Structural and electronic properties of borazine cyclacenes

The structural and electronic properties of borazine cyclacenes (BNn) have been investigated by performing semiempirical molecular orbital self-consistent field calculations at the level of AM1 method within the RHF formulation. It has been found that as the number of borazine rings increases in the arenoid belt the structures become more exothermic.     

N－甲基-吡咯烷并[3,4]C60衍生物的结构、电子光谱 和二阶非线性光学性质的 理论研究

利用半经验AM1量子化学方法研究了N－甲基－吡咯烷并[3,4]C60(MPC)及其噻吩取代衍生物(TMPC)的几何结构。电子结构研究表明,MPC及TMPC衍生物的前沿轨道主要由C60部分决定,C60母体与成基团之间存在较强的分子内电荷转移,C60部分是电子受体,而噻吩环部分和吡咯环部分为电子给体。在AM1优化几何构型的基础上,用INDO/SCI方法计算了MPC及TMPC的电子光谱,用完全态求和(SOS)公式计算了其二阶非线性光学性质。结果表明,MPC与TMPC在400nm以上均存在吸收峰,TMPC的这些吸收峰(400nm以上)比MPC的吸收峰强得多,与实验所得结果一致。对于TMPC来说,其二阶非线性光学系数β0值随分子构型不同而有较大的变化,β0值最大可达60×10^-30esu。     

Strategies for synthesizing non-bioaccumulable alternatives to PFOA and PFOS

This minireview describes the strategies for synthesis of fiuorinated surfactants potentially nonbioaccumulable.Various strategies have been focused on(Ⅰ) reducing the length of the perfluorocarbon chain,(Ⅱ) introducing hetero atoms into the fluorocarbon chain,(Ⅲ) introducing branch(herein and after branch means the fluoro-carbon chain section is not straight).In most cases,the surface tensions versus the surfactant concentrations have been assessed.These above strategies led to various highly fiuorinated(perfluorinated or not perfluorinated) surfactants whose chemical changes enabled to obtain novel alternatives to perfluorooctanoic acid(PFOA) and perfluorooctane sulphonate(PFOS).     

Structural and electronic properties of heptachlor

In this work, the molecular geometry of heptachlor is investigated using ab initio HF, DFT, LDA, and GGA methods. The natural bond orbital (NBO) analysis is performed at the B3LYP/6-311++G(d,p) level of theory. The first order hyperpolarizability β_total, the mean polarizability Δα, the anisotropy of the polarizability Δα, and the dipole moment μ, are calculated by B3LYP/6-311++G(d,p) and HF/6- 311++G(d,p) methods. The first order hyperpolarizability (β_total) is calculated based on the finite field approach. UV spectral parameters along with HOMO, LUMO energies for heptachlor are determined in vacuum and the solvent phase using HF, DFT, and TD-DFT/B3LYP methods implemented with the 6-311++G(d,p) basis set. Atomic charges and electron density of heptachlor in vacuum and ethanol are calculated using DFT/B3LYP and TD-DFT/B3LYP methods and the 6-311++G(d,p) basis set. In addition, after the frontier molecular orbitals (FMOs), the molecular electrostatic potential (MEP), the electrostatic potential (ESP), the electron density (ED), and the solvent accessible surface of heptachlor are visualized as a results of the B3LYP/6-311++G(d,p) calculation. Densities of states (DOS), the external electric field (EF) effect on the HOMO-LUMO gap, and the dipole moment are investigated by LDA and GGA methods.     

PFOS对哈维氏弧菌生长及外毒素基因的影响

探讨了全氟辛烷磺酸盐(PROS)对哈维氏弧菌密度及外毒素基因表达的影响.用含有不同浓度PFOS(5、50、500 mmol/L)的培养基培养哈维氏弧菌,分别在6、15、24 h取适量菌液,经4 000 r/min离心,磷酸盐缓冲液(PBS)洗涤3次,制成PBS菌悬液.采用实时荧光定量PCR检测其胞外蛋白酶、溶血素及保守...     

