Nitrile-functionalized pyridinium ionic liquids: synthesis, characterization, and their application in carbon-carbon coupling reactions

A series of relatively low-cost ionic liquids, based on the N-butyronitrile pyridinium cation [C(3)CNpy](+), designed to improve catalyst retention, have been prepared and evaluated in Suzuki and Stille coupling reactions. Depending on the nature of the anion, these salts react with palladium chloride to form [C(3)CNpy](2)[PdCl(4)] when the anion is Cl(-) and complexes of the formula [PdCl(2)(C(3)CNpy)(2)][anion](2) when the anion is PF(6)(-), BF(4)(-), or N(SO(2)CF(3))(2)(-). The solid-state structures of [C(3)CNpy]Cl and [C(3)CNpy](2)[PdCl(4)] have been established by single-crystal X-ray diffraction. The catalytic activity of these palladium complexes following immobilization in both N-butylpyridinium and nitrile-functionalized ionic liquids has been evaluated in Suzuki and Stille coupling reactions. All of the palladium complexes show good catalytic activity, but recycling and reuse is considerably superior in the nitrile-functionalized ionic liquid. Inductive coupled plasma spectroscopy reveals that the presence of the coordinating nitrile moiety in the ionic liquid leads to a significant decrease in palladium leaching relative to simple N-alkylpyridinium ionic liquids. Palladium nanoparticles have been identified as the active catalyst in the Stille reaction and were characterized using transmission electron microscopy.     

Forensic identification of explosive oxidizers by electrospray ionization mass spectrometry

The mass spectrometry of a group of inorganic oxidizers was studied using the electrospray ionization technique. It was found that a series of cluster ions were predominant in both positive- and negative-ion mode, allowing for the characterization of the investigated oxidizers. The identity of the recorded cluster ions was further confirmed by using some isotopically labeled compounds and tandem mass spectrometry with collision-induced dissociation. The use of electrospray ionization mass spectrometry for positive identification of major oxidizer components in explosive formulations was demonstrated by three samples of forensic interest.     

Synthesis and Crystal Structure of Two One—dimensional Chain Copper Complexes [Cu（TTA）2（4,4‘’—azpy）] and [Cu（TTA）2（3,3‘’—azpy）

Two copper complexes [Cu(TTA)₂(4,4′‐azpy)] (1) and [Cu‐(TTA)₂(3,3′‐azpy)] (2) (HTTA = 1,1,1‐trifluoro‐3‐(2‐thenoyl)‐acetone, 4,4′‐azpy = 4,4′‐azobispyridine, 3,3′‐azpy = 3,3′‐azobispyridine) were synthesized and characterized. The crystal structures were determined by X‐ray diffraction analysis. The crystal 1 belongs to triclinic with space group P1 , a = 0.8515(2) nm, b = 0.9259(2) nm, c = 0.9468(2) nm, a = 66.126(9)°, β = 79.667(9)°, γ = 90.13(1)°, Z = 1, V = 0.6692(2) nm³, D_c = 3.425 g/cm³, γ = 2.113 mm^?1, F(000) = 694, R₁ = 0.0594, wR₂ = 0.1499. The crystal 2 belongs to monoclinic with space group P2₁/c, a = 1.0661(2) nm, b = 1.4296(3) ran, c = 1.0041(3) nm, β = 114.50(3)°, V = 1.3926(5) nm³, Z = 2, D_c = 1.646 g/ cm³, μ = 1.015 mm^?1, F(000) = 694, R₁, = 0.0535, wR₂ = 0.1113. In the crystals of complexes 1 and 2, the copper atoms have distorted octahedral symmetry. The two compounds possess very similar one‐dimensional linear chains linked through the rodlike 4,4′‐azpy ligands or 3,3′‐azpy ligands.     

An indium(III)–water chain based on an unusual acyclic water pentamer

An in situ reaction under hydro­thermal conditions leads to the formation of the title compound, diaqua­(pyridine‐2‐carboxyl­ato)­(pyridine‐2,6‐dicarboxyl­ato)indium(II) trihydrate, [In(C₆H₄NO₂)(C₇H₃NO₄)(H₂O)₂]·3H₂O, in which the central In^III atom is seven‐coordinated by one pyridine‐2,6‐di­carboxyl­ate ligand, one pyridine‐2‐carboxyl­ate ligand and two water mol­ecules in a penta­gonal–bipyramidal coordination environment. An indium(III)–water chain based on an unusual water pentamer is observed.     

Electrostatic recognition and induced fit in the kappa-PVIIA toxin binding to Shaker potassium channel

Brownian dynamics (BD) and molecular dynamics (MD) simulations and electrostatic calculations were performed to study the binding process of kappa-PVIIA to the Shaker potassium channel and the structure of the resulting complex. BD simulations, guided by electrostatic interactions, led to an initial alignment between the toxin and the channel protein. MD simulations were then carried out to allow for rearrangements from this initial structure. After approximately 4 ns, a critical "induced fit" process was observed to last for approximately 2 ns. In this process, the interface was reorganized, and side chains were moved so that favorable atomic contacts were formed or strengthened, while unfavorable contacts were eliminated. The final complex structure was stabilized through electrostatic interactions with the positively charged side chain of Lys7 of kappa-PVIIA deeply inserted into the channel pore and other hydrogen bonds and by hydrophobic interactions involving Phe9 and Phe23 of the toxin. The validity of the predicted structure for the complex was assessed by calculating the effects of mutating charged and polar residues of both the toxin and the channel protein, with the calculated effects correlating reasonably well with experimental data. The present study suggests a general binding mechanism, whereby proteins are pre-aligned in their diffusional encounter by long-range electrostatic attraction, and nanosecond-scale rearrangements within the initial complex then lead to a specifically bound complex.     

