采用组合的量子化学ONIOM(our own n-layered integrated molecule orbit and molecule mechanics)(B3LYP/6-31++G(d,p):UFF)方法,研究了限域在SWBNNT(9,9)内α-丙氨酸的分子结构和手性转变通道.为得到高水平的能量,在ONIOM(B3LYP/6-311...采用组合的量子化学ONIOM(our own n-layered integrated molecule orbit and molecule mechanics)(B3LYP/6-31++G(d,p):UFF)方法,研究了限域在SWBNNT(9,9)内α-丙氨酸的分子结构和手性转变通道.为得到高水平的能量,在ONIOM(B3LYP/6-311++G(3df,3pd):UFF)水平,计算了各个包结物的单点能.分子结构分析表明:与单体α-丙氨酸相比,受限在SWBNNT(9,9)内时,骨架碳氮原子间的键长不同程度地缩短,骨架碳原子的键角及骨架碳氮原子的二面角略有增大.反应路径研究发现:α-丙氨酸分子在SWBNNT(9,9)内的手性转变有两条同单体情况大致相同的反应通道,不存在单体情况的含有羰基H和甲基H协同转移过程的反应通道.手性转变反应过程的势能面计算发现:与单体α-丙氨酸手性转变反应过程的主要能垒相比较,在纸外面的氢从手性碳直接到羰基氧的过渡态产生的能垒,从326.5kJ·mol-1降到319.7kJ·mol-1;氢首先在羧基内转移,而后手性碳的氢在纸面外转移到羰基,这两个过程的能垒从198.0kJ·mol-1和320.3kJ·mol-1降到135.5kJ·mol-1和302.7kJ·mol-1.结果表明:限域在SWBNNT(9,9)内的α-丙氨酸,其手性转变过程中不同的氢转移反应能垒被不同程度地降低.展开更多
A Michael addition is usually taken as a base-catalysed reaction. However, our synