聚并苯的链间作用对其导电能力的影响

采用量子化学晶体轨道ＣＮＤＯ／ ２ 方法,在考虑聚并苯链间作用的基础上对聚并苯双链模型的电子结构进行计算和讨论．结果表明：聚并苯链处于不同相对位置的链间作用对聚并苯的电荷分布规律及能带结构均有一定影响,位置不同,影响不同．从聚并苯的能带结构可以得出：聚并苯是有较小能隙、良好本征导电性能的半导体材料,考虑链间作用,对能带结构特征未有大的改变,能隙等值略有修正,导电能力有所加强．利用此模型讨论,更接近于晶体的真实结构,对进行聚并苯导电材料的性能改进将有一定帮助．     

Global reaction route mapping on potential energy surfaces of formaldehyde, formic acid, and their metal-substituted analogues

Global reaction route mapping of equilibrium structures, transition structures, and their connections on potential energy surface (PES) has been done for MCHO (M = H, Li, Na, Al, Cu) and HCO2M (M = H, Li). A one-after-another technique based on the scaled hypersphere search method has been successfully applied to exploring unknown chemical structures, transition structures, and reaction pathways for organometallic systems. Upon metal substitution, considerable changes of stable structures, reaction pathways, and relative heights of transition structures have been discovered, though some features are similar among the analogues. Al and Cu atoms were found to behave as very strong scissors to cut the CO double bond in MCHO. Energy profiles of the CO insertion into Li-H and Li-CH3 bonds were found to be very similar, especially around the structures where the Li atom is not directly connected with the methyl group, which indicates little effects of alkyl substitution on the reaction route topology.     

Pd取代对Mg2Ni及其氢化物结构和性能影响的第一性原理研究

利用基于第一性原理的密度泛函理论,计算了镁基储氢合金Mg2 Ni以及Pd取代的合金Mg12 Ni6-xPdx(x1,2,3)及其氢化物H2-Mg12 Ni6-xPdx(x=0,1,2,3)的晶体结构和电子结构.结果表明,Pd取代Mg2 Ni中的Ni原子,使其晶胞体积有所膨胀.同时,Pd的取代对Mg-Ni和Ni-Ni间的...     

Evolution of structure, transport properties and magnetism in ternary lithium nitridometalates Li(3-x-y)M(x)N, M = Co, Ni, Cu

The structures, magnetism and ion transport properties of the ternary nitrides Li(3-x-y)M(x)N (M = Co, Ni, Cu; y= lithium vacancy) were examined by powder X-ray diffraction, solid-state NMR and SQUID magnetometry. Doping levels are achieved up to x approximately = 0.4 for M = Cu and Co, but much higher substitution levels (x approximately =1) are obtained in the Li-Ni-N system. Transition metals substitute for Li at the Li(1) interplanar site and the ensuing lithium vacancies are disordered within the [Li(2)N] planes. High substitution levels in the Li-Ni-N system lead to the formation of ordered phases. Diffusion parameters, including activation energies, correlation times and diffusion coefficients, were obtained from variable-temperature solid-state NMR measurements in several ternary compounds. SQUID magnetometry shows significant variations of the electronic properties with dopant and x. The properties of the ternary nitrides can be rationalised in terms of the identity of the dopant and the structural modifications arising from the substitution process.     

Synthesis, structure, and unusual reactivity of beta-halovinyl cobalt porphyrin complexes

