Molecular dynamics simulations of LiCl association and NaCl association in water by means of ABEEM/MM

Constrained molecular dynamics simulations have been used to investigate the LiCl and NaCl ionic association in water in terms of atom-bond electronegativity equalization method fused into molecular mechanics (ABEEM/MM). The simulations make use of the seven-site fluctuating charge and flexible ABEEM-7P water model, based on which an ion-water interaction potential has been constructed. The mean force and the potential of mean force for LiCl and NaCl in water, the charge distributions, as well as the structural and dynamical properties of contact ion pair dissociation have been investigated. The results are reasonable and informative. For LiCl ion pair in water, the solvent-separated ion pair configurations are more stable than contact ion pair configurations. The calculated PMF for NaCl in water indicates that contact ion pair and solvent-separated ion pair configurations are of comparable stability.     

Synthesis and Characterization of Donor-Acceptor-Donor Triads Containing Tetrathiafulvalene and Naphthalene Diimide Units： Towards Regulation of the Intermolecular Charge-Transfer Interaction by Varying the Attached Side Groups

Introduction Extensive studies have been performed on electron donor-acceptor supramolecular systems, which have been used as models to investigate charge-transfer interactions,1 photoinduced electron and energy transfer reactions (for understanding the natural photosynthesis mechanisms).2 In recent years, molecular devices such as molecular shuttles and molecular switches based on electron donor-acceptor supramolecules have been proposed and studied.3 Since the synthesis of tetrathiafulvalene…     

THE CALCULATIOM OF CHEMXCAL SHIFTS IN SUBSTITOTED PYRIDINES

<正> The principle and method for the calculation of chemical shifts of substituted benzenes have been extended to calculation of the cheiiical shifts in substituted pyridines. We have set up a series of empirical parameters for calculation of the chemical shifts. The calculated results of 154 δ values frou 54 compounds show that the standard deviation between the calculated and the experimental values is 0 . 09 ppm. The combination of the coupling constants can be used to provide a criterion for the determination of molecular structure in substituted pyridines and to assign NMR parameters for the experiment of proton simulated spectra of substituted pyridines.     

A QSRR Study on the Chromatographic Retention Indices of Hydroxylated Polychlorinated Biphenyls

Hydroxylated Polychlorinated Biphenyls (HO-PCBs) are the metabolite of polychlorinated biphenyls and have drawn much attention because they have hazard on human health and ecosystems. Molecular connectivity index calculation has been performed for 19 HO-PCB compounds. A number of statistically based parameters have been extracted. Linear relationship between chromatographic retention index (RI) and the molecular connectivity index of 15 compounds in the training set has been established by multiple linear regression method. The other 4 HO-PCBs are used as the external test set. The result shows that the parameters can be well used to express the quantitative structure-retention relationship (QSRR) of HO-PCBs. Good stability and predictive ability have been demonstrated by leave-one-out cross-validation and the external test set.     

Light controlled imaging probes for intracellular target recognition:photochromism as a tool to enhance sensing precision

正Chemosensors and imaging probes have been the focus of significant research interest over the past few decades.In part due to ease of preparation and simplicity in manipulation,fluorescent probes have been extensively used for biomedical applications.When used for in vitro cell imaging[1,2],the     

The “twinkling star” materials: highly superior molecular switches for bioimaging

<正>Artificial molecular switches have been the robust tools for diverse fields of modern science and technology, including molecular machines, smart materials, and bioimaging [1].The development of new concepts to enable the creation of efficient molecular switches has been a longstanding activity in these fields. Up to date, various kinds of molecular switches have been developed, most of which work between     

Dynamics Studies on Molecular Diffusion in Zeolites

1 INTRODUCTION Zeolites have attracted much attention in both scientific and industrial areas for their special characteristics and multiple uses. Zeolites are composed of TO4 (T = Si, Al, Ga, P, etc.) tetrahedra which are connected with each other by sharing oxygen atoms to produce a complex and repetitive three-dimensional atom network with regular molecular dimension cavities joined by channels. Shape selectivity is the most important property of zeolites. Combined with the possib…     

THE CALCULATION OF CHEMICAL SHIFTS IN DISUBSTITUTED NAPHTHALENES

<正> The principle and method for calculating the chemical shifts of substituted benzenes have been extended to the calculation of chemical shifts in disubstituted naphthalenes. We have set up a series of empirical parameters for the calculation of chemical shifts. The calculated results of 439 8 values from 78 compounds show that the standard deviation between the calculated and the experimental values is 0.08 ppm. The combination of this calculation with that of the coupling constants can be used to provide a criterion .for the determination of molecular structure in disubstituted naphthalenes as well as to assign NMR parameters for the experiment of proton simulated spectra of disubstituted naphthalenes.     

