有场和无场下高价乙炔阳离子的理论研究

使用(U)B3LYP方法,选用6-311++G(d,p)基组,研究了在无场和不同外加电场强度下高价乙炔阳离子[C2H2n+(n = 2, 3 4)]的结构、稳定性以及去质子化解离反应。我们的研究表明,在无场下,C2H22+和C2H23+是稳定的,但是C2H24+并不稳定,而是自发解离生成两个C+和两个H+,C2H24+的这种解离归因于库仑爆炸。当外加电场强度达到0.06 a.u.时,C2H22+自发解离生成C2H+ + H+,而对于C2H23+,当外加电场仅仅为0.0075 a.u.时,就自发解离生成C2H2+ + H+,C2H22+和C2H23+在场中的这种自发解离可以归结为场致解离。此外,使用(U)B3LYP方法计算了在无场和有场下由C2H2电离生成C2H22+、C2H23+和C2H24+的绝热电离能和垂直电离能。     

Study of the mesomorphic behaviour through the structure modification of azo and acetylene pyridinium and imidazolium-based ionic liquid crystals

ABSTRACT

In this work, 14 pyridinium and imidazolium-based ionic liquid crystal (ILC) with azo (N=N) and acetylene (C≡C) as linking group were synthesised in high yields and completely characterised. The structure of the molecules were planned in order to allow a complete investigation on how modifications such as presence and position of charges, linking group, number of alkoxy chains and their length affect the thermal stability and liquid crystalline behaviour. All compounds were thoroughly investigated using polarised optical microscopy (POM), differential scanning calorimetry (DSC), X-ray diffraction (XRD) measurements and thermogravimetric analysis (TGA). While the presence of charges favoured a liquid crystalline behaviour, especially SmA (and SmA₂) phase, a decrease of thermal stability was noticed. A strong dependence of the charge position and a preference for monolayer or bilayer molecular organisation was observed. On the other hand, it was demonstrated that the addition of a second alkoxy chain promoted layer distortions in some molecules, resulting in the formation of Smà and Cub phases. Also a direct comparison between the N=N and C≡C linking groups was realised, along with further comparison with literature data. The structure–properties are investigated in detail.     

Synthesis of 1,4,5,16-tetrahydroxytetraphenylene

This paper concerns the synthesis of 1,4,5,16-tetrahydroxytetraphenylene, which may function as a building block for the construction of molecular scaffolds. The synthesis of 1,4,5,16-tetrahydroxytetraphenylene was realized by stepwise Diels-Alder reactions to form two benzene rings using 1,10-dimethoxydibenzo[a,e]cyclooctene as a precursor. This key intermediate, in turn, could be obtained by photo-rearrangement of its corresponding barrelene.     

Polyaromatic amines. Part 4: Synthesis of poly(ethynyl) linked aromatic amines

The title compounds were synthesised and characterised as part of a study into new aromatic amines for charge transporting materials. Each compound was characterised by cyclic voltammetry. A qualitative estimate of the intramolecular charge mobility was deduced from the difference between the first and second oxidation potentials.     

Radical polymerization of 4-methylene-4H-1,3-benzodioxin-2-ones: Cyclic α-substituted styrenes

4-Methylene-4H-1,3-benzodioxin-2-one (MBDOON), an α-substituted cyclic styrene derivative, was synthesized and polymerized readily with 2,2′-azobis(isobutyronitrile) (AIBN) as an initiator in solution. The kinetics of the MBDOON homopolymerization with AIBN was investigated in N-methyl-2-pyrrolidone (NMP). The rate of polymerization, R_p, can be expressed by R_p ? k[AIBN]^0.52[MBDOON]^1.1 and the overall activation energy has been calcualted to be 75.7 kJ/mol. Monomer reactivity ratios in copolymerization of MBDOON (M₂) with styrene (M₁) are r₁ = 0.31 and r₂ = 3.20, from which Q and e values of MBDOON can be calculated as 3.0 and ?0.7, respectively. Ring-substituted MBDOON monomers such as 6-chloro, 6-methyl, and 7-methoxy derivatives were synthesized and polymerized with AIBN. The 6-substituted MBDOON's readily underwent radical polymerization while the 7-methoxy-MBDOON was slower to polymerize. Poly(MBDOON) is predominantly heterotactic. (rr = 35, mr = 46, and mm = 19%). The polymer releases carbon dioxide at about 200°C and is converted with some depolymerization to poly[(o-hydroxyphenyl)acetylene]. The thermolysis temperature is very much affected by the ring substituent. The onset of carbon dioxide liberation was observed at 140°C in the case of the 7-methoxyl derivative while the 6-substituents had a smaller effect on the decarboxylation temperature. © 1993 John Wiley & Sons, Inc.     