The preparation, structures, and reactivity of tetraphenylporphyrin (TPP) cobalt halovinyl complexes are reported. Beta-halovinyl complexes of (TPP)Co(E-CHCHX) (X = Br and I) were prepared from the insertion of acetylene into the cobalt halide bonds of the corresponding halide complexes. The reactivity of these compounds and of the previously reported (TPP)Co(E-CHCHCl), was studied in depth, and it was found that complex reactivity increased with the leaving group ability of the halide. A trans-dichlorovinyl cobalt porphyrin complex, (TPP)Co(Z-CClCHCl), was also prepared through the reaction of (TPP)CoNa and TCE. The structures of (TPP)Co(E-CHCHBr), (TPP)Co(Z-CClCHCl), and (TPP)Co(C(2)H) are reported. The C-C bond length of the vinyl group was found to vary for the beta-halovinyl complexes (TPP)Co(E-CHCHX) from 1.211 A for X = Br to 1.234 A for X = Cl and 1.320 A for (TPP)Co(Z-CClCHCl). A comparison of these structures to many chlorovinyl cobalt complexes shows that trans-2-halo substitution results in a dramatically decreased vinyl C-C bond length. The mechanism of halide substitution for the beta-halovinyl complexes was investigated with kinetic experiments that indicated a dissociative mechanism and supported the intermediacy of a cobalt acetylene complex.     

Novel functional polymers: Poly(dimethyl siloxane)–polyamide multiblock copolymers. XI. The effects of sequence regularity on the thermal and mechanical properties

Poly(aramid silicone) (PAS) multiblock copolymers were synthesized by the low‐temperature solution polycondensation of isophthaloyl dichloride (IPC) and two diamines, diamino poly(dimethyl siloxane) (PDMS; number‐average molecular weight = 1680) and 3,4′‐diaminodiphenylether (3,4′‐DAPE), in tetrahydrofuran/dimethylacetamide (2/1 v/v). Two synthetic methods for the control of the PAS sequence were used: a one‐step synthesis that presumably gave PAS with a random sequence and the polymerization of 3,4′‐DAPE with a presynthesized dimer, IPC–PDMS–IPC (two‐step synthesis), that presumably gave PAS with an alternating sequence of 3,4′‐DAPE and PDMS segments. In a ¹H NMR study of the amide protons of the 3,4′‐DAPE component in PAS, the relative length of the 3,4′‐DAPE segment of randomly sequenced PAS to that of ideally sequenced PAS could be estimated. The glass‐transition temperatures of the 3,4′‐DAPE and PDMS segments of random PAS were 152–234 and ?104 to ?117 °C, respectively, whereas the alternating PAS sequences showed no glass transition for the 3,4′‐DAPE segments. A tensile test indicated that randomly sequenced PAS behaved like a rubber‐toughened material at lower PDMS contents and like a thermoplastic elastomer at higher PDMS contents, whereas the alternately sequenced PAS behaved like a very soft rubber, showing a high value of elongation at the breaking point. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 841–852, 2003     

Rotational spectra and computational analysis of two conformers of leucinamide

Rotational spectra were recorded for two isotopic species of two conformers of the amide derivative of leucine in the range of 10.5-21 GHz and fit to a rigid rotor Hamiltonian. Ab initio calculations at the MP2/6-311++G(d,p) level identified the low energy conformations with different side chain configurations; the rotational spectra were assigned to the two lowest energy ab initio structures. We recorded 16 a- and b-type rotational transitions for conformer 1; the rotational constants of the normal species are A = 2275.6(2), B = 1033.37(2) and C = 911.71(5) MHz. We recorded 23 a- and b-type rotational transitions for conformer 2; the rotational constants of the normal species are A = 2752.775(8), B = 843.502(1) and C = 796.721(1) MHz. The rotational spectra of the (15)N(amide) isotopomer of each conformer were recorded and the atomic coordinates of the amide nitrogen were determined by Kraitchman's method of isotopic substitution. The experimentally observed structures are significantly different from the crystal structures of leucinamide and the gas-phase structures of leucine, and a natural bond orbital analysis revealed the donor-acceptor interactions governing side chain configuration.     

