Polymerization of 1,3-Butadiene with Catalysts Based on Cobalt Dichloride Complexes with Aminophosphines:Switching the Regioselectivity by Varying the MAO/Co Molar Ratio

Several novel cobalt dichloride com plexes with amino-phosphine bidentate ligands were synthesized and characterized.For some of them single crystals were obtained and their molecular structu re was determined by X-ray diffraction method.All the com plexes were then used in combination with MAO for the polymerization of 1,3-butadiene,obtaining polymers with different structures(i.e.,predominantly 1,2 or cis-1,4)mainly depending on the type of ligand and on the MAO/Co molar ratio.The behavior of ...     

“沸石分子筛及催化”专刊前言（英文）

<正>Zeolites are crystalline microporous materials with regular channels and cages of molecular size.Due to their unique structures and acidic properties,they have been widely used in the petrochemical and chemical industries since the late 1950s.Zeolites have been used as catalysts,for instance,in fluid catalytic cracking and hydrocracking.Faujasites were the first molecular sieves applied for cata-     

Triphenylamines consisting of bulky 3,5-di–tert–butyl–4-anisyl group:Synthesis,redox properties and their radical cation species

Triphenylamine(TPA) derivatives have been widely used as useful building blocks for diverse functional materials because of their excellent redox activity. Most of the molecular structures of TPA-based organic functional materials contain 4-anisyl groups, which on one hand could reduce their oxidation potential and on the other hand significantly delocalize the spin density of the resultant TPA radical cation species and enhance their stability. However, molecular-level investigation of the redo...     

Recent advance of photochromic diarylethenes-containing supramolecular systems

Photochromic diarylethenes were deemed to be one of the most promising molecular building blocks for photoresponsive materials. This review gives a brief summary to the recent progress of studies of diarylethenes in supramolecular systems, focusing on their applications in biological systems, photo-responsive mechanical materials and photo-responsive chemosensors.     

Tuning the solid-state emission of the analogous GFP chromophore by varying alkyl chains in the imidazolinone ring

New analogues of green fluorescent protein (GFP) chromophore mGFP-Cn (n = 1, 3, 5, 11) with alkyl chains of different lengths in the imidazolinone rings were synthesized and their crystal structures were determined. These GFP-like chromophores are all emissive in the solid state. And the solid-state emission quantum yields of increase by extending the lengths of alkyl chains, owing to the fact that the intermolecular pi-pi interactions are significantly weakened based on their crystal structures.     

Pervaporation for separating benzene/cyclohexane mixture by P(AA-MA) copolymer membranes

P(AA-MA)copolymers composed of acrylic acid and methyl acrylate with different molecular weights and sequence structures were synthesized by combination of ATRP and selective hydrolysis.These copolymers were used as membrane materials to separate benzene/cyclohexane mixture by pervaporation.The effects of molecular weight and sequence structure of the copolymers on the pervaporation performance were investigated in detail.For the random copolymers,the permeate flux decreased rapidly with the increasing of molecular weight.The separation factor was also influenced by the molecular weight,which was changed from no selectivity to cyclohexane selectivity with increasing the molecular weight.Contrarily,the block copolymer membrane showed good benzene selectivity with separation factor of 4.3 and permeate flux of 157 g/(m~2h)to 50 wt%benzene/cyclohexane mixture.     

Synthesis,characterization and thermal stability of novel carborane-containing epoxy novolacs

Carborane bisphenol novolacs(3 and 4) were synthesized in the presence of acid catalyst from carborane bisphenols(5 and 6) and formaldehyde. Further epoxidization of carborane bisphenol novolacs with epichlorohydrin gave carborane bisphenol epoxy novolacs(1 and 2). The molecular weight and epoxy value of obtained resins were determined using the molecular weight of their precursors. The epoxy values of 1 and 2 were 0.48 and 0.52 respectively, higher than the maximum theoretical epoxy value(0.45) of difunctional carborane bisphenol epoxy resins. FTIR and NMR were utilized to characterize 1 and 2. The curing behaviors were also studied by DSC and the optimized curing conditions were obtained.TGA analysis indicated that carborane moiety could shield its adjacent organic structures against initial decomposition. On the other hand, B―H on carborane cage could react with oxygen to form a three-dimensional network linked by B―O―B and B―C bonds, which further blocked the movement of formed radicals and thus the degradation process was inhibited.     