Characterization of Microporous Alumino-borate B-C8 by 27A1 and 11B Nuclear Magnetic Resonance Spectroscopies

Late in 1970's, a new series of molecular sieves, aluminophosphates was discovered in the Union Carbide Laboratories, which have been used as catalysts for petroleum and chemical industries. Recently several novel types of zeolitic microporous aluminoborates named as B-C_n have been synthesized from a mixture of Na_2OCaO-B_2O_3-Al_2O_3-R-H_2O(R=templates) by Xu and his co-workers. Most of them     

An Empiric Linear Formula between the Internal Tetrahedron Symmetric Stretch Frequency and the Al Content in the Framework of KL Molecular Sieves

Since 1960's zeolite molecular sieves materials have been widely used in catalysis, adsorption, separation, host-guest chemistry and supramolecular science. During the research and application, the framework compositions of zeolite molecular sieves materials usually have to be determined, especially when the framework compositions are modified. Based on X-ray diffraction (XRD) peak positions and infrared (IR) spectroscopy frequencies, some empiric linear relationships have been reported t…     

A-π-D-π-A small-molecule donors with different end alkyl chains obtain different morphologies in organic solar cells

The small molecular donors with different end alkyl chains provide appropriate phase separation and molecular stacking orientation for all-small-molecule solar cells. The power conversion efficiency (PCE) have been improved obviously, and the highest PCE reaches 7.06%. The results demonstrate that the optimized end alkyl chains can be used to design A-π-D-π-A backbone structure small molecular electron donors for small-molecule organic solar cells.     

Synthesis and crystal structure of pyridine and methanol coordinated a-octabutyloxyphthalocyaninatocobalt (II)

Phthalocyanines (Pcs) have been widely used as dyes and pigments, photoelectric materials and catalysts. They also bring general attention for potential applications, for example, in solar batteries and fuel cell, charge battery, electrochromic display devices, liquid crystal, sensors and molecular devices. The Pc抯 properties, such as spectroscopic, electronic, and magnetic properties, thermostabilities, and catalytic activities, may be adjusted by modifying the molecular structure. Therefor…     

Synthesis of Some New Derivatives of 1,3-Dichloro-1,1,3, 3-tetraphenyldisilazane

Recently, the silicon-nitrogen compounds have received more consideration for their attractive application prospects. Both low molecular weight silazane and polysilazane with high molecular weight are widely used in many aspects. For example, in the processing industry of silicone rubber, silizanes not only can be used as "structure-control additives"1, but also can be used to improve the rubber's heat-resistance and mechanical properties; silicon-nitride ceramics can be prepared by pyrolysis …     

Photochemical properties of carotenoids: what can we get from the VB model?

Photo-isomerization and anti-oxidation of carotenoids have been studied for many years be-cause of their diverse roles in photobiology, photochemistry and photomedicine[1—6]. The experi-mental works revealed that the changes in the geometry between S0 (the ground state) and T1 (the first triplet state) states are very important for the two processes. Meanwhile, theoretical studies have also been carried out to investigate these processes. The polyenes have usually been used as the models for…     

A New Strategy for Architecture of Robust Monolayer Based on Binuclear Palladium (II) Complex of Calix[4]arene Derivative

Since calixarenes and their derivatives have unique coordination abilities to metal ions and inclusion abilities toward neutral organic molecules, they have been widely studied in the field of molecular recognition, transportation and separation1. In order to explore these functions, membranes such as monolayers and Langmuir-Blodgett (LB) films formed by calixarenes, are often used for these purposes2-6. However, a crucial factor that hinders their application is the weak mechanical strength …     

Insight into the Urea Binding and K166R Mutation Stabilizing Mechanism of TIpB： Molecular Dynamics and Principal Component Analysis Study

Chemoreceptor TlpB（Tlp=transducer-like protein）, which has been demonstrated to respond to pH sensing function, is crucial for the survival ofHelicobacterpylori（H, pylori） in host stomach. Urea was proposed to be essen- tial for TlpB＇s pH sensing function via binding with the Per-ARNT-Sim（PAS） domain of TlpB. Additionally, KI66R mutation of the TlpB protein has also been proven to have a similar effect on TlpB pH sensing as urea binding. Al- though X-ray crystallographic studies have been carried out for urea-bound Tlpl3, the molecular mechanism for the stabilization of TIpB induced by urea binding and K166R mutation remains to be elucidated. In this study, molecular dynamics simulations combined with principal component analysis（PCA） for the simulation results were used to gain an insight into the molecular mechanism of the stabilization of urea on TlpB protein. The formed H-bonds and salt-bridges surrounding Aspll4, which were induced by both urea binding and K166R mutation of TIpB, were im- portant to the stabilization of TlpB by urea. The similarity between the urea binding and K166R mutation as well as their differences in effect has been explicitly demonstrated with computer simulations at atomic-level. The findings may Dave the wav for the further researches of TlpB.     

In situ molecular level visualization of RAFT polymerization by AIEgen-labelled agents

正Can we see clearly the whole polymerization process?Normally, it is difficult and thus is a dream for researchers in polymer science. That is why techniques for monitoring the polymerization process have always been a major focus in both academic and industrial field owing to their potential for quality control and process optimization. Several methods,such as rheometry, viscometry and dilatometry, have been developed to study the kinetics of polymerization process.However, these methodologies examine only the macroscopic viscosity instead of at the molecular level. Online     

Molecular Weight Determination of Ring Shaped Polystyrene by Viscosimetry and Ultracentrifuge Sedimentation

Two equations for the molecular weight determination of ring shaped polystyrene and in toluene at 25℃ have been derived and identified by light scattering,viscometry and ultracentrifugc method.     

Synthesis and Crystal Structure of Dibromo [1,1′- bis(diphenylphosphino)ferrocene]cadmium(II)

1 INTRODUCTION The transition metal complexes containing ferrocene ligand arouse the interest of chemists because of their novel structures and special properties[1]. The ferrocene derivatives have been used in electrochemistry, in nonlinear optics, and as molecular ferromagnets. Some complexes of 1,1′-bis(diphenylphosphino)ferrocene (dppf) have been synthesized, and many of their crystal structures have been reported by far[2~5]. Here we report the synthesis and crystal structure of a …