Preparation and absorption spectrum studies of aromatic and alicyclic poly(amide acid) ammonium salts in water and DMF and in films

A series of ammonium salts of poly(amide acid)s (PAS) were prepared from various poly(amide acid)s (PAA) with tertiary amines. The solubility of poly(amide acid) ammonium salts prepared from PAA(PMDA/ODA) in water is related to the ion concentration of tertiary amines. In order to elucidate the influence of the chemical structures of poly(amide acid)s and poly(amide acid) ammonium salts on their absorption spectra, pyromellitic dianhydride (PMDA), 3,3′,4,4 ′-biphenyltetracarboxylic dianhydride (BPDA), and 3,3′,4,4 ′-benzophenonetetracarboxylic dianhydride (BTDA) were chosen to react with p-phenylenediamine (PDA) and (4,4′-diaminodicyclohexyl)methane (DCHM) to give three kinds of aromatic PAAs and three kinds of alicyclic PAAs. The corresponding PASs were prepared by the reaction of PAAs with triethanolamine (TEA). Their ultraviolet–visible (UV–vis) absorption spectra were investigated compared to those of model compounds. A transparent film without absorption above 320 nm was obtained for PAS(PMDA/DCHM). The difference in absorption spectra of PAS(PMDA/PDA) from that of PAS(PMDA/DCHM) can be related to the existence of intra- and intermolecular charge transfer (CT) for PAS(PMDA/PDA). The absorption spectra of PASs with PDA in films are red shifted compared to those of corresponding PAAs in films, while the absorption spectra of PASs in water are blue shifted compared to those of corresponding PAAs in DMF. No differences in the absorption spectra of PAAs and PASs were found in DMF/H₂O (9/1) mixed solvent. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1329–1340, 1998     

金属卟啉及其与NO表面吸附物的FT—IR／PAS研究

光声光谱(Photoacoustic Spectroscopy,PAS)是研究凝聚态和表面吸附物振动光谱的1种新方法。近几年来PAS发展很快,它与FT-IR技术结合,已成为1种新的固体样品和表面分析的有力工具。本文应用FT-IR/PAS方法研究了金属卟啉配合物及其与NO的表面吸附物。卟啉及其金属配合物具有平面大π体系共轭环的结构特点,在光     

Stereochemistry and spin state in four-coordinate transition metal compounds

A systematic DFT computational study of the stereochemistry associated with each spin state for first transition series four-coordinate d(n) (n = 0-10) homoleptic metal complexes is presented. The stereochemistry of [MMe4](x-) complexes in the 21 spin configurations analyzed can be predicted from the d orbital occupation in the ideal tetrahedral geometry, grouped in three families with tetrahedral, square planar, or intermediate structures that can be described in some cases as sawhorses. The effect of the following factors on the spin state and stereochemical preferences has also been studied: (a) substitution of the sigma-donor methyl ligands by pi-donor chlorides, (b) a high (+4) oxidation state of the metal, and (c) substitution of the metal atom by a second transition series one. Through those factors, low-spin tetrahedral structures can be achieved, as summarized by a magic cube.     

Silver-carbon cluster AgC3: structure and infrared frequencies

Silver-carbon clusters were formed by dual Nd:YAG laser vaporization, trapped in a solid Ar matrix at 12 K, and investigated by infrared spectroscopy. Two new infrared absorption bands were observed at 1827.8 and 1231.6 cm(-1). Isotopic ((13)C) substitution experiments were performed to aid in their assignment. Possible structures considered for the carrier of these bands were Ag(m)C(n) with m = 1 and 2 and n = 1-3, all of which were investigated by density functional theory calculations. The geometries and associated vibrational harmonic-mode frequencies of these clusters were computed with the MPW1PW91 functional and SDD basis set. Both calculations and (13)C-isotopic substitution experiments indicate that the new bands are due to the asymmetric and symmetric C=C stretching modes, respectively, in near-linear AgC3.     

