官能化蒙脱土负载双金属催化芳香氯化物水相脱氯

用PVP(聚乙烯吡咯烷酮)络合双金属Pd^2 ,Sn^4 后，再负载于用PEG400(平均分子量为400的聚乙二醇)官能化的蒙脱土上，制成双金属催化剂PVP—PdCl2-SnCl4/Montk10-PEG400,用于催化难溶于水的芳香卤化物水相脱卤，芳香族氮化物转化率达100％，该催化剂可重复使用。对催化剂进行了IR及TEM表征。     

Purine Nucleoside Analogs. 12. Synthesis of Novel 8,9-Disubstituted Guanine Derivatives by S-Alkylation of 2-Acetamido-9-(2-acetoxyethoxymethyl)-6-oxo-8-thioxopurine

S-Alkylation of 2-acetamido-9-(2-acetoxyethoxymethyl)-6-oxo-8-thioxopurine was used to synthesize its novel S- and N₍₇₎-substituted derivatives. We have established the effect of the structure of the alkylating agent on the reaction conditions and its regioselectivity. We have shown that the synthesized guanine derivatives can be modified further.     

Fluorinated benzimidazo[1,2-a]quinolones

The reactions of 2-cyanomethylbenzimidazole with polyfluorobenzoyl chlorides afforded 2-(1,3-dihydrobenzimidazol-2-ylidene)-3-oxo-3-polyfluorophenylpropionitriles. Refluxing of the latter compounds in acetonitrile in the presence of DBU or in dimethylformamide in the presence of amines gave rise to fluorine-containing derivatives of benzimidazo[1,2-a]quinolone.     

CCl2(A1B1)被O2及取代甲烷类分子猝灭的动力学研究

对CCl4／Ar混合气体放电产生CCl2自由基，再用541.52nm激光将电子基态CCl2激发到激发态A^1B1（0，4，0）振动态k=0能级上，通过检测 激发态CCl2时间分辨荧光信号，测得室温下CCl2(A^1B1)被O2，CF4，CF2Cl，CH3NO2，CH2Br2等分子猝灭的实验结果，用改进的三能级模型分析处理实验数据，获得态分辨速常数KA和Ka值，并对实验结果进行了讨论。     

纳米CeO2基固溶体催化柴油机碳颗粒物燃烧性能

采用柠檬酸溶胶鄄凝胶法制备CeO2基固溶体催化剂(Ce0.7Zr0.3O2-δ、Ce0.7Pr0.3O2-δ和Ce0.7Gd0.3O2-δ), 并考察了固溶体和三种常用载体(TiO2、SiO2和Al2O3)及其负载KNO3后的催化碳黑燃烧活性. 结果表明, CeO2基固溶体催化剂具有很高的催化燃烧活性, 其活性接近TiO2、SiO2和Al2O3负载30%KNO3催化剂的活性. 因为纳米CeO2基固溶体的形成, 提高了催化剂的抗烧结能力, 使氧更活泼, 从而提高氧化还原性能, 有利于碳颗粒燃烧. 由于CeO2基固溶体本身的高活性, 因此KNO3的添加不能明显提高CeO2基固溶体催化剂(尤其是Ce0.7Zr0.3O2-δ和Ce0.7Pr0.3O2-δ)的催化燃烧活性, 但KNO3能显著提高TiO2, SiO2和Al2O3的催化燃烧活性.     

Substituent-controlled photoisomerization in retinal chromophore models: Fluorinated and methoxy-substituted protonated Schiff bases

The effect of substitution on the intrinsic (i.e. in vacuo) photoisomerization ability of retinal chromophore models has been explored using CASPT2//CASSCF minimum energy path computations to map the S₁ photoisomerization paths of two substituted minimal models of the retinal chromophore: the 2-cis-penta-2,4-dieniminium and the all-trans-epta-2,4,6-trieniminium cations, which have been modified using fluorine or methoxyl substituents as representative examples of electron-withdrawing and electron-releasing groups, respectively. A systematic analysis has been performed involving substitutions in all the possible positions along the chain. It is shown that the photochemical reactivity and photoisomerization efficiency of these systems may be tuned or indeed changed, although this effect strongly depends on the position of the substituent. In particular, we have shown that (i) most of the systems preserves qualitatively the reactivity of the parent (i.e. unsubstituted) compound; (ii) substitution at positions C4 or C6 leads to a different relaxed excited state structure of the chromophore and in general to a very flat photoisomerization path (or to a tiny S₁ energy barrier in some cases); (iii) the nature of the TICT state (i.e. the S₁ → S₀ decay funnel) may be turned from a conical intersection into an excited state minimum; (iv) for the C4 methoxy-substituted system the isomerization path as well as the S₁/S₀ decay funnel involve an unusual torsional angle. Thus, substitution turns out to be a good tool not only to tune the optical properties (i.e. the absorption and emission features) of the chromophore (as we have already shown in a previous work: I. Conti, F. Bernardi, G. Orlandi, M. Garavelli, Mol. Phys. 104 (2006) 915–924), but it may also play a crucial role in tuning and controlling photoisomerization selectivity and efficiency, affecting excited state lifetime and reaction rate. A rationale for these effects is presented, which provides a basis for understanding reactivity properties and the intrinsic photochemical behavior of substituted retinal chromophores.     