Structural and electronic properties of endohedral metallofullerenes

This account presents an overview of our achievements in structural and chemical understanding of endohedral metallofullerenes (EMFs), a new class of metal‐carbon hybrid materials formed by encapsulation of metals inside fullerene cavities. Structural determination of EMFs is of fundamental importance for understanding their intrinsic properties and the formation mechanism, and for broadening their applications. We have developed an effective method for determining the structures of paramagnetic EMFs, and also succeeded in observing the motion of cluster in a di‐metal EMF for the first time. Recently, we unambiguously established the structures of some carbide EMFs which had been wrongly assumed as conventional EMFs previously. More importantly, we have obtained some insoluble EMF species which had never been explored or even expected before. Meanwhile, the chemical properties of various EMFs with different cage structures or different metallic cores have been systematically investigated by means of both covalent and supramolecular considerations, yielding many fascinating results relating to the dictating effect of internal metals. It is noteworthy that all these achievements are based on unambiguous X‐ray results of pristine or functionalized EMFs. DOI 10.1002/tcr.201100038     

Structural and electronic properties of nanostructured HAlO

The results of a theoretical study of the nanostructured ternary compound HAlO are presented. We have considered isolated (HAlO)n clusters, the interactions between two such clusters, and two-dimensional layers of HAlO. In many of the calculations we used a parametrized density-functional tight-binding method in the calculation of the electronic properties for a given structure, combined with two different unbiased approaches, i.e., an "Aufbau" and a genetic-algorithm method, for optimizing the structure for clusters with n up to 26. The results for the isolated clusters are analyzed by means of similarity, stability, and shape parameters. Isolated structures with n up to 6 were also studied intensively with pure DFT methods.     

物化作用氧化降解PFOA/PFOS

全氟辛/磺酸（PFOX）具有环境持久、耐氧化、抗常规化学处理的特点。目前,针对PFOX的有效去除工艺研究已成为环境技术领域有机污染物降解方向的新热点。近年来,一些强氧化工艺被开发用于降解PFOX,主要通过各种物理作用增强化学氧化能力,实现PFOX的有效降解。本文综述了纯化学过程以及光、电、热、声、等离子体、微波、机械力等物理作用促进化学氧化降解PFOX的反应机理、降解途径和各因素的影响机制,以及去除效率和能耗等,介绍了该方向的最新研究进展,讨论分析了这些技术存在的问题,并提出了今后技术应用的重点研究方向。     

Structural and electronic properties of a Benzoin monomer

In the present work, we report structural and electronic properties of a benzoin monomer named as 2-oxo-1,2-diphenylethyl-2-bromopropanoate (C₁₇H₁₄BrO₃). The previously synthesized compound is characterized by single crystal X-ray diffraction. The optimized molecular geometry (bond lengths, and bond angles), HOMO-LUMO analysis and molecular electrostatic potential (MEP) are calculated by density functional theory (DFT) and Hartree-Fock (HF) methods with 6-311G(d) basis set in the neutral ground state and using DFT methods for singly oxidized doublet, singly reduced doublet, and neutral triplet state for the benzoin compound. The X-ray structure determination of the compound is compatible with the geometric parameters calculated at B3LYP/6-311G(d). In the triplet state the HOMO-LUMO energy gap of 2.39?eV which indicates semi-conductor property is recommended for the photovoltaic devices.     

Structural and electronic properties of some tetralene compounds

The PMR spectra of tetralene-2, 3-episulphide(I), -epoxide(II) and epiimine(III) have been measured and compared with those of the related compounds cis-tetralenediol-2, 3(IV) [1] and its acetal derivative(V). The electronic and structural properties of these compounds displayed some interesting trends. The data revealed the different deshielding effects of the heteroatoms.     