Syntheses and Structures of (Ga1-xBx)PO4, with a New Modification of High Cristobalite,and (B1-xZnx)PO4, with Low Cristobalite Type

The transition metal element substitutions of the industrial catalytic material ortho-borophosphate, BPO₄, can lead to either new type of structure for Cr^[1] or stabilize low cristobalite structure for Mn, Fe,Co, Ni and Cu^[2] Here we report our results on the substitution by main group elements Zn and Ga. The two title compounds were synthesized by high temperature solid state reactions and the structure were refined by powder diffraction methods.The structure parameters:(B_0.25Ga_0.75)PO₄:Tetragonal, P-4, a=4.727(1), c=7.078(1) Å,V=158.17(1) ų, Z=2, R(P)=0.0965, R(I)=0.0426; (B_0.61Zn_0.39)PO₄:Orthorhombic, C222₁ a=7.080(1), b=7.087(1),c=6.990(1) Å, V=350.71(2) ų, Z=4,R(P)=0.0904,R(I)=0.0438. Pure GaPO₄ were found three kinds of structures, low- and high-cristobalite and high -quartz with an observation of an unknown unstable high cristobalite at high temperature^[3] The boron substitution of the high-cristobalite GaPO₄ with space group I-A leads to lower symmetry space group(P-4). We assume the low symmetry structure related to the unknown unstable phase. The structures of both compounds are similar to very well known cristobalite (see figure below).     

Nucleophilic identity substitution reactions. The reaction between hydrogen fluoride and protonated alkyl fluorides

The gas phase reactions between HF and the protonated alkyl fluorides MeFH+, EtFH+, Pr(i)FH+, and Bu(t)FH+ have been studied using ab initio methods. The potential energy profiles for both nucleophilic substitution (S(N)2) and elimination (E2) pathways have been investigated. Both backside Walden inversion and frontside nucleophilic substitution reaction profiles have been generated. Backside substitution is very favourable, but shows relatively little variation with the alkyl group. Frontside substitution reaction barriers are only slightly higher than the barrier for backside substitution for HF + MeFH+, and the difference in barrier heights for frontside and backside displacement seems negligible for the larger alkyl groups. Reaction barrier trends have been analysed and compared with the results of similar studies of the H2O/ROH2+ and NH3/RNH3+ systems (R = Me, Et, Pr(i), and Bu(t)). Compared to the two other classes, protonated fluorides have extreme structures which, with the exception of the Me substrate, are weakly bound complexes between an alkyl cation and HF. The results nourish the idea that nucleophilic substitution reactions are better understood in view of competition between frontside and backside substitution than from the traditional S(N)1/S(N)2 perspective.     

G3(MP2) ring strain in bicyclic phosphorus heterocycles and their hydrocarbon analogues

[Figure: see text] The ring strain present in 2-aza-1-phosphabicyclo[n.1.0]alka(e)nes (n = 1-5) is calculated at the G3(MP2) level using homodesmotic reactions. The influence of cyclopropa(e)nation and heteroatom substitution is analyzed by a comparison with the corresponding bicyclic hydrocarbons and separate ring systems. It is shown that the strain caused by fusion with a cyclopropane is the sum of the separate rings, whereas the strain resulting from fusion with cyclopropene leads to strain energies much larger than the sum of rings, as a result of the inverted nature of the bridgehead carbon. In all ring structures but one, cyclohexane, substitution by nitrogen and phosphorus is favorable and the effect is most pronounced for the most condensed structures. The calculated strain energies correlate very well with the experimental stability and reactivity of the bicyclic iron-amino phosphirane and phosphirene complexes.     

