Influence of the water molecule on cation-pi interaction: ab initio second order Møller-Plesset perturbation theory (MP2) calculations

The influence of introducing water molecules into a cation-pi complex on the interaction between the cation and the pi system was investigated using the MP2/6-311++G method to explore how a cation-pi complex changes in terms of both its geometry and its binding strength during the hydration. The calculation on the methylammonium-benzene complex showed that the cation-pi interaction is weakened by introducing H(2)O molecules into the system. For example, the optimized interaction distance between the cation and the benzene becomes longer and longer, the transferred charge between them becomes less and less, and the cation-pi binding strength becomes weaker and weaker as the water molecule is introduced one by one. Furthermore, the introduction of the third water molecule leads to a dramatic change in both the complex geometry and the binding energy, resulting in the destruction of the cation-pi interaction. The decomposition on the binding energy shows that the influence is mostly brought out through the electrostatic and induction interactions. This study also demonstrated that the basis set superposition error, thermal energy, and zero-point vibrational energy are significant and needed to be corrected for accurately predicting the binding strength in a hydrated cation-pi complex at the MP2/6-311++G level. Therefore, the results are helpful to better understand the role of water molecules in some biological processes involving cation-pi interactions.     

Fluoro-substituted DPP-bisthiophene conjugated polymer with azides in the side chains as ambipolar semiconductor and photoresist

Photoresists are essential for the fabrication of flexible electronics through all-photolithographic processes. Single component semiconducting photoresist exhibits both semiconducting and photo-patterning properties, and as a result, the device fabrication process can be simplified. However, the design of semiconducting polymeric photoresist with ambipolar semiconducting property remains challenging. In this paper, we report a single component semiconducting photoresist (PFDPPF4T-N₃) by incorporating azide groups and noncovalent conformation locks into the side alkyl chains and conjugated backbones of a diketopyrrolopyrrole-based conjugated polymer, respectively. The results reveal that PFDPP4FT-N₃ exhibits ambipolar semiconducting property with hole and electron mobilities up to 1.12 and 1.17 cm² V^?1 s^?1, respectively. Moreover, field effect transistors with the individual photo-patterned thin films of PFDPPF4T-N₃ also show ambipolar semiconducting behavior with hole and electron mobilities up to 0.66 and 0.80 cm² V^?1 s^?1, respectively. These results offer a simple yet effective design strategy for high-performance single component semiconducting photoresists, which hold great potential for flexible electronics processed by all photolithography.

     

Electrogenerated Chemiluminescence Based on Tris(2,2′-bipyridyl) Ruthenium(II) with Hydroxyl Carboxylic Acid

Upon the electrochemical oxidation of tris(2,2′-bipyridyl) ruthenium(II) [Ru(bpy)²⁺₃] and hydroxyl carboxylic acids, for instance, citric acid, tartaric acid, malic acid, and -gluconic acid, bright electrochemiluminescences (ECLs) were observed. Different luminescent reactions were presented depending on the applied potential. The light emission was mainly caused by the reaction between alkoxide radical ion and Ru(bpy)³⁺₃below the potential +1.80 V (vs Ag/AgCl). The luminescence intensity obviously increased because of the more complex reaction process. The luminescence wavelength of 608 nm, which could be found either at higher potential than +1.80 V or in the potential range from +1.30 to +1.80 V, confirmed that ECL was caused by Ru(bpy)²⁺₃*. The factors which affect the determination and HPLC separation of the four acids were also investigated.     

Mössbauer Spectroscopic Studies of Ferrocenylaldimines and their TCNQ Complexes

A series of ferrocenylaldimines (Fc-CH=N-R) has been prepared by Schiff base condensation of formylferrocene with polyacenylamines RNH₂ where R = naphthyl, 5,6,7,8-tetrahydronaphthyl, anthracenyl, and pyrenyl groups. This step was followed by oxidation with TCNQ to give [Fc-CH = N-R][TCNQ]² salts. The electronic state of iron in these compounds was investigated by means of⁵⁷Fe Mössbauer spectroscopy.     

Synthesis and formulation of vinyl-containing polyacids for improved light-cured glass-ionomer cements

Vinyl-containing poly(acrylic acid-co-itaconic acid) copolymers were synthesized and used to formulate light-curable cements containing reactive glass fillers (Fuji II LC). The conditions for light curing were studied and optimized. Effects of molecular weight (MW), grafting ratio, comonomer, liquid composition, powder/liquid (P/L) ratio, glass powder and aging were evaluated. The results show that the vinyl-containing glass-ionomer cements (GICs) prepared in this study exhibit higher compressive strength (CS, 225.6 MPa), diametral tensile strength (DTS, 28.4 MPa) and much higher flexural strength (FS, 116.4 MPa), as compared to commercial Fuji II LC GIC (186.6 in CS, 19.1 in DTS and 57.1 in FS). The optimal light-exposure time was found to be around 10 min, and concentrations of CQ and DC were 0.5% (by weight) and 1.0%, respectively. Effects of MW, grafting ratio, P/L ratio and content of polymer in the liquid formulation were significant. The highest strengths were found for the optimal formulations where the MW was 15,000 (weight average), grafting ratio 25 mol%, P/L ratio 2.7 and liquid composition 50:20:30. During aging, the cement showed an increase of strength over the first week and then no change for a month. SEM analysis suggests that more integrated microstructures and smaller glass particles can lead to higher FS and higher polymer content in GICs leads to tough fracture surface and plastic deformation.     

氯过氧化物酶的手性催化活性在有机合成中的应用

氯过氧化物酶（CPO）作为过氧化物酶家族中的一员对多种有机底物表现出了广泛的催化活性。自上世纪60年代被发现以来，CPO在有机合成中的应用一直是一个研究热点。它作为一种生物催化剂能催化广泛的底物合成手性化合物，且有高的产率和高的对映选择率。本文综述了氯过氧化物酶在手性有机合成中的应用，重点关注了卤化、醇氧化、羟基化、环氧化、磺化氧化等反应，并讨论了目前在该领域所面临的问题及今后的发展趋势。     

Synthesis of a novel 18β-glycyrrhetinic acid derivative

A novel compound, biotinylated 18β-glycyrrhetinic acid (BGA), was synthesized. It is a compound of 18β-glycyrrhetinic acid linked with biotin. Published in Khimiya Prirodnykh Soedinenii, No. 3, pp. 266–267, May–June, 2006. An erratum to this article is available at .