电解质-非电解质混合溶液活度系数的关联及溶解的推算 II:NH3-NaCl-Na2SO4-H2O体系的液固平衡热力学

由于在研究的体系中, Na2SO4是非对称电解质, 且能生成水合盐, 故推导了由非对称型电解质与非电解质所构成的混合溶液的各组分的活度系数关联通式, 并在此基础上讨论了水合盐液固平衡的计算方法.     

硝基甲烷热解机理的量子化学研究

用ab initio和NMDO 两种方法, 对CH~3NO~2沿C-N键断裂的热解反应过程 进行了较细致的计算研究。所得势能曲线(E-Rc-n) 彼此一致,并与Kaufman等[1]的近期结果相符。将各单点下所得正则离域化处理, 发现当C和N原子间的距离Rc-n=1.6-1.8A时, 定域成键σc-n-MO从能级较低的五的个占有MO跃升为HOMO(即第16个MO)。考察占有末占有前沿轨道 能级和位相, 可推在CH~3NO~2热 解的初抬阶段, 通过分子重排成C-O键的可能性较小 。其热解引发步骤可能是生成.CH~3和.NO~2双自由基。     

Possible key intermediates in arsenic biochemistry: Synthesis and identification by liquid chromatography electrospray ionization mass spectrometry and high resolution mass spectrometry

Arsenic is a type 1 carcinogen and its toxicity is critically dependent on chemical speciation. However, after decades of research, the biogenesis of at least fifty naturally occurring arsenic species is still not well understood.Here, based on experimental work, it is proposed a set of pathways for the formation of multiple arsenic species that might help to clarify the present situation.These are focused on the thiol protein arsenic bond and on its interaction with reactive metabolites. In fact, arsenic bound to glutathione interacting with sulfur adenosyl methionine (SAM), MethylCB₁₂ and AdoCB₁₂, forms a number of complexes that might be key intermediates in arsenic biochemistry. These include dimethylarsino glutathione (DMAG) m/z 412 [M + H]⁺, synthesized non-enzymatically from glutathione and cacodylate. Trimethylarsonio glutathione (TMAG) m/z 426 [M]⁺ synthesized from DMA, GSH and SAM, apparently by a classical Challenger methylcarbonium attack. Tetramethyl arsonium ion m/z 135 [M]⁺ is formed in a third step, apparently by carbanion methylation. The presence of trimethylarsine oxide (TMAO) m/z 137 [M + H]⁺ is attributed to the hydrolysis of TMAG or TMA, or to carbanion methylation of dimethylarsinoyl glutathione (m/z 428 [M]⁺) formed from cacodylate and GSH. Cantoni type attacks of DMAG on SAM were unsuccessful, eventually due to competition of the trivalent S⁺ atom of SAM for the As^III atom attack. The presence of dimethylarsonio diglutathione (DMADG m/z 717 [M]⁺), is suggested to result from a GS^- attack on dimethylarsenoyl glutathione (m/z 428 [M + H]⁺). The presence of dimethylarsenoyladenosine (m/z 372 [M + H]⁺), trimethylarsenosugar adenine (m/z 370 [M]⁺), and dimethylthioarsenosugar adenine (m/z 388 [M + H]⁺), is explained by the synthesis of the pecursor dimethylarsonio-adenosine glutathione DMAAG (m/z 661 [M]⁺), a likely source of oxo-and trimethylated arsenosugars, as well as of thio-arsenosugars by the cleavage of its S-C bond. The results gathered suggest that cell vacuoles might play a major role in arsenic metabolism, and that the dominance of oxo-As sugars, in algae extracts, may be supported by a mechanism of synthesis independent of DMAAG (m/z 661).They also offer an explanation for the reason why arsenobetaine, and tetramethylarsonium are loosely bound to biotic tissues. Four arsenic species new to science, to the best of our knowledge, and a number of known arsenic compounds were synthesized in this work, identified by HPLC–ESI-MSⁿ and FTICR–ESI-MS, and suggestions regarding their mechanisms of synthesis were advanced. These results provide a framework for arsenic biochemistry which may explain the origin of a significant part of arsenic known metabolites.     

