Study on the photodegradation and microbiological degradation of pirimicarb insecticide by using liquid chromatography coupled with ion-trap mass spectrometry

The intermediates of photodegradation and microbial degradation of pirimicarb insecticide were investigated by liquid chromatography coupled with ion-trap mass spectrometry (LC–IT-MS). Different intermediates were detected in the photodegradation and microbial degradation of pirimicarb. In the photodegradation of pirimicarb in aqueous solution 2-dimethylamino-5,6-dimethyl-4-hydroxypyrimidine (MW = 167), 2-methylamino-5,6-dimethylpyrimidin-4-yl-dimethylcarbamate (MW = 224) and 2-formylamino-5,6-dimethylpyrimidin-4-yl-dimethylcarbamate (MW = 252) were the main products. It was found that 2-dimethylamino-5,6-dimethyl-4-hydroxypyrimidine (MW = 167) was the major product in the microbial degradation of pirimicarb in soil.     

Rationally designed 4-phenoxy substituted prolinamide phenols organocatalyst for the direct aldol reaction in water

A rationally designed 4-phenoxy substituted prolinamide phenols as an efficient hydrophobic organocatalyst for direct asymmetric aldol reaction in water has been developed. High yield (up to 99%), diastereoselectivity (up to 99:1), and enantioselectivity (up to 97%) were obtained under optimal condition. The influence of substituent groups on the reactivity of catalysts was studied in detail.     

First‐principles calculations of the stability and electronic properties of the PbTiO3 (110) polar surface

The structural and electronic properties of five terminations of cubic lead titanate (PbTiO₃) (110) polar surface were investigated by first‐principles total‐energy calculations using a periodic slab model. On the PbTiO termination, an anomalous filling of conduction band was observed, whereas on the O₂ termination, two surface oxygen atoms formed a peroxo group, demonstrating that the electronic structures of the two stoichiometric terminations undergo significant changes with respect to bulk materials. However, for the three nonstoichiometric TiO‐, Pb‐, and O‐terminated surfaces, their electronic structures are very similar to bulk. Charge redistribution results for the five terminations confirmed that electronic structure and surface composition changes are responsible for their polarity compensation. However, which mechanism actually dominates the stabilization process depends upon energetic considerations. A thermodynamic stability diagram suggested that the two stoichiometric terminations are unstable; however, the three nonstoichiometric terminations can be stabilized in some given regions. Furthermore, this study indicates that the very different stabilities and surface states filling behaviors of the PbTiO₃ (110) polar surface with respect to SrTiO₃ and BaTiO₃ ones seem to originate from the partially covalent characteristics of Pb O pairs. © 2008 Wiley Periodicals, Inc. J Comput Chem 2009     

Effect of surface chemistry on the adsorption of basic dyes on carbon aerogels

This paper focuses on how the surface chemical groups of carbon aerogels (CAs) affect their adsorption properties of basic dyes. First of all, the surface structures of CAs were tailored by controlling carbonization temperatures and oxidation treatments including HNO₃ oxidation, H₂O₂ oxidation and hot air oxidation. The pore structures of samples were investigated by N₂ adsorption–desorption analysis. In addition, their surface chemistries were characterized by Boehm titration, elemental analysis and XPS analysis. Subsequently, the adsorption capacities of the typical basic dyes on them were determined by UV Spectroscopy. The results show that the surface chemistry of CAs plays a key role in dye adsorption performance. HNO₃ oxidation can produce much acidic groups on the surface of sample, such as carboxyl, lactone and phenolic groups, resulting in an increase in the adsorption amounts of basic dyes.     

Novel designed polymer–acyclovir conjugates with linker‐controlled drug release and hepatoma cell targeting

To develop designed polymer–drug conjugates, where the rate of drug liberation and hepatoma cell targeting function could be rationally and widely controlled, we facilely synthesized a series of novel, galactose‐functionalized polymer–acyclovir conjugates with different linkers and first reported the effect of the linker structure including the type of acyclovir‐linked bond (an ester bond or an amide bond) and relative length of the linker between acyclovir and the polymer main chain on release rate and targeting ability of conjugates. In vitro release studies showed that the cumulative released acyclovir from these polymer–acyclovir conjugates was between 24 and 65% in pH 1.2 glycine solution after 7 days. The ester bond more easily underwent hydrolysis than the amide bond. The longer the relative linker length was, the faster the acyclovir was released. The cell recognition experiments visualized using confocal laser scanning microscopy exhibited that the resultant galactose‐functionalized polymer–acyclovir conjugates had evident targeting to hepG2 cells, and targeting ability was also in connection with the relative length of linker. By choosing appropriate linker, cellular internalization of acyclovir could be well achieved. We consider these results to be helpful for the design of multifunctional polymeric prodrugs, in which the required release rate and targeting ability could be rationally controlled by predetermined molecular architecture. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 117–126, 2008     