Structural and electronic properties of compound metal clusters

The equilibrium geometries, relative stabilities, and vertical ionization potentials of compound clusters involving Li _n , Na, Mg, and Al atoms have been calculated using ab initio self-consistent field linear combination of atomic orbitals — molecular orbital (SCF-LCAO-MO) method. The exchange energies are calculated exactly using the unrestricted Hartree-Fock (UHF) method whereas the correlation correction is included within the framework of configuration interaction involving pair excitations of valence electrons. While the later correction has no significant effect on the equilibrium geometries of clusters, it is essential for the understanding of relative stabilities. Clusters with even numbers of electrons are found to be more stable than those with odd numbers of electrons regardless of their charge state and atomic composition. The equilibrium geometries of homo-nuclear clusters can be significantly altered by replacing one of its constituent atoms with a hetero-nuclear atom. The role of electronic structure on the geometries and stabilities of compound clusters is discussed.     

Structural and electronic properties of transition metal thiophosphates

From the viewpoint of metal coordination we examine the structural characteristics of several new members of transition metal thiophosphates (i.e., MPS phases with M = V, Nb, Ta), in which various ligands such as S²⁻, S²⁻₂, and phosphorus-sulfur polyanions P_nS^x−_m (1 ≤ n ≤ 4; 3 ≤ m ≤ 13; 2 ≤ x ≤ 6) provide either an octahedral or a bicapped prismatic coordination of the metal. Tight-binding band electronic structure calculations show that the low-lying acceptor orbitals responsible for lithium intercalation of thiophosphates are their d-block bands. This prediction is confirmed by our electrochemical lithium intercalation study which reveals that the reduction sites of thiophosphates are their metal cations. Molecular orbital calculations are carried out on vanadium compounds with extremely short interligand S···S contacts. The occurrence of such short contact distances is not caused by covalent bonding in the S···S contacts but by the small size of vanadium cations which forces its surrounding sulfur ligands to squeeze one another.     

Structural and electronic properties of graphene nanotube-nanoribbon hybrids

The structural and electronic properties of a hybrid of an armchair graphene nanotube and a zigzag graphene nanoribbon are investigated by first-principles spin-polarized calculations. These properties strongly depend either on the nanotube location or on the spin orientation. The interlayer spacing, the transverse distance from the center of the ribbon and the stacking configuration affect the electronic structures. The antiferromagnetic configuration has a lower total energy than the ferromagnetic one. The interlayer atomic interactions between the two subsystems would change the low energy dispersions, open subband spacings, and induce more band-edge states. Moreover, such interactions create an energy gap and break the spin degeneracy in the antiferromagnetic configuration. The band-edge-state energies are sensitive to the nanotube location.     

Quantum chemical studies on the structures, properties and decomposition of the azido derivatives of trinitrobenzenes

The geometries,heats of formation and electronic structures of 15 azido-derivatives of 1,2,3-TNB (Ⅰ),1,2,4-TNB (Ⅱ) and 1,3,5-TNB (Ⅲ) have been studied using quantum chemical AMI method at HF level.The effect of azido substitution on the structures and properties of TNBs has been discussed and the relative stability of the title compounds has been established.The processes of the decomposition of the title compounds by breaking C-NO2,C-N3 and CN-N2 bonds are investigated at UHF-AM1 level.It is shown that the decomposition of the title compounds may be initiated by the cleavage of both C-NO2 and N-N2 bonds.     

Structural and electronic properties of hydrated MgO nanotube clusters

Hydrated MgO nanotube clusters are constructed and studied by the density functional theory at the B3LYP/6-31G(d) level. A strong exothermicity chemisorption reactivity of MgO nanotube clusters with water, which releases 137.5–171.8 kJ/mol. The averaged charge of Mg ions is steady, and presents a stronger ionic bonding. Mg ions are more sensitive to the coordination number. For the reaction of water onto clusters, electronic properties of hydrated clusters have remarkable change compared with anhydrous clusters.     