Rg—HX(Rg=He,Ne;X=F,Cl,Br)分子间势的精确量子化学从头计算研究III.He—HBr

在用非迭代的三重激发项来校正CCSD的CCSD（T）理论水平下,采用aug-cc- pVQZ基函数对He—HBr的分子间势进行了系统的研究。结果表明：He—HBr以线型结 构存在。在极限基的情况下,复合物两种线型极小点结构He—H—Br和He—Br—H势 阱深分别为28.792 cm~(-1)和35.707 cm~(-1),对应He原子到HBr分子质心的距离 R分别为0.407 nm和0.343 nm。讨论了不同的基函数和理论方法在研究此类弱束缚 态复合物的分子间势时的可靠性及其对结果的影响,同时也给出了热函数的解析形 式。     

低温基质隔离红外光谱和从头算研究CF~2O...IF

在10KAr和Xe基质中测得CF~2O...IF的两种分子间配合物A和B的红外光谱,观察到A和B之间的异构化反应。采用量子化学从头计算,在MP2/LANL2DZ水平上计算得到A和B的平衡构型的结构参数和振动频率。IF与CF~2O的相互作用引起CF~2O的C=O双键伸长、C-F键缩短,导致v~C~=~O的红移和v~C~F~2的蓝移。由势能曲线可看出,A的势能比B高23kJ/mol,表明B比A稳定,升温能够发生A向B的转化。     

AB嵌段型均匀剂的分子设计与合成

介绍了AB嵌段型均匀剂的组成及原理,研究了一种新型AB嵌段型均匀剂的分子设计与合成,考察了链转移剂对特性粘度的影响以及引发剂对B段相对分子质量的影响。红外光谱谱图显示合成的均匀剂具有AB嵌段结构。应用试验表明,设计并合成制备的AB嵌段型均匀剂具有优良的不同胶相间的均化作用,提高了不同极性共用橡胶的力学性能。     

原子簇局部非定域分子轨道模型及其应用I.双氧桥双核钼(V)六配位配合物的电子光谱和电子结构

本文介绍了原子簇局部非定域分子轨道模型的处理要点。推出了一系列波长与Mo-Mo间距之间的关系式。并讨论了Mo-Mo金属键、磁性、稳定性及轨道特性和跃迁谱带之间的关系,计算结果与实测一致,并同SCF-MO计算进行了比较。     

斑蝥素衍生物的量子化学研究

在112种合成的斑蝥素衍生物中,N-羟基斑蝥胺(2)、N-甲基斑蝥胺(3)、N-乙基斑蝥胺(4)、N-烯丙基斑蝥胺(5)具有抗肝癌活性,且毒副作用很小。其中N-羟基斑蝥胺和N-甲基斑蝥胺已用于临床试验,疗效较好。关于斑蝥素衍生物化学结构与抗肝癌活性之间的关系,已有报道,但尚未从电子结构方面系统考察构效因素。本文用CNDO/2法对五个活性和三个非活性斑蝥素衍生物分子,进行了量子化学计算,以探讨药物的构效关系。     

点内电子-电子库仑作用会引起退相干么?

利用一个开放的多端Aharonov—Bohm(AB)装置研究了存在点内库仑作用时，电子通过量子点时的相干性．作者发现点内库仑作用不会引起任何退相干效应，即电子隧穿通过量子点是完全相干的．另外，作者还发现，在两端AB装置中，电导AB振荡的振幅非对称性来源于受限的结构和库仑作用两方面．因此，不能把振幅的非对称性和退相干过程联系起来．     

Giant persistent currents in quasiperiodic mesoscopic rings

Giant persistent currents that occur in quasiperiodic Thue–Morse array of mesoscopic rings are proposed. As the order of the system increases, the maximum persistent current increases exponentially. The giant persistent current in a system with higher order is greater than that in traditional structures. It is found that the maximum persistent current occurs in the ring near the middle position of the array. The persistent current is also proportional to the sharpness of the transport resonance, which is dependent on the width of the allowed band in the bandstructure. A rule to determine the occurrence energy of the giant persistent currents for a system with arbitrary order is also proposed.