3,4‐Di‐2‐pyridyl‐1,2,5‐oxadiazole and its perchlorate salt

In 3,4‐di‐2‐pyridyl‐1,2,5‐oxadiazole (dpo), C₁₂H₈N₄O, each mol­ecule resides on a twofold axis and inter­acts with eight neighbours via four C—H⋯N and four C—H⋯O inter­actions to generate a three‐dimensional hydrogen‐bonded architecture. In the perchlorate analogue, 2‐[3‐(2‐pyrid­yl)‐1,2,5‐oxadiazol‐4‐yl]pyridinium perchlorate, C₁₂H₉N₄O⁺·ClO₄⁻ or [Hdpo]ClO₄, the [Hdpo]⁺ cation is bisected by a crystallographic mirror plane, and the additional H atom in the cation is shared by the two pyridyl N atoms to form a symmetrical intra­molecular N⋯H⋯N hydrogen bond. The cations and perchlorate anions are linked through C—H⋯O hydrogen bonds and π–π stacking inter­actions to form one‐dimensional tubes along the b‐axis direction.     

Theoretical ONIOM2 study on pyridine adsorption in the channels and intersection of ZSM-5

The structures of the acid sites in the channels and intersections of H-, Li-, and Na-ZSM-5 (ZSM = zeolite socony mobil) and their interactions with pyridine molecule have been computed by using three corresponding models containing 22 tetrahedral sites. The calculated adsorption energies of pyridine in the intersection regions of H-, Li-, and Na-ZSM-5 are 197.0, 172.5, and 122.3 kJ/mol, respectively, in good agreement with the respective experimental values of 200 +/- 5, 155-195, and 120 kJ/mol, while those in the straight and sinusoidal channels are much smaller (157.9 and 127.6, 152.2 and 149.4, and 150.4 and 109.9 kJ/mol, respectively). These indicate that the most probable adsorption site for pyridine in ZSM-5 is the acidic site located in the intersection region. The structural parameters of the adsorption complexes show that the acidic proton in the three models of H-ZSM-5 has been transferred to the nitrogen of pyridine, while in alkali cation-exchanged ZSM-5, the coordination of the alkali cation to the nitrogen atom of pyridine dominates the overall interaction. In addition, the adsorption complexes were further stabilized by the long-range electrostatic interaction between the positively charged pyridine hydrogen atoms and the negatively charged lattice oxygen atoms of the zeolite framework. In the intersection regions of H-, Li-, and Na-ZSM-5, the coordination energy of the charge-compensating cation to the pyridine nitrogen amounts to 58, 60, and 68% of the total adsorption energy, respectively, while another 42, 40, and 32%, respectively, is due to long-range electrostatic interactions. This indicates that the zeolite lattice framework surrounding the adsorption site has important contributions to the adsorption energy of the pyridine molecule.     

Chemiluminescence determination of barbituric acid using Ru(phen)(3)(2+)-Ce(IV) system

A chemiluminescence (CL) method for the determination of barbituric acid (BA) was proposed, which is based on the enhancement of BA to the CL intensity of Tris-(1,10-phenanthroline)ruthenium(II) (Ru(phen)₃²⁺)-cerium(IV) (Ce(IV)) system. The concentration of BA is proportional to the CL intensity in the range of 5.0×10⁻³-2.0 μg ml⁻¹. The detection limit is 6.9×10⁻⁴ μg ml⁻¹. The relative standard deviation (R.S.D.) of determining 11 samples containing 0.20 μg ml⁻¹ BA is 3.2%. This CL method has been successfully applied to the determination of BA in the synthetic samples. The mechanism of CL reaction was studied.     

盐卤硼酸盐化学 Ⅹ.MgO·2B2O3-MgCL2-H2O浓盐溶液在20℃时硼酸盐的结晶动力学研究

配制MgO·2B_2O—MgCl_2—H_2O浓盐溶液在20℃恒温静置过程中,第一阶段析出MgO·3B_2O_3·7H_2O,第二阶段析出2MgO·2B_2O_3·MgCl_2·14H_2O。采用一级和二级混合反应速率模型,用计算机对结晶动力学C_B—t实验曲线进行拟合,给出结晶动力学速率方程-r=-dC/dt-k(C-C_(平衡))~2+k’(C-C(平衡))。基于高硼浓盐溶液中硼氧配阴离子是以多粒子共存的设想,提出了这两种水合硼酸镁盐结晶反应过程的机制,结晶过程中溶液pH变化的测定结果证实了这一解释。     

Structure dependent packing behavior of phthalocyanine on the surface of graphite

The surface‐assembly behavior of phthalocyanine is of great importance because of the molecule's important application as an organic semiconductor in electronics and in solar cells. In this work, the surface‐assembly behavior on graphite of four metal phthalocyanines bearing different substituents was investigated by scanning tunneling microscopy. Owing to the difference in the substituents, the packing symmetries of these phthalocyanines are apparently different. The results point out that the packing mode of phthalocyanine is not only influenced by molecular symmetry but also by steric hindrance. Copyright © 2006 John Wiley & Sons, Ltd.     

Drug Discovery Based on the Structure of FKBPs： Design, Synthesis and Evaluation of L-1, 4-Thiazane-3-carboxylic Acid Derivatives as Neuroimmunophilin Ligands

Based on the structure of FK506, FKBP12 and calcineurin complex and the interactive characteristics of small molecular ligands with FKBPs, a series of L-1,4-thiazane-3-carboxylic acid derivatives as neuroimmunophilin ligands was designed and synthesized. The results of evaluation show that compound N308 has a great promise as a candidate of neuroprotective and neuroregenerative agent.     

光卤石在芒硝溶液中的溶解和转化

研究了光卤石在芒硝溶液中溶解及转化的机理，用离子浓度随时间的变化拟合得到动力学方程，并求得溶解反应的表观活化能。     

Contributions of various transmission paths to speech privacy of open ceiling meeting rooms in open-plan offices

Installing open ceiling meeting rooms inside a large open-plan office provides a solution to increase speech privacy and to reduce speech disturbance in the office. The open ceiling meeting rooms have advantages of low cost construction and flexibility, but have lower speech privacy than that of enclosed rooms due to the open ceiling. Existing research shows that many factors should be taken into account to achieve good speech privacy in open-plan offices and improving only one of these factors may result in little improvement, so it is important to distinguish contributions of different acoustic transmission paths of open ceiling meeting rooms in open-plan offices. This paper proposes an impulse response separation method to quantify contributions of various acoustic paths of open ceiling rooms on speech privacy in open-plan offices. The method is verified with simulations based on the Odeon software and the experiments carried out in 3 different types of rooms. Finally, the proposed method is applied to the Fabpod, a semi enclosed meeting room located in a large indoor office at the Design Research Institute of the RMIT University, to obtain the contributions of different acoustic transmission paths to its speech privacy. The method proposed in this paper and the knowledge obtained are useful for architects to improve the acoustic performance of the next generation Fabpods which are now under design at RMIT University.