Structural and electronic properties of fluorinated boron nitride nanotubes

The effects of F doping on the structural and electronic properties of the (5, 5) single-walled boron nitride nanotube (BNNT) are investigated by using the density functional theory method. The chemiadsorption of F maintains the hexagonal BN network, increases the lattice constant, and introduces acceptor impurity states. On the other hand, substitutional doping of F destroys the hexagonal BN network, decreases the lattice constant, but does not alter the insulating feature of the BNNT. The observed insulator-to-semiconducting transition, a lattice contraction, and a highly disordered atom arrangement in the sidewall of BNNTs upon F doping appear to be most reasonably attributed to a codoping of dominating substitutional F over chemiabsorbed F, which can induce deep donor impurity states, a lattice contraction, and a destruction of the hexagonal BN network simultaneously.     

Structural and electronic properties of small platinum metallorganic complexes

A theoretical first-principles study of Pt _n (ligand) _m (n = 1–3) metallorganic complexes is performed, by varying the number of metal atoms and the nature and number of organic coordinate ligands (specifically, vinylic and arylic ligands). For each system, the nature of the bonding, the structure and the energetics of the metal/organic-species interaction are analyzed to derive information on the growth of coated metal clusters in solution. It is found that two régimes can be distinguished: a “coordinatively saturated” régime, in which the ratio among the number of ligands and the number of metal atoms is high and a ligand/organic π-interaction mode is preferred, and a “coordinatively unsaturated” régime, in which the ligand/metal ratio is low and a ligand/organic σ-interaction mode is preferred. Reactive channels, such as oxidative insertion of Pt into C–H bonds with the corresponding formation of platinum hydride species, can be opened in the latter régime.     

水分子与聚苯胺间氢键的形成对电子性质的影响

用量子化学SCF-LCAO-MO AM1方法, 对于水分子与聚苯胺(PAn)间氢键体系进行了结构优化, 从理论上系统地研究了聚苯胺分子链不同位置形成氢键的可能性以及成键方式。运用晶体轨道EHMACC方法, 对具有不同氢键结构的PAn体系进行了能带结构计算, 揭示了水分子存在和氢键的形成对PAn掺杂导电性能的贡献。氢键形成后, 能带结构变化表明有利于导电能力的提高。     

A comparative study by AM1, PM3 and ab initio HF/3-21G methods on the structure and reactivity of monosubstituted carbanion 1,2,4-triazolium ylides

A full conformational analysis of six 1,2,4-monosubstituted carbanion 1,2,4-triazolium ylides 4 a–f was performed using AM1, PM3 and HF/3-21G methods. The C-type conformers were found as the most stable structures by these different methods. This study also includes a qualitative estimation of the chemical behavior of triazolium ylides 4 a–f as nucleophilic agents on the level of ylide carbon atoms. The ab initio 3-21G method seems to be the most suitable in the characterization of these molecular systems.     

双噻吩基四硫富瓦烯富勒烯C60几何构型与电子结构的理论研究

利用半经验AM1法研究双噻吩基四硫富瓦烯富勒烯-C60(BTTTF-C60)和四硫富瓦烯-C60(TTF-C60)的几何构型、电子结构和前线轨道.计算结果显示,两化合物的TTF面发生弯曲,形成独特的空间构型,电子结构的分析表明其原因是由C60与TTF或BTTTF的相互作用引起的.C60的LUMO能与BTTTF的HOMO能接近,易发生D-A反应,形成BTTTF-C60.BTTTF-C60和TTF-C60的LUMO能仍较低.LUMO分布集中在C60部分, 表明BTTTF-C60的C60母体仍可接受电子.另外对两分子的电荷分布、 HOMO及LUMO的分析比较,表明所设计的BTTTF-C60分子可能产生与TTF-C60分子类似的电荷分离态.