Utilization of hypervalent iodine in organic synthesis: A novel and facile two‐step protocol for the synthesis of new derivatives of 1H‐Imidazo[1,2‐b]pyrazole by the cyclocondensation involving α‐Tosyloxyacetophenones

A series of new 2‐aryl‐7‐cyano/ethoxycarbonyl‐6‐methylthio‐1H‐imidazo[1,2‐b]pyrazoles ( 5 ) have been synthesized in moderate to good yields, via a two‐step cyclocondensation procedure of 5‐amino‐4‐cyano/ethoxycarbonyl‐3‐methylthio‐1H‐pyrazole ( 1 ) and α‐bromoacetophenones ( 3 ) or α‐tosyloxyacetophenones ( 2 ), which were prepared by the reactions of acetophenones with [hydroxy(tosyloxy)iodo]benzene (HTIB). The intermediates, 5‐amino‐1‐(aroylmethyl)‐4‐ cyano/ethoxycarbonyl‐3‐methylthio‐1H‐pyrazoles ( 4 ), have been isolated, serving as evidence for the regioselectivity. When utilizing α‐tosyloxy‐acetophenones, the reactions were more eco‐friendly, the reaction time was significantly reduced and the synthetic procedure was more convenient and easier to manipulate. Surprisingly, using potassium carbonate to displace sodium carbonate in the synthesis of 4 , in the case of 1 (R? CN), two novel cyclocondensation products have been isolated and fully characterized, followed by the proposal of a plausible mechanism.     

DFT studies on the multi‐channel reaction of CH3S+NO2

The mechanisms for the reaction of CH₃S with NO₂ are investigated at the QCISD(T)/6‐311++G(d,p)//B3LYP/6‐311++G(d,p) on both single and triple potential energy surfaces (PESs). The geometries, vibrational frequencies, and zero‐point energy (ZPE) correction of all stationary points involved in the title reaction are calculated at the B3LYP/6‐311++G(d,p) level. More accurate energies are obtained at the QCISD(T)/6‐311++G(d,p). The results show that 5 intermediates and 14 transition states are found. The reaction is more predominant on the single PES, while it is negligible on the triple PES. Without any barrier height for the whole process, the main channel of the reaction is to form CH₃SONO and then dissociate to CH₃SO+NO. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

μ‐{N,N′‐Bis[2‐(dimethyl­amino)ethyl]oxamidato(2–)}‐1κ2O,O′:2κ4N,N′,N′′,N′′′‐bis­(4,4′‐dimethyl‐2,2′‐bipyridine‐1κ2N,N′)dinickel(II) bis­(perchlorate)

In the crystal structure of the title complex, [Ni₂(C₁₀H₂₀N₄O₂)(C₁₂H₁₂N₂)₂](ClO₄)₂ or [Ni(dmaeoxd)Ni(dmbp)₂](ClO₄)₂ {H₂dmaeoxd is N,N′‐bis­[2‐(dimethyl­amino)ethyl]oxamide and dmbp is 4,4′‐dimethyl‐2,2′‐bipyridine}, the deprotonated dmaeoxd²⁻ ligand is in a cis conformation and bridges two Ni^II atoms, one of which is located in a slightly distorted square‐planar environment, while the other is in an irregular octa­hedral environment. The cation is located on a twofold symmetry axis running through both Ni atoms. The dmaeoxd²⁻ ligands inter­act with each other via C—H⋯O hydrogen bonds and π–π inter­actions, which results in an extended chain along the c axis.     

3—Mercaptopropionic Acid Capped Gold Nanoclusters：Quantized Capacitance in Aquesous Media

3-Mercaptopropionic acid monolayer protected gold nanoclusters (MPA-MPCs) were synthesized and characterized by transmission electorn microscopy,UV-Vis spectroscopy,X-ray photoelectron spectroscopy and Fourler transform infrared spectroscopy.The exact value of quantized double-layer capacitance of MPCs in aqueous media was obtained by differential pulse voltammograms.     

2-十四烷基-DTPA及其钆(Ⅲ)螯合物的合成与表征(英)

Synthesis and characterization of the ligand, [2-tetradecyl-3,6,9-tris(carboxymethyl)-3,6,9-triazaundecan-1,11-dioic acid, H₅L] and its Gd(Ⅲ) chelate are described. Protonation constants for H₅L (lgK_i^H = 10.80, 8.40, 4.30, 2.80, 2.15) and the stability constant for GdL^2- (lgK_GdL^2-= 22.75) were determined by potentiometric titration and are similar with the related values of DTPA and Gd-DTPA respectively. The results obtained show that the basicity of the ligand and the stability constant of its Gd(Ⅲ) chelate are not obviously altered after introduction of a linear chain tetradecyl group at the terminal acetic acid residue of DTPA.