Surface Manipulation of Conjugated Carbon Materials with Scanning Probe Technique

The atomic force microscope (AFM) was used to manipulate surface structures of conjugated carbon materials (graphite and C₇₀) in the nanometer scale with real space resolution. Soliton superlattice was directly observed on both graphite and C₇₀ single crystals surface. The tip-induced dynamic structural changes were also investigated. 丁he manipulations of both sp³-like line defects on the lattice of graphite and individual C₇₀ molecules on defect-free surface or at molecular layer edges were suggested.     

Hydrothermal Assembly and Structural Characterization of an Octamolybdate Supported Copper (Ⅰ) Tetramer: [Cu_2(1,10-phen)_2(4,4′-bpy)]_2[Mo_8O_(26)]·4H_2O

1 INTRODUCTION The recent expansion of the field of heteropolyoxometalate chemistry derives from their vast topological structures and applicable physical properties[1～5]. One of the crucial strategies for the molecular design of solid materials is how to apply hydrothermal synthesis method to introduce some interesting transition metal coordinated fragments into the covalent backbones of solid materials. Studies have been focused on organic-inorganic hybrid materials containing one kin…     

Trans-cis isomerization of 4-(2-(9-anthryl)vinyl) pyridine.Molecular structures and ~1H NMR kinetic studies

Both cis- and trans-isomers of 4-(2-(9-anthryl)vinyl)pyridine were isolated and their molecular structures established by X-ray crystallographic method. Variable temperature 1H NMR spectroscopy was used to study the trans to cis isomerization of the title compound. The kinetic study of the reaction was based on the ratio of the NMR integration heights in toluene-d8 of the double doublet due to the cis-isomer at δ 8.51 to that of the multiplet at δ 8. 15 which was kept constant during the whole experiment. The isomerization process was found to be first order and the Arrhenius activation parameters Ea , In A ,△ H≠ and △ S≠ were calculated as 27.84kJ/mol, 6.71, 25.23 kJ/mol and - 197.89 J/(K·mol) , respectively. Besides,conformational analyses of both compounds based on molecular modelling were carried out and the results were used to compare with the experimental data.     

Oxozinc carboxylate complexes: a new synthetic approach and the carboxylate ligand effect on the noncovalent-interactions-driven self-assembly

An atom-efficient and mild synthesis of a series of oxozinc carboxylates [Zn(4)(μ(4)-O)(O(2)CR)(6)] [where R = Ph (2a), p-PhC(6)H(4) (2b), p-MeC(6)H(4) (2c), and p-MeSC(6)H(4) (2d)] from well-defined alkylzinc precursors and H(2)O is described. The molecular and crystal structures of the resulting complexes have been determined by single-crystal X-ray diffraction. A closer examination of their crystal structure provides a direct picture of the effect of the nature of substituents on the molecular self-assembly of the octahedral oxozinc through noncovalent interactions. It was revealed that these discrete oxozinc clusters can form diverse types of noncovalent assemblies ranging from structures representing zeolitic topologies in the case of 2a to soft porous materials with gated voids or open channels for the remaining molecular clusters.     

One-step Synthesis of End-Functionalized Hydrogenated Nitrile-Butadiene Rubber by Combining the Functional Metathesis with Hydrogenation

End-functionalized hydrogenated polymers obtained from nitrile-butadiene rubber (NBR) yield new materials with suitable properties for a number of applications as sealing material and adhesives. We investigated the one-step synthesis of ester end-functionalized hydrogenated nitrile-butadiene rubber (EF-HNBR) by combining the functional metathesis with the hydrogenation of NBR in the presence of the 2^nd generation Grubbs catalyst and a functionalized olefin as a chain transfer agent (CTA). We established the operating conditions for the effective production of saturated functional polymers with a high degree of hydrogenation, high chemo-selectivity and moderate molecular weight. The structures of the products were confirmed by FT-IR and ¹H-NMR spectroscopy, rubber molecular weight, and distribution determined by using gel permeation chromatography (GPC); their thermal properties were determined by thermo-gravimetric analysis (TGA) and different scanning calorimetry (DSC).     