Chemical Constituents from the Wild Atractylodes macrocephala Koidz and Acetylcholinesterase Inhibitory Activity Evaluation as Well as Molecular Docking Study

Screening the lead compounds which could interact both with PAS and CAS of acetylcholinesterase (AChE) is an important trend in finding innovative drugs for Alzheimer’s disease (AD). In this paper, four sesquiterpenes, i.e., atractylenolide III (1), atractylenolide IV (2), 3-acetyl-atractylon (3) and β-eudesmol (4), were obtained from the wild Atractylode macrocephala grown in Qimen for the first time. Their structures were elucidated mainly by NMR spectroscopy. To screen the potential dual site inhibitors of AChE, the compounds 1, 2, 3, as well as a novel and rare bisesquiterpenoid lactone, biatractylenolide II (5), which was also obtained from the tilted plant in our previous investigation, were evaluated their AChE inhibitory activities by using Ellman’s colorimetric method. The results showed that biatractylenolide II displayed moderate inhibitory activity (IC₅₀ = 19.61 ± 1.11 μg/mL) on AChE. A further molecular docking study revealed that biatractylenolide II can interact with both the peripheral anionic site (PAS) and the catalytic active site (CAS) of AChE. These data suggest that biatractylenolide II can be considered a new lead compound to research and develop more potential dual site inhibitors of AChE.     

Polymerization and Copolymerization of Allyl Allyl Sulfonate

Allyl allyl sulfonate (AAS) has been polymerized under the influence of azobisisobutyronitrile to low molecular weight polymers containing cyclic structures. This is in contrast to the behavior of allyl ethane sulfonate (AES) and of propyl allyl sulfonate (PAS) which did not polymerize under the same conditions. AAS has been copolymerized with styrene, methyl acrylate, and vinyl acetate. The following copolymerization reactivity factors have been found:

r_AAS 0.01 ± 0.01 r_styrene 13 ± 1

r_AAS 0-37 ± 0.09 r_{methyl acrylate} 5.3 ± 0-7

r_AAS 1.54 ± 0.08 r_{vinyl acetate} 0.5 ± 0.15

The results indicate that AAS has a higher reactivity than AES or PAS.     

Formation and characterization of thorium methylidene CH2=ThHX complexes

Laser-ablated thorium atoms react with methyl fluoride to give the CH2=ThHF molecule as the major product observed and trapped in solid argon. Infrared spectroscopy, isotopic substitution, and density functional theoretical frequency calculations confirm the identification of this methylidene complex. The four strongest computed absorptions (Th-H stretch, Th=C stretch, CH2 wag, and Th-F stretch) are the four vibrational modes observed. The CH2=ThHCl and CH2=ThHBr species formed from methyl chloride and methyl bromide exhibit the first three of these modes in the infrared spectra. The computed structures (B3LYP and CCSD) show considerable agostic interaction, similar to that observed for the Group 4 CH2=MHX (M = Ti, Zr, Hf) methylidene complexes, and the agostic angle and C=Th bond length decrease slightly in the CH2=ThHX series (X = F, Cl, Br).     

聚并苯纳米颗粒与聚丙烯复合制备新型抗静电阻燃材料

用聚并苯纳米颗粒作为新型导电填料代替导电炭黑和石墨等, 制备出具有抗静电阻燃性能的纳米聚并苯/聚丙烯复合材料. 测定了复合材料的渗流转变区, 讨论了纳米聚并苯含量对复合材料体积电阻率和表面电阻率的影响. 实验结果表明, 所制备复合材料的渗流转变发生在纳米聚并苯质量分数为16.7%-28.6%范围内, 当纳米聚并苯含量为28.6%时, 体积电阻率下降至2.09×107 Ω·cm. 另外, 阻燃性能研究结果表明, 当纳米聚并苯质量分数为23.1%时, 复合材料在空气中可以自熄, 因而可应用于矿井中抗静电阻燃塑料管道.     

Peripherally B and N substituted cyclacenes

AM1 (RHF) type semiempirical quantum chemical calculations have been applied to cyclacenes whose fusion points and peri positions of one of their peripheral circuits are substituted with nitrogen and boron, respectively. The structures have been found to be stable but endothermic (except for R=8 and 9) in nature. The nitrogen and boron (the fusion points peri positions, respectively,) substitution have been found to have stabilizing effect on the parent unsubstituted cyclacenes. Some geometrical and physicochemical data are also reported.