The Reaction of Maleic and Phthalic Anhydrides with 2-Methylimidazole

The reaction of maleic anhydride with 2-methylimidazole in acetonitrile and DMF is accompanied by the appearance of strong absorption bands in the visible part of the spectrum due to the formation of molecular complexes. In acetonitrile the reaction proceeds by two routes via the formation of an amide and the molecular complex. Phthalic anhydride reacts with 2-methylimidazole to give amide but not to form molecular complexes.     

S1←S0 Vibronic spectra and the structure of acetyl fluoride-h3 and acetyl fluoride-d3 molecules

UV absorption spectra of acetyl fluoride-h₃ and -d₃ (CH₃COF and CD₃COF) molecules in the region of S₁S₀ electronic transitions are investigated. The origins (0⁰ ₀ or 14^0± ₀) of these transitions are observed at 39912 and 39904 cm^–1, respectively, and some of the fundamental frequencies of these molecules in the s₀ and S₁ states are determined. In particular, the systems of torsion and inversion (out-of-plane C=O vibrations) energy levels are studied. The geometric parameters of an acetyl fluoride-h₃ molecule in the S₁ state are estimated by the theoretical simulation of the rotational contours of the 0⁰ ₀ (14^0± ₀) band. These data are used to evaluate the potential barriers to internal rotation in the S₀ and S₁ states, which were found to be 360 and 560 cm^–1 for acetyl fluoride-h₃ and 380 and 770 cm^–1 for acetyl fluoride-d₃, respectively, as well as the potential barriers to inversion in the S₁ states, which were found to be 2090 and 2370 cm^–1 for acetyl fluoride-h₃ and acetyl fluoride-d₃, respectively.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1957–1964, November, 1994.In conclusion, the authors would like to acknowledge T. S. Kuznetsova for the synthesis and purification of the AF samples.The research presented here was supported in part by the International Science Foundation under grant No. MJ 1000.     

Crown-containing styryl dyes

Styryl dyes containing a crown ether group and a heteroaromatic moiety with a sulfoalkylN-substituent (1a,b) undergo photocyclodimerization in acetonitrile in the presence of Mg(ClO₄)₂ to give only the typeA isomer of cyclobutane derivative (2a,b). The photochemical regio- and stereoselectivity of the cycloaddition is explained by self-organization of thetrans-isomers of the styryl dyes upon complexation with the Mg²⁺ cations into dimers with a fixed mutual arrangement of multiple bonds.For part 7, see ref. 1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1449–1452, August, 1993.     

Model studies of the chemisorption of hydrogen and oxygen on nickel surfaces

Atomic chemisorption of hydrogen and oxygen on the Ni(100) surface has been studied using an Effective Core Potential (ECP) approach described in a previous paper. Clusters of up to 50 nickel atoms have been used to model the surface. The computed chemisorption energies are 62 kcal/mol (exp. 63 kcal/mol) for hydrogen and 106 kcal/mol (exp. 115–130 kcal/mol) for oxygen. Correlating the adsorbate and the cluster-adsorbate bonds is extremely important for obtaining accceptable results, particularly for oxygen. Reasonable convergence of chemisorption energies is obtained with 40–50 cluster atoms for both hydrogen and oxygen. For hydrogen the addition of a third cluster layer stabilizes the results considerably. Both hydrogen and oxygen are adsorbed at (or close to) the four-fold hollow site. The calculated barriers for surface migration are also in good agreement with the experimental estimates. The calculated equilibrium heights above the surface are on the other hand too high compared with experiments. This disagreement is believed to be due to core-valence correlation effects, which are not incorporated in the present ECP. The cluster convergence for the height above the surface is much slower than for the chemisorption energy.