Large-scale computational screening of zeolites for ethane/ethene separation

Large-scale computational screening of thirty thousand zeolite structures was conducted to find optimal structures for separation of ethane/ethene mixtures. Efficient grand canonical Monte Carlo (GCMC) simulations were performed with graphics processing units (GPUs) to obtain pure component adsorption isotherms for both ethane and ethene. We have utilized the ideal adsorbed solution theory (IAST) to obtain the mixture isotherms, which were used to evaluate the performance of each zeolite structure based on its working capacity and selectivity. In our analysis, we have determined that specific arrangements of zeolite framework atoms create sites for the preferential adsorption of ethane over ethene. The majority of optimum separation materials can be identified by utilizing this knowledge and screening structures for the presence of this feature will enable the efficient selection of promising candidate materials for ethane/ethene separation prior to performing molecular simulations.     

Optical behaviors of conjugated-chain compounds containing benzene and furan units

Thirteen conjugated-chain compounds which contain benzene and furan units were prepared, their optical behaviors, including UV-vis absorption coefficient (varepsilon), absorption wavelengths (lambdaa), fluorescence emission wavelengths (lambdae), and quantum yields (Phi) were measured. Meanwhile, their LUMO and HOMO energy were determined by cyclic voltammetry and their second-order polarizations (betaxxx) values were determined by solvatochromic method, respectively. The results showed that this kind of compounds possess a shorter lambdaa (320-365 nm) and performance a higher Phi values, especially for 2aa, 2ab, 2ac and 2bb, their Phi values are all more than 90%. These compounds, except 2db, showed a higher betaxxx values in DMSO, especially for 2dc (75.77x10(-30) m5 C-1) and 2dd (83.32x10(-30) m5 C-1), than that 10-methyl-acridone (6.578x10(-30) m5 C-1) or 10-benzylacridone (6.845x10(-30) m5 C-1) in DMSO did, and second harmonic generation value of 10-methylacridone and 10-benzylacridone in powder are, respectively, 1.381 and 1.861 times of that value of urea. The betaxxx values and Phi values determined for these compounds in this work were lower than these values which were desired in the original work, this phenomena was explained from their molecular structures. This work confirmed that as these compounds performance shorter lambdaa and higher Phi values, they could be good blue-color optical materials for some fields, such as OLED materials, two-photo absorption materials, fluorescent dyes.     

The influence of molecular structure on helical twisting power of chiral azobenzene compounds

Photochromic chiral azobenzene compounds with different molecular structures were synthesized, and a cholesteric phase was induced by mixing each chiral azobenzene compound with a non-photochromic chiral compound in a host nematic liquid crystal, E44. Helical pitch and, thus, helical twisting powers (HTP) of the chiral azobenzene compounds and the non-photochromic chiral compound were determined by Cano's wedge method. Molecular structures of the chiral azobenzene compounds were predicted by means of determining their molecular aspect ratio (L/D) with semiempirical molecular calculations (MOPAC at PM3 level). The effects of molecular structure on HTP of the chiral azobenzene compounds are studied in detail. Molecular structures of chiral azobenzene compounds significantly influence their HTPs.     

Spectroscopic,structure, and DFT studies of cationic palladium(II) complexes with imidazole derivative ligands

Two palladium(II) complexes with imidazole derivative ligands have been synthesized. The molecular structures of the complexes were determined by X-ray crystallography and their spectroscopic properties were studied. Based on the crystal structures, computational investigations were carried out to determine the electronic structures of the complexes. The electronic spectra were calculated with use of time-dependent DFT method, and the transitions were correlated with the molecular orbitals of the complexes. The emission of the complex with 1-methylimidazole was examined.     