One‐pot synthesis of heterograft copolymers via “graft onto” by atom transfer nitroxide radical coupling chemistry

Heterograft copolymers poly(4‐glycidyloxy‐2,2,6,6‐tetramethylpiperidine‐1‐oxyl‐co‐ ethylene oxide)‐graft‐polystyrene and poly(tert‐butyl acrylate) (poly (GTEMPO‐co‐EO)‐g‐PS/PtBA) were synthesized in one‐pot by atom transfer nitroxide radical coupling (ATNRC) reaction via “graft onto.” The main chain was prepared by the anionic ring‐opening copolymerization of ethylene oxide (EO) and 4‐glycidyloxy‐2,2,6,6‐tetramethylpiperidine‐1‐oxyl (GTEMPO) first, then the polystyrene and poly (tert‐butyl acrylate) with bromine end (PS‐Br, PtBA‐Br) were prepared by atom transfer radical polymerization (ATRP). When three of them were mixed each other in the presence of CuBr/N,N,N′,N″,N″‐pentamethyldiethylenetriamine (PMDETA) at 90 °C, the formed secondary carbon radicals at the PS and PtBA chain ends were quickly trapped by nitroxide radicals on poly(GTEMPO‐co‐EO). The heterograft copolymers were well defined by ¹H NMR, size exclusion chromatography, fourier transform infrared, and differential scanning calorimetry in detail. It was found that the density of GTEMPO groups on main chain poly(GTEMPO‐co‐EO), the molecular weights of PS/PtBA side chains, and the structure of macroradicals can exert the great effects on the graft efficiency. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6770–6779, 2008     

A grid‐like two‐dimensional AgI coordination polymer: poly[[[μ3‐N′‐(4‐cyanobenzylidene)isonicotinohydrazide]silver(I)] perchlorate]

This study presents new coordinating modes of a Schiff base with three coordinating groups and an interesting two‐dimensional framework based on two types of constructing units. In the title compound, {[Ag(C₁₄H₁₀N₄O)]ClO₄}_n, the Ag^I ion is coordinated by three N atoms and one O atom from three different N′‐(4‐cyanobenzylidene)isonicotinohydrazide (L) ligands, forming a primary distorted square‐planar coordination geometry. Two ligands each bridge two metal centres through one carbonitrile N atom in a monodentate mode and the hydrazide N and O atoms in a bidentate mode to form a small centrosymmetric (2+2)‐Ag₂L₂ ring as a principal constructing unit. The pyridyl N atoms from four ligands in four of these small rings coordinate to Ag atoms in adjacent rings to form a large hexanuclear silver grid. A two‐dimensional framework of rectangular grids is constructed from these small rings and large grids. Two perchlorate anions are located in each large grid and are bound to the grid by N—H...O hydrogen bonding. Crosslinking between the layers is achieved through long Ag...O interactions between the perchlorate anions and Ag atoms in adjacent layers.     

A simple synthesis of 2,2′-bipyrroles from pyrrole

2,2′-Bipyrroles, which are obvious precursors for the synthesis of 2,2′-bipyrrole-based natural products, are synthesized in three steps from pyrrole employing known pyrrolyl ketoalcohols by a sequential alcohol oxidation and Paal-Knorr pyrrole synthesis.     

A Biomass-Ligand-Based Ru(III) Complex as a Catalyst for Cycloaddition of CO2 and Epoxides to Cyclic Carbonates and a Study of the Mechanism

Aiming highly efficient conversion of greenhouse gas CO₂ to cyclic carbonates, a biomass Ru(III) Schiff base complex catalyst ( SalRu ) was constructed by employing a derivative of Lignin degradation (5-aldehyde vanillin). The SalRu catalyst had a remarkable conversion for epoxides into corresponding cyclic carbonates even at atmospheric pressure of CO₂ without the presence of co-catalyst. As the condition at 120 °C and 2 MPa CO₂ the conversion reached to 94 % with selectivity at 99 % after 8 h. 32 % cyclic carbonate production was obtained even under 0.2 MPa CO₂ pressure. The epoxide activation and ring opening, CO₂ insertion and cyclic carbonate formation were illuminated explicitly through the of characteristic absorption peaks changing, which further providing direct and visual evidence for the mechanism proposing. This study has important theoretical significance for the comprehensive utilization of environmental pollutants and energy.