance of MWIR(using blackbody calibration)is quite stable. Therefore, the MWIR reflectance in sea surface glint area can be considered as a reference for cross-calibration between the solar reflected bands. Based on this idea, this paper constructed an improved non-linear split window model that is suitable for VIIRS (visible infrared imaging radiometer) MWIR band and used this model to calculate the MWIR reflectance of sun glint area in southern Indian Ocean. This model made statistics, getting the relationship between the reflectance of VIIRS M12 and M13 bands at first, and then used the non-linear split window algorithm to calculate the actual sea surface reflectance. The uncertainty of the simulation model was 0.83%. On this basis, this paper calculated sea surface reflectance of selected sample regions based on the data of VIIRS M12 band (center wavelength: 3.697 µm) in sun glint areas. And then verified the reflectance accuracy by two methods, getting the two accuracies were about 0.239% and 0.23%, respectively. It proves that the calculation model in this paper can greatly improve the accuracy compared to the situation when the sea surface reflectance is between M12 and M13 which are assumed to be equal (accuracy of 2.48% and 1.03%, respectively). It also indicated that the model is feasible and effective to calculate the reflectance in sea surface glint area with VIIRS M12 MWIR band, and the accuracy can meet the requirements of MWIR sea surface reflectance as a calibration reference among bands.

Air-Stable (CAAC)CuCl and (CAAC)CuBH4 Complexes as Catalysts for the Hydrolytic Dehydrogenation of BH3NH3.

The first stable copper borohydride complex [(CAAC)CuBH4] [CAAC = cyclic(alkyl)(amino)carbene] bearing a single monodentate ligand was prepared by addition of NaBH4 or BH3NH3 to the corresponding [(CAAC)CuCl] complex. Both complexes are air-stable and promote the catalytic hydrolytic dehydrogenation of ammonia borane. The amount of hydrogen released reaches 2.8 H2/BH3 NH3 with a turnover frequency of 8400 mol H2 molcat(-1) h(-1) at 25 °C. In a fifteen-cycle experiment, the catalyst was reused without any loss of efficiency.

Gold-catalyzed hydroarylation of alkenes with dialkylanilines.

Anti-Bredt di(amino)carbene supported gold(I) chloride complexes are readily prepared in two steps from the corresponding isocyanide complexes. In the presence of KB(C6F5)4 as chloride scavenger, they promote the unprecedented hydroarylation reaction of alkenes with N,N-dialkylanilines with high para-selectivity. The latter are challenging arenes for Friedel-Craft reactions, due to their high basicity.

Mechanism of lncRNA SNHG16 on kidney clear cell carcinoma cells by targeting miR-506-3p/ETS1/RAS/ERK molecular axis.

Objective: This study aimed to investigate the mechanism of long noncoding ribonucleic acid (lncRNA) SNHG16 on kidney clear cell carcinoma (KIRC) cells by targeting miR-506-3p/ETS proto-oncogene 1, transcription factor (ETS1)/RAS/Extracellular regulated protein kinases (ERK) molecular axis, thus to provide reference for clinical diagnosis and treatment of KIRC in the future. Methods: Thirty-six patients with KIRC were enrolled in this study, and their carcinoma tissues and adjacent tissues were obtained for the detection of SNHG16/miR-506-3p/ETS1/RAS/ERK expression. Then, over-expressed SNHG16 plasmid and silenced plasmid were transfected into KIRC cells to observe the changes of their biological behavior. Results: SNHG16 and ETS1 were highly expressed while miR-506- 3p was low expressed in KIRC tissues; the RAS/ERK signaling pathway was significantly activated in KIRC tissues (P < 0.05). After SNHG16 silence, KIRC cells showed decreased proliferation, invasion and migration capabilities and increased apoptosis rate; correspondingly, increase in SNHG16 expression achieved opposite results (P < 0.05). Finally, in the rescue experiment, the effects of elevated SNHG16 on KIRC cells were reversed by simultaneous increase in miR-506-3p, and the effects of miR-506-3p were reversed by ETS1. Activation of the RAS/ERK pathway had the same effect as increase in ETS1, which further worsened the malignancy of KIRC. After miR-506-3p increase and ETS1 silence, the RAS/ERK signaling pathway was inhibited (P < 0.05). At last, the rescue experiment (co-transfection) confirmed that the effect of SNHG16 on KIRC cells is achieved via the miR-506-3p/ETS1/RAS/ERK molecular axis. Conclusion: SNHG16 regulates the biological behavior of KIRC cells by targeting the miR-506-3p/ETS1/RAS/ERK molecular axis.

Deep eutectic solvent-based blended membranes for ultra-super selective separation of SO2.