First Example of Construction of a Pyrrole Ring Bonded to a Steroid System by the Trofimov Reaction

The oxime of ⁵-pregnen-3-ol-20-one reacts with acetylene in the KOH-DMSO system to form a mixture of products containing 3-vinyloxy-17-(1-vinyl-2-pyrrolyl)-⁵-androstene as the major product (63% yield) and also the O-vinyloxime of 3-vinyloxy-⁵-pregnen-20-one (10%), 3-vinyloxy-17- and 3-vinyloxy-17-⁵-pregnen-20-one (25%, 1:4 ratio).     

Nucleophilic addition to acetylenes in superbasic catalytic systems. 12. Vinylation of lupinine

The addition of a natural alkaloid lupinine to acetylene in the presence of superbasic catalytic systems (KOH—DMSO, KOBu^t—DMSO, KOH—dioxane) under elevated or atmospheric pressure affords O-vinyllupinine (in up to 88% yield), a promising optically active monomer and intermediate for the preparation of new quinolizidine alkaloids. The same vinyl ether was obtained (in 60% yield) by the reaction of lupinine with vinyl acetate in the presence of Hg(OAc)₂.     

Umsetzungen von Halbsandwich-Rhenium(V)-Oligochalkogenidkomplexen mit Acetylen-dicarbonsäuredimethylester. Molekülstrukturen der neuen 1,2-Dicarbomethoxy-ethen-1,2-dichalkogenat-Chelatverbindungen Cp*Re[S2C2(COOMe)2]2 und Cp*Re(NtBu)[Se2C2(COOMe)2]

Reactions of Halfsandwich Rhenium(V) Oligochalcogenide Complexes with Dimethyl Acetylene Dicarboxylate. Molecular Structures of the New 1,2-Dicarbomethoxy-ethene-1,2-dichalcogenate Chelate Compounds Cp*Re[S₂C₂(COOMe)₂]₂ and Cp*Re(N^tBu)[Se₂C₂(COOMe)₂] The reaction of Cp*Re(S₃)(S₄) ( 1a ) with dimethyl acetylene dicarboxylate (dmad) leads through the blue intermediate Cp*Re(S₄)[S₂C₂(COOMe)₂] ( 2a ) to the red bis(ethene-1,2-dithiolato) complex Cp*Re[S₂C₂(COOMe)₂]₂ ( 3a ). The product 3a is also formed in the reactions of dmad with the tetrasulfidorhenium complexes Cp*Re(L)(S₄) (L = O ( 4a ), N^tBu ( 5a )) while the analogous tetraselenidorhenium compounds Cp*Re(L)(Se₄) ( 4b and 5b ) are only transformed to Cp*Re(L)[Se₂C₂(COOMe)₂] (L = O ( 6b ), N^tBu ( 7b )). According to the X-ray crystal structure analyses, the (ethene-1,2-dithiolato)rhenium chelate rings in 3a are folded along the S …? S vector towards the Cp* ligand (angle between the planes ReS₂/S₂C₂ 159.2°), whereas the ReSe₂C₂ chelate ring in 7b is planar.     

Novel solvent-controlled chemoselective palladium/copper(II) halide catalyzed oligomerization of <Emphasis Type="Italic">tert</Emphasis>-butyl acetylene

Solvent-controlled chemoselective palladium-catalyzed oligomerization of tert-butyl acetylene is reported in this paper. The reaction was carried out smoothly in benzene/n-BuOH binary solvent system. When unpolar aprotic benzene was the preponderating component in the binary system, a cyclotrimerization process occurred to produce 1,3,5-tri-tert-butylbenzene via a mechanism of three acetylene molecules, inserted step by step, forming σ-butadienyl-Pd and σ-hexatrienyl-Pd intermediates. While when the polar, protic and strong coordinating component n-BuOH, which aids Cu(II) to cleave the C-Pd σ-bonds and solvate Pd(II), Cu(II) cations, halo anion, σ-butadienyl-Pd intermediate, etc., was increased to a certain extent in the binary solvent system, the reaction proceeded readily via a n-BuOH-promoted mechanism to give (3Z,5Z)-2,2,7,7-tetramethyl-3,6-dichloro-3,5-octadiene or (3Z,5Z)-2,2,7,7-tetramethyl-3,6-dibromo-3,5-octadiene, respectively. Possible weak hydrogen bonds and n-π weak force between n-BuOH (electron pair donor (EPD)) and tert-butyl acetylene (and σ-butadienyl-Pd intermediate, electron pair acceptor (EPA)) in the latter process were also in favor of the n-BuOH promoted pathway. Meanwhile, the coupling product 2,2,7,7-tetramethyl-3,5-octadiyne was exclusively obtained when the reaction was conducted in singular polar H₂O. Influences of the solvent, catalysts, as well as possible mechanism were discussed in this paper.