Excited state dynamics and structures of functionalized phthalocyanines. 1. Self-regulated assembly of zinc helicenocyanine

Recently synthesized zinc helicenocyanine (ZnHc), where four helicene groups are fused with a phthalocyanine (Pc) core through all-carbon linkages, exhibits an unusually strong tendency of forming soluble molecular aggregates in organic solvents. The aggregation results in a strong optical absorption across most of the visible region, which is drastically different from that of its monomer. The aggregation is suppressed by dissolving ZnHc in a liquid crystal, octylbiphenylcarbonitrile (OBCN), where the monomer ZnHc dominates and exhibits a typical optical absorption spectrum of monomeric zinc phthalocyanine, except red shift in both Q- and B- bands due to pi-conjugation expansion. This study correlates optical properties and excited state dynamics of ZnHc with intra- and intermolecular electronic interactions, using quantum mechanical calculations and ultrafast transient absorption spectroscopy. Structural details of the aggregates are revealed by small-angle X-ray scattering (SAXS) to be uniformly dimers with alkoxy chains wrapped around the core of a face-to-face dimer. The results suggest that while the peripheral helicene moieties in ZnHc are electronically coupled to the Pc core via expansion of the pi-conjugation of the macrocycle, the coupling is attenuated by the "lock washer" conformation of the nonplanar peripheral helicenes which prevents pi-conjugation throughout the entire macrocycle. The interplay between pi-conjugation expansion in the macrocyle plane and the pi-pi stacking out of the macrocyle plane produces a structure that facilitates the unique optical properties and self-regulated assembly into nanoscale structures in solution. These novel optical properties are explored for potential applications in various areas.     

含氟表面活性剂溶液的动态表面张力研究

本文研究了阳离子氟表面活性剂CF₃CF₂CF₂O(CF(CF₃)CF₂O)₂CF(CF₃)CONH(CH₂)₃N⁺(C₂H₅)₂CH₃I^-(简写FC-4 )的动态表面性质，利用Krüss K12和MBP动态表面张力仪分别测定了该体系的平衡表面张力和动态表面张力。由平衡表面张力测定结果得到了临界胶束浓度和表面吸附量。利用渐进的Ward and Tordai方程对动态数据进行了分析。结果表明：在吸附的最初阶段符合扩散控制模型，而在吸附的后期，证明了吸附势垒的存在，表明在吸附后期属于混合动力学模型。计算得出25 ℃时，该体系势垒约在25到35 kJ/mol. 由于氟表面活性剂分子间作用力小，表面压是导致吸附势垒的主要原因。     

Substituent effect on photochromism of indolinospirooxazines

The photochromic reactions of five indolinospirooxazine derivatives ( II, III, V and VII) were examined using nanosecond laser flash photolysis techniques. Photolysis of II–V leads to the formation of long-lived photomerocyanines (PMCs), whereas the only detectable product in the photolysis of CII is a short-lived, charge-separated, twisted species (CT intermediate). The results show that the substituent in the 2′ position of the oxazine ring has a decisive role on the photochromic reaction products and all of the substituents influence the absorption maxima of the photoproducts of indolinospirooxazines. A proposed potential energy surface model has been established to explain these phenomena. Moreover, the characteristics of the absorption spectra of the PMCs and CT intermediate are discussed.     

交联聚苯乙烯包覆二氧化锆柱填料的制备与评价

交联聚苯乙烯包覆二氧化锆固定相是在溶液体系中通过自由基引发乙基苯乙烯、二乙烯基苯和乙烯基二氧化锆共聚反应获得。IR和SEM表征这种填料的表面特征，考察了这种交联聚合物包覆柱填料的色谱性能和化学稳定性，并用这种填料分离了苯甲酸酯类和碱性化合物。     

Nanobelt self-assembly from an organic n-type semiconductor: propoxyethyl-PTCDI

Nanobelt structures have been fabricated for an n-type semiconductor molecule, N,N'-di(propoxyethyl)perylene-3,4,9,10-tetracarboxylic diimide (PTCDI). The short alkyloxy side chain not only affords effective pi-pi stacking in polar solvents for self-assembling but also provides sufficient solubility in nonpolar solvents for solution processing. As revealed by both AFM and electron microscopies, the nanobelts have an approximately rectangular cross section, with a typical thickness of about 100 nm and a width in the range of 300-500 nm. The length of the nanobelts ranges from 10 to a few tens of micrometers. The highly organized molecular packing (uniaxial crystalline phase) has been deduced from the measurement of electron diffraction and polarized microscopy imaging. The detected optical axis is consistent with the one-dimensional stacking of the molecules.     

Mechanical stability and transport properties of the Sn-promoted SrCo0.8Fe0.2O3−δ ceramic membrane

In this article, the phase compositions, thermal, mechanical and transport properties of both the SrCo_0.8Fe_0.2O_3−δ (SCF) and the SrCo_0.8Fe_0.1Sn_0.1O_3−δ (SSCF) ceramic membranes were investigated systematically. As compared with the SCF membrane, the SSCF one had a more promoted thermal shock resistance, which related to its small thermal expansion coefficient between them and an enhanced composite structure for it. For the SCF membrane, a permeation rate of 1.9 × 10⁻⁶ mol cm⁻² s⁻¹ was obtained at 1000 °C and under the oxygen partial pressure gradient of P_O2 (h)/P_O2 (l) = 0.209 atm/0.012 atm; however, the permeation rate was 2.5 × 10⁻⁶ mol cm⁻² s⁻¹ for the SSCF one in the same measuring condition. In addition, both peak values of total electrical conductivity (σ_e) for SSCF sample appeared with increasing temperature. The second peak value of σ_e for SSCF one was regarded as the contribution from its minor phase, which appeared with the mixed conducting behavior resulting from partly Co-dissolving into its lattice.     

双硅烷热分解的理论研究

用量子化学方法研究了双硅烷１，２－氢迁移热分解，全参量优化了反应物及产物的平衡几何构型，找到了反应途径，获得了过渡态，并对过渡态进行了振动分析，活化能的计算值与实验值一致，从理论上证明双硅烷通过１，２－氢迁移的热分解途径的可行性。     

Electrochemical characterization of self-assembled thiol-porphyrin monolayers on gold electrodes by SECM.

Herein, the scanning electrochemical microscopy (SECM) approach is applied to study the formation of thiol-porphyrin self-assembled monolayer (SAMs). Using cyclic voltammetry (CV), the formation process is characterized adopting different probe molecules. The observed phenomena indicate that the formation process is affected by solution properties and the molecular structure of the probe molecules. In K(3)Fe(CN)(6) , the SAMs show a strong electron-transfer (ET) blocking effect on a pure porphyrin-modified electrode. However, addition of metal ions to the porphyrin molecules leads to ET. A consistent tendency is observed throughout the modification process using CV and SECM methods. Furthermore, k(eff) values, the apparent heterogeneous rate constants, obtained for different modification periods affirm the validity of these results. SECM images are used to collect surface information in the course of the modification process when the substrate potential is 0.5 V versus Ag/AgCl. The effect of the substrate potential indicates that the oxidation of the porphyrin molecules is supported by more positive potentials because of the similar bimolecular reaction of the porphyrin ring with positive charge and the probe molecules with negative charge.