SO2 is a major atmospheric pollutant leading to acid rain and smog. As a new generation of green solvents, deep eutectic solvents (DESs) have been widely investigated for gas capture. Nevertheless, studies on DES-based membranes for SO2 separation are yet minimal. Herein, we devised polymer/DES blended membranes comprising 1-butyl-3-methyl-imidazolium bromide ([Bmim]Br)/diethylene glycol (DEG) DES and poly (vinylidene fluoride) (PVDF), and these membranes were firstly used for selective separation of SO2 from N2 and CO2. The permeability of SO2 reaches up to 17480 Barrer (0.20 bar, 40 ºC) in PVDF/DES blended membrane containing 50 wt% of [Bmim]Br/DEG (2:1), with ultrahigh SO2/N2 and SO2/CO2 selectivity of 3690 and 211 obtained, respectively, far exceeding those in the state-of-the-art membranes reported in literature. The highly-reversible multi-site interaction between SO2 and [Bmim]Br/DEG DES was revealed by spectroscopic analysis. Furthermore, the PVDF/DES blended membrane was also able to efficiently and stably separate SO2/CO2/N2 (2.5/15/82.5%) mixed gas for at least 100 h. This work demonstrates for the first time that [Bmim]Br-based DESs are very efficient media for membrane separation of SO2. The easy preparation, low cost and high performance enable polymer/DES blended membranes to be promising candidates for flue gas desulfurization.

Reaction and separation system for CO2 hydrogenation to formic acid catalyzed by iridium immobilized on solid phosphines under base-free condition.

Hydrogenation of carbon dioxide (CO2) to produce formic acid (HCOOH) in base-free condition can avoid waste producing and simplify product separation process. However, it remains a big challenge because of the unfavorable energy in both thermodynamics and dynamics. Herein, we report the selective and efficient hydrogenation of CO2 to HCOOH under neutral conditions with imidazolium chloride ionic liquid as the solvent, catalyzed by a heterogeneous Ir/PPh3 compound. The heterogeneous catalyst is more effective than the homogeneous one because it is inert in catalyzing the decomposition of product. A turnover number (TON) of 12700 can be achieved, and HCOOH with a purity of 99.5% can be isolated by distillation because of the non-volatility of the solvent. Both the catalyst and imidazolium chloride can be recycled at least 5 times with stable reactivity.

Study on the alkylation of aromatic hydrocarbons and propylene.

In order to improve the efficiency of the alkylation reaction to aromatic hydrocarbons and propylene, different types of catalysts were screened, including ultra-stable Y molecular sieves (USY), solid phosphoric acid (SPA), ZSM type molecular sieve (HZSM), etc. The effects of reaction temperature, catalyst loading, and reaction time on the conversion rate of aromatic hydrocarbons and the selectivity of target products were investigated using the high-pressure reaction device. The catalysts were characterized by XRD, BET, SEM, FT-IR, NH3-TPD, and other methods. The experimental results show that the USY catalyst exhibits higher catalytic activity for alkylation. This catalyst can be used for the alkylation of different aromatic hydrocarbons. Good conversion and selectivity can be obtained. Futhermore, in a six-cycle experiment, the USY catalyst was reused without loss of efficiency.

Aerobic oxidation of aldehydes to acids in water with cyclic (alkyl)(amino)carbene copper under mild conditions.

In this work, cyclic (alkyl)(amino)carbene copper ((CAAC)Cu) catalyzed aerobic oxidation of aldehydes in water at room temperature has been reported. Good to excellent yields were obtained using different substrates. A possible reaction mechanism was proposed, in which (CAAC)Cu dioxygen activates the C-H bond of aldehyde with a low barrier of 10.6 kcal mol-1.

Ionic Liquids Endowed with Novel Hybrid Anions for Supercapacitors.

The synthesis of a novel class of ionic liquids (ILs) with sulfimide-type anions is presented herein. [Py14][PTSNTF] (N-butyl-N-methylpyrrolidinium p-tosyl(trifluoromethyl)sulfonimide) shows that the maximal electrochemical window is as high as 5.3 V, higher than that of most reported ILs. In addition, thermogravimetry analysis, differential scanning calorimetry, and the flammability test were also carried out for its thermal stability and practical safety. Impressively, these ILs exhibited good flame resistance and demonstrated an admirable intrinsic safety, in sharp contrast to ordinary electrolytes. Furthermore, the electrostatic potential of ILs was calculated theoretically, and the distribution of surrounding charge is intuitively understood. Cyclic voltammetry, galvanostatic charge-discharge tests, and cycling stability measurement were performed to evaluate the potential as the electrolyte for supercapacitors. The insights obtained from the study of novel anions provide new ideas for the design of novel IL electrolytes for energy applications.

Approaching and bond breaking energies in the C-H activation and their application in catalyst design.

It was found that the C-H activation barrier can be divided into two parts: C-H approaching and bond breaking energies. The C-H approaching process starts from the reactant and ends at a cross-point structure which is followed by the C-H breaking process. This finding was proved by the intrinsic reaction coordinate (IRC) analysis, vibration frequency (VF) analysis, atom-centered density matrix propagation (ADMP) calculation, and potential energy surface (PES) scan. Further research revealed that the C-H bond breaking energy was related to the electronic structure of the catalyst and the C-H bond dissociation energy of the substrate, whereas the C-H approaching energy was highly relative with the interaction between the substrate and catalyst. These results may be helpful in designing a more effective catalyst.

Reductive amination of ketones/aldehydes with amines using BH3N(C2H5)3 as a reductant.

