Borane Adducts of Aromatic Phosphorus Heterocycles: Synthesis,Crystallographic Characterization and Reactivity of a Phosphinine-B(C6F5)3 Lewis Pair

A phosphinine-borane adduct of a Me₃Si-functionalized phosphinine and the Lewis acid B(C₆F₅)₃ has been synthesized and characterized crystallographically for the first time. The reaction strongly depends on the nature of the substituents in the α-position of the phosphorus heterocycle. In contrast, the reaction of B₂H₆ with various substituted phosphinines leads to an equilibrium between the starting materials and the phosphinine–borane adducts that is determined by the Lewis basicity of the phosphinine. The novel phosphinine borane adduct ( 6 -B(C₆F₅)₃) shows rapid and facile insertion and [4+2] cycloaddition reactivity towards phenylacetylene. A hitherto unknown dihydro-1-phosphabarrelene is formed with styrene. The reaction with an ester provides a new, facile and selective route to 1-R-phosphininium salts. These salts then undergo a [4+2] cycloaddition in the presence of Me₃Si−C≡CH and styrene to cleanly form unprecedented derivatives of 1-R-phosphabarrelenium salts.     

·OH自由基引发CH3SSCH3•+自由基裂解反应机理的理论研究

采用UωB97X-D/6-311+G^**方法, 研究了气相、 甲苯和水中OH自由基(·OH)引发CH₃SSCH₃自由基阳离子(CH₃SSC{\mathrm{H}}_{\mathrm{3}}^{?}⁺, DMDS^?+)裂解的反应机理, 并讨论了溶剂效应对反应的影响. 结果表明, ·OH和DMDS^·+首先形成自由基耦合产物CH₃S(OH)SCH₃⁺(R1)和氢提取产物复合物[CH₂=SSCH₃+H₂O]⁺(R2); 随后R1裂解直接发生 S—S键断裂协同质子转移, 而R2裂解依次发生构象变化、 C=S键亲碳加成和S—S键断裂协同质子转移. 去质子化的裂解产物为CH₃SOH, CH₂=S和HSCH₂OH. 甲苯略微降低了裂解反应速控步骤的自由能垒. 水溶剂有利于R1裂解, 但不利于R2裂解, 尤其是单个水分子参与反应. 在气相、 甲苯和水中, 以·OH和DMDS^·+为初始反应物, 虽然速控步骤的自由能垒为167.6~202.8 kJ/mol, 但裂解反应均是放热反应(?154.3~?31.4 kJ/mol).     

Sc3C2@C80与[12]CPP纳米环之间非共价相互作用的理论研究

金属富勒烯嵌套于纳米环内形成主客体系, 二者产生的主客体作用可诱导内部金属团簇的取向, 影响分子的电子结构等性质. 本文基于密度泛函理论(DFT)计算, 对碳纳米环[12]CPP(CPP=环苯撑, 主体分子)与金属富勒烯Sc₃C₂@C₈₀(客体分子)形成的主客体配合物的结构和性质进行了研究. 计算结果表明, 在最稳定构型中, [12]CPP呈现椭圆形, Sc₃C₂@C₈₀与[12]CPP的质心不再重合. Sc₃C₂@C₈₀在[12]CPP内旋转对构型总体能量影响仅为13.51 kJ/mol. [12]CPP向Sc₃C₂@C₈₀转移了0.03 e, 主客体分子之间存在弱相互作用. 对二者相互作用的分析结果表明, 色散作用在弱相互作用中占主导地位.     

