Solvent Effects on the Absorption Spectrum of the Product and the Equilibrium Constant for the Proton Transfer Reaction from 1-Phenacylquinolinium Bromide to Amines

The equilibrium constants, K ₂, have been determined for the proton-transfer reactions of 1-phenacylquinolinium ion, PHQ⁺, with several amines {triethylamine (TEA), N,N,N′,N′-tetramethylethylenediamine (ED), N,N,N′, N′-tetramethylpropanediamine (PD), N,N,N′,N′-tetramethylbutanediamine (BD), and 1,8-bis(dimethylamino-naphthalene (DMAN)} in acetonitrile (AN), AN-tetrahydrofuran (THF) and AN-ethanol (EtOH) mixtures. The reaction was followed spectrophotometrically using a stopped-flow technique. The K ₂ value decreased for DMAN and increased for TEA with increasing vol-% of THF in AN-THF mixtures. The changes in the K ₂ value for ED, PD and BD changed in the order: ED, PD and BD from a pattern similar to TEA to a pattern similar to DMAN. The change in the K ₂ value for DMAN with increasing vol-% of THF in AN-THF mixtures was explained by the effect of polarity on the stability of P⁻Q⁺ (the deprotonated product of PHQ⁺). The effect of THF on the K ₂ value is consistent with that of the peak wavelength of the absorption spectrum of P⁻Q⁺. The change in the K ₂ value for TEA, ED, PD and BD depended on the structures of the protonated bases, one of the products for this reaction. The effect of EtOH on the K ₂ value for DMAN was examined in ternary EtOH-THF-AN mixtures that contain different amounts of EtOH and whose relative permittivities were adjusted to that of EtOH. The K ₂ value increased with increasing vol-% of EtOH because of the stabilization of P⁻Q⁺ upon the formation of the hydrogen-bonded complex with EtOH. The absorption spectrum of P⁻Q⁺ demonstrated a blue shift as the vol-% of EtOH increased.     

Theoretical study on intermolecular interactions in BrF/HnX adducts

Equilibrium geometries, interaction energies, and charge transfer for the intermolecular interactions between BrF and H_nX (HF, H₂O, and NH₃) were studied at the MP2/6-311++G(3d,3p) level. The halogen-bonded geometry and hydrogen-bonded geometry are observed in these interactions. The calculated interaction energies show that the halogen-bonded structures are more stable than the corresponding hydrogen-bonded structures. To study the nature of the intermolecular interactions, symmetry-adapted perturbation theory (SAPT) calculations were carried out and the results indicate that the halogen bonding interactions are dominantly inductive energy in nature, while electrostatic energy governs the hydrogen bonding interactions.     

Visual recognition of melamine in milk via selective metallo-hydrogel formation

A novel protocol allowing convenient and highly selective visual recognition of melamine in raw milk via selective metallo-hydrogel formation at a concentration as low as 10 ppm without any tedious pretreatment has been developed.     

Fabrication of three-component hydrogen-bonded covalent-organic polymers for ciprofloxacin decontamination from water: adsorption mechanism and modeling

A three-component hydrogen-bonded covalent organic polymer, namely JLUE-H_COP-66, was fabricated via a facile multiple-linking-site solvothermal approach to overcome the weakness of poor function complexity and limited structure diversity of the pure covalent skeletons. The as-prepared JLUE-H_COP-66 polymers were employed to decontaminate ciprofloxacin (CIP), a popular F-quinolones (FQNs) antibiotic, from water and exhibited satisfactory adsorption performance. Specifically, JLUE-H_COP-66 polymers have high adsorption capacity with the maximum contribution of 111.1 mg/g according to the Langmuir model, good antiinterference to NaCl salts, and excellent regeneration property. The pH-dependent experiment results signified the probably dominated mechanism of electrostatic interaction. In addition, adsorption studies and structural characterization in combination illustrated that the pore-filling effect, hydrogen bonding formation might also govern the whole process, accompanied by electrostatic interaction, dipole-dipole complexation, π-π EDA interaction, and hydrophobic-hydrophobic interaction besides. Moreover, electrostatic potentials, as well as the frontier molecular orbital distributions (HOMO and LUMO) of CIP and JLUE-H_COP-66 fragment, were calculated using density functional theory to theoretically support the research. Furthermore, the response surface methodology (RSM) according to the CCD matrix was used to not only study the interactive and cooperative effects of initial CIP concentration, initial pH, ionic strength along with JLUE-H_COP-66 dosage on CIP removal using JLUE-H_COP-66 but also optimize the operation conditions. Given the peculiar structure and functional feature, this work could hopefully bring H_COPs into the practical applications of such challenging and persistent ciprofloxacin potent removal with further large-scale efficiency.     