Spectroscopic,structure and DFT studies of palladium(II) complexes with pyridine-type ligands

Five palladium(II) complexes with pyridine derivative ligands have been synthesized. The molecular structures of the complexes were determined by X-ray crystallography, and their spectroscopic properties were studied. Based on the crystal structures, computational investigations were carried out in order to determine the electronic structures of the complexes. The electronic spectra were calculated with the use of time-dependent DFT methods, and the electronic spectra of the transitions were correlated with the molecular orbitals of the complexes. The emission properties of the complexes have been examined.     

Morphology and persistence length of amyloid fibrils are correlated to peptide molecular structure

The formation of amyloid fibrils is a self-assembly process of peptides or proteins. The superior mechanical properties of these fibrils make them interesting for materials science but constitute a problem in amyloid-related diseases. Amyloid structures tend to be polymorphic, and their structure depends on growth conditions. To understand and control the assembly process, insights into the relation between the mechanical properties and molecular structure are essential. We prepared long, straight as well as short, worm-like β-lactoglobulin amyloid fibrils and determined their morphology and persistence length by atomic force microscopy (AFM) and the molecular conformation using vibrational sum-frequency generation (VSFG) spectroscopy. We show that long fibrils with near-100% β-sheet content have a 40-times higher persistence length than short, worm-like fibrils with β-sheet contents below 80%.     

Structures, electronic states, photoluminescence, and carrier transport properties of 1,1-disubstituted 2,3,4,5-tetraphenylsiloles

The excellent electroluminescent (EL) properties of 1,1-disubstituted 2,3,4,5-tetraphenylsiloles, 1-methyl-1,2,3,4,5-pentaphenylsilole (MPPS), and 1,1,2,3,4,5-hexaphenylsilole (HPS) have been found. Despite some studies devoted to these materials, very little is known about the real origin of their unique EL properties. Therefore, we investigated the structures, photoluminescence (PL), and charge carrier transport properties of 1,1-disubstituted 2,3,4,5-tetraphenylsiloles as well as the effect of substituents on these characteristics. The single crystals of the three siloles involving 1,1-dimethyl-2,3,4,5-tetraphenylsilole (DMTPS), MPPS, and HPS were grown and their crystal structures were determined by X-ray diffraction. Three siloles have nonplanar molecular structures. The substituents at 1,1-positions enhance the steric hindrance and have predominant influence on the twisted degree of phenyl groups at ring carbons. This nonplanar structure reduces the intermolecular interaction and the likelihood of excimer formation, and increases PL efficiency in the solid state. The silole films show high fluorescence quantum yields (75-85%), whereas their dilute solutions exhibit a faint emission. The electronic structures of the three siloles were investigated using quantum chemical calculations. The highest occupied molecular orbitals (HOMOs) and the lowest unoccupied molecular orbitals (LUMOs) are mainly localized on the silole ring and two phenyl groups at 2,5-positions in all cases, while the LUMOs have a significant orbital density at two exocyclic Si-C bonds. The extremely theoretical studies of luminescent properties were carried out. We calculated the nonradiative decay rate of the first excited state as well as the radiative one. It is found that the faint emission of DMTPS in solutions mainly results from the huge nonradiative decay rate. In solid states, molecular packing can remarkably restrict the intramolecular rotation of the peripheral side phenyl ring, which has a large contribution to the nonradiative transition process. This explains why the 1,1-disubstituted 2,3,4,5-tetraphenylsiloles in the thin films exhibit high fluorescence quantum yields. The charge carrier mobilities of the MPPS and HPS films were measured using a transient EL technique. We obtained a mobility of 2.1 x 10(-)(6) cm(2)/V.s in the MPPS film at an electric field of 1.2 x 10(6) V/cm. This mobility is comparable to that of Alq(3), which is one of the most extensively used electron transport materials in organic light-emitting diodes (LEDs), at the same electric field. The electron mobility of the HPS film is about approximately 1.5 times higher than that of the MPPS film. To the best of our knowledge, this kind of material is one of the most excellent emissive materials that possess both high charge carrier mobility and high PL efficiency in the solid states simultaneously. The excellent EL performances of MPPS and HPS are presumably ascribed to these characteristics.