The Charge Transfer Complex between 2, 3-diamino-5-bromopyridine and Chloranilic acid: Preparation,Spectroscopic Characterization,DNA binding,and DFT/PCM analysis

A charge transfer hydrogen bonded complex was prepared and experimentally explored in an acetonitrile (ACN) medium between the proton acceptor (electron donor) 2, 3-Diamino-5-bromopyridine and the proton donor (electron acceptor) chloranilic acid. The stoichiometry of the charge transfer complex is 1:1. The Benesi-Hildebrand equation is used to calculate the molar absorptivity (ε_CT), association constant (K_CT) and other spectroscopic physical characteristics. The solid compound was synthesized and studied using several spectroscopic methods. The presence of charge and proton transfers in the resultant complex was supported by ¹H NMR, FT-IR and SEM-EDX investigations. The complex DNA binding ability was investigated using electron absorption spectroscopy, and the CT complex binding mechanism is intercalative. The intrinsic binding constant (K_b) value is 5.2 × 10⁶M?1. The good binding affinity of the CT complex makes it potentially suitable for usage as a pharmaceutical in the future. Molecular docking calculations have been performed between CT complex and DNA (ID = 1BNA) to study the CT-DNA interaction theoretically. To corroborate the experimental findings, calculations based on DFT were carried out in the gas and PCM analysis where the existence of charge and hydrogen transfers. Finally, good agreement between experimental and theoretical computations was observed confirming that the basis set used is appropriate for the system under examination.     

二甲双胍化学反应性的密度泛函理论研究及实验研究

二甲双胍(MET)是一个非常优良的降血糖药,一直是治疗II型糖尿病(T2DM)的首选药物,但其脂溶性较差,也存在引起胃肠道不适等副作用,对其结构修饰和衍生化,特别是将其研制成前药(Prodrug)具有一定的临床意义。为了探明二甲双胍化学反应的性能特点,本文基于密度泛函理论（DFT）开展了二甲双胍的化学内禀性质研究,包括各种可能互变异构体的单点能和量子化学反应性指数。此外,还对各异构体互变过程的过渡态以及它们的反应路径进行了研究。在此基础上,本文还对二甲双胍与亲电试剂的化学反应机理进行了初探,并用化学合成反应来验证,从而让我们能够从理论上弄清楚二甲双胍化学反应的特殊性质。     

铀酰与羧酸和肟基类配体相互作用的理论研究

深入了解各种功能基团与铀酰离子的络合行为有助于设计和开发高效海水提铀吸附剂. 本工作通过密度泛函理论(DFT)方法系统地研究了两种典型铀酰络合配体吡啶-2,6-二羧酸(H₂DPA)和戊二酰偕亚胺二肟(H₂A)与铀酰离子及碳酸根离子形成的配合物的结构、成键性质以及热力学稳定性. 研究结果表明, 所有配合物中, 配体与铀酰离子之间具有不同强度的共价相互作用. 由于H₂A配位时发生了质子重排, 而且配体的解离能较高, 使其更难与[UO₂(CO₃)₃]^4-发生取代反应, 因此H₂DPA配体是海水提铀中一种潜在的有效配体. 本工作的相关研究结果为海水提铀中高效吸附基团的设计和开发提供了理论线索.     

纳米孔缺陷导致单层黑磷电荷局域极大抑制非辐射电子-空穴复合的时域模拟

通常认为缺陷加速黑磷的非辐射电子-空穴复合,阻碍器件性能的持续提高。实验打破了这一认识。采用含时密度泛函理论结合非绝热分子动力学,我们发现P-P伸缩振动驱动非辐射电子-空穴复合,使纳米孔修饰的单层黑磷的激发态寿命比完美体系延长了约5.5倍。这主要归因于三个因素。一,纳米孔结构不但没有在禁带中引入深能级缺陷,而且由于价带顶下移使带隙增加了0.22 eV。二,除了带隙增加,纳米孔减小了电子和空穴波函数重叠,并抑制了原子核热运动,从而使非绝热耦合降低至完美体系的约1/2。三,退相干时间比完美体系延长了1.5倍。前两个因素战胜了第三个因素,使纳米孔结构激发态寿命延长至2.74 ns,而其在完美体系中约为480 ps。我们的研究表明可以制造合理数量和形貌的缺陷,如纳米孔,降低黑磷非辐射电子-空穴复合,提高光电器件效率。这一研究对于理解和调控黑磷和其它二维材料的激发态性质有重要意义。