基于含锌有机配位聚合物的微孔碳的合成及其电化学性能

报道了一种基于含锌(II)有机配位聚合物制备微孔碳的新方法. 通过锌离子和酒石酸之间的配位作用获得含锌有机配位化合物, 并通过氢键作用将其引入到间苯二酚/甲醛低聚物溶胶的开放网络结构中. 使含锌有机配位化合物和酚醛低聚物溶胶体系发生共聚反应得到酚醛和含锌有机配位共聚物, 在950℃下热处理分解以及锌蒸气蒸发后制得微孔碳. 微孔碳材料典型样品具有相对较大以及比较规则的微孔, 其比表面积可以达到1260 m²·g^-1, 孔体积为0.63 cm³·g^-1. 所得微孔碳作为超级电容器电极材料的等效串联电阻为0.46 Ω, 其循环伏安曲线展示出较好的矩形性. 恒流充放电分析结果表明, 当电流密度为1 A·g^-1时, 微孔碳电极的比电容为196 F·g^-1; 在10 A·g^-1的大电流密度下, 比电容仍然达到137 F·g^-1. 该电极具有优良的循环稳定性, 1000次循环后比电容保持率达到98%. 这一研究结果表明, 所得微孔碳在超级电容器电极材料方面具有重要的应用前景.     

Conformational change in a urea catalyst induced by sodium cation and its effect on enantioselectivity of a Friedel-Crafts reaction

While developing bis-camphorsulfonyl urea as a hydrogen-bonding catalysts, we discovered that the native conformation of the catalyst is unsuitable for inducing enantioselectivity. By complexing the catalyst with weakly Lewis acidic sodium cations, we were able to change the conformation of the catalyst and attain a significant improvement in the selectivity. We provide structural information from X-ray crystallography to show that the uncomplexed catalyst is indeed in an unfavorable conformation. Infrared and Raman spectroscopic studies show that sodium binds the catalyst through the carbonyl and sulfonyl groups. Simulated IR and Raman spectra match well with the experimentally recorded spectra, thereby corroborating the proposed conformational change. This result shows that weak Lewis acids can be used to tune the conformation of hydrogen-bonding catalysts and enhance the selectivity of reaction catalyzed by these systems.     

Ibuprofen induced drug loaded polymeric micelles

Three model drugs with different function groups were chosen to dialyze with dextran-graft-poly(N-isopropylacrylamide).Only ibuprofen could induce the formation of drug loaded micelles,which was confirmed with dynamic light scattering and transmission electron microscope.Hydrogen-bonding between the amide groups of poly(N-isopropylacrylamide) and the carboxyl groups of ibuprofen was driving force for the drug-loaded micelle.It was also found that the diameter of the ibuprofen-loaded micelles changed reversibly against temperature.     

ADSORPTION OF CAFFEINE BY HYDROGEN DONATING ADSORBENTS BASED ON HYDROGEN BONDING

1. INTRODUCTIONHydrogen bonding is a useful mechanism for adsorptive separation. The low enemy of thisbond ensures reversibility, while the directionality and the short range of this bond conferselectivity. The adsorption of hydrogen donating solutes onto an adsorbent capable of acceptinghydrogenedmberlite XAD-7, an adsorbent consisted of polycarboxylic ester--based onhydrogen bonding has been examined in detail 11-41. However, the adsorption of hydrogenaccepting solutes onto polymeric a…     

Reflection absorption infrared study of the adsorption of dimethylamine on copper (1 1 0) and nickel (1 1 1) surfaces

The adsorption of dimethylamine on Cu(1 1 0) and Ni(1 1 1) has been studied by reflection absorption infrared spectroscopy. For Cu(1 1 0), adsorption was molecular at 80 and 300 K and for submonolayer dimethylamine the appearance of A′ and not A″ modes indicated C_s symmetry. Similar bonding was found for Ni(1 1 1) at 170 K. Annealing the adlayer to 350 K resulted in the formation of a new species on Ni(1 1 1), similar to that which has been identified as methylaminocarbyne on Pt(1 1 1). In contrast only molecular dimethylamine was identified on Cu(1 1 0), with H-bonded interactions at high coverage and a potential surface dimer.     

Molecular receptors for monosaccharides: di(pyridyl)naphthyridine and di(quinolyl)naphthyridine

The recognition capabilities of two molecular receptors 2,7-di(3′-pyridyl)-1,8-naphthyridine (DPN) and 2,7-di(3′-quinolyl)-1,8-naphthyridine (DQN) toward monosaccharides in chloroform were evaluated. Both DPN and DQN possess a naphthyridine core moiety, in which two pyridinic nitrogen atoms serve as the proton acceptors. Attached to the C2 and C7 positions of naphthyridine are two identical arms, each of which consists of pyridine (DPN) or quinoline (DQN) moiety that also acts as the proton acceptor. The arrangement of hydroxyl groups in monosaccharides offers the proton donors complementary to the proton acceptors of DPN (or DQN) to form a quadruply hydrogen bonds complex. The binding processes were studied by UV-vis, fluorescence and ¹H NMR spectrophotometric titrations as well as electrospray ionization mass spectroscopy. The binding strength between DPN (or DQN) and examined monosaccharides was comparable to that for many other hydrogen-bonding host molecules previously reported.