Herein, we report the first example of efficient reductive amination of ketones/aldehydes with amines using BH3N(C2H5)3 as a catalyst and a reductant under mild conditions, affording various tertiary and secondary amines in excellent yields. A mechanistic study indicates that BH3N(C2H5)3 plays a dual function role of promoting imine and iminium formation and serving as a reductant in reductive amination.

Controlling the Lewis Acidity and Polymerizing Effectively Prevent Frustrated Lewis Pairs from Deactivation in the Hydrogenation of Terminal Alkynes.

Two strategies were reported to prevent the deactivation of Frustrated Lewis pairs (FLPs) in the hydrogenation of terminal alkynes: reducing the Lewis acidity and polymerizing the Lewis acid. A polymeric Lewis acid (P-BPh3) with high stability was designed and synthesized. Excellent conversion (up to 99%) and selectivity can be achieved in the hydrogenation of terminal alkynes catalyzed by P-BPh3. This catalytic system works quite well for different substrates. In addition, the P-BPh3 can be easily recycled.

B(C6 F5 )3 -Catalyzed Tandem Friedel-Crafts and C-H/C-O Coupling Reactions of Dialkylanilines.

Tandem Friedel-Crafts (FC) and C-H/C-O coupling reactions catalyzed by tris(pentafluorophenyl) borane (B(C6 F5 )3 ) were achieved without using any other additive in the absence of solvent. This process can be used for the reactions between a series of dialkylanilines and vinyl ethers with good isolated yields of bis(4-dialkylaminophenyl) compounds. Based on combined theoretical and experimental studies, the possible reaction mechanism was proposed. B(C6 F5 )3 can activate the C=C and C-O bond for FC and C-H/C-O coupling reactions respectively. The FC reaction is slow, which is followed by a fast C-H/C-O coupling.

Self-enhancement of CO reversible absorption accompanied by phase transition in protic chlorocuprate ionic liquids for effective CO separation from N2.

An efficient strategy for the high-capacity capture of CO is reported, and a phase change in protic chlorocuprate ionic liquids (PCILs) from liquid to solid is found during CO absorption. The highest CO capacity is 0.96 molCO molIL-1, being at least 150 times higher than that in [BMIM][PF6]. Both absorption and membrane permeation reveal that the PCILs are potential for the selective separation of CO from N2.

Why 1-NH and 3-NH protons of D-biotin exhibit different activities in aqueous solution.

Quantum chemical calculations, combined with the molecular dynamics results, have been employed to explain why the 1- and 3-NH protons of biotin exhibit different activities in aqueous solution. They suggested that the relative proportion of the three different conformations of biotin in the solution was responsible for different activities of the two amide protons of biotin. The relative activity of the two amide protons calculated by theoretical work here is 6, which is in good agreement with the experimental data, which is 5, reinforcing the viewpoint that biotin jumps between the three conformations in aqueous solution and the relative proportion of extended, semifolded, and folded biotin in water is 24:3.6:1. The method for computing the relative activity of the two amide protons of biotin in water here may be used to predict the relative activity in other solutions. The behavior of biotin in aqueous solution may be helpful for better understanding the unusual strong biotin-(strept)avidin binding.

Two unexpected roles of water: assisting and preventing functions in the oxidation of methane and methanol catalyzed by porphyrin-Fe and porphyrin-SH-Fe.

The C-H activation of methane and the O-H activation of methanol catalyzed by porphyrin-Fe and porphyrin-SH-Fe with water molecules in the microenvironment were investigated. It was found that there were two absolutely opposite regions in the vicinity of porphyrin-Fe. In one region (W1), water molecule can prevent the reaction, whereas in the other region (W2), water molecule can assist the reaction. The roles of W1 and W2 are unexpected compared with those reported in previous papers. Furthermore, the previous experimental phenomena can be explained by these results to some extent. These results are useful for understanding the influences of water on the oxidations with homogeneous catalysts and controlling the reactions by changing the microenvironment of the catalysts.

Friedel-Crafts Reaction of N,N-Dimethylaniline with Alkenes Catalyzed by Cyclic Diaminocarbene-Gold(I) Complex.

In general, Friedel-Crafts reaction is incompatible with amines due to the Lewis acidity of the catalysts. Recently, we reported that cyclic diaminocarbene-Gold(I) can be used as catalyst for the Friedel-Crafts alkylation between aromatic amines and alkenes. Herein, a systematically theoretical research was performed on this rare Friedel-Crafts reaction. The adopted calculation method is accurate enough to reproduce the crystal structure of the catalyst. It was found that the reactions followed the electrophilic aromatic substitution mechanism. The gold cation can activate the C=C double bond and generate the electrophilic group which can be attacked by the aromatic ring. The para-product is more energy favorable which agrees well with the experimental results. The reaction of α-methylstyrene follows the Markovnikov rule, and the activation energy to generate the branched product of methylstyrene is lower than that producing the linear product. However, the reaction of butanone follows the anti-Markovnikov rule, and the activation energy to generate the branched product of butanone is higher than that producing the linear product. These calculation results reveal the mechanism of this new Friedel-Crafts reaction. It can well explain the high para-selectivity and the substrate-dependent of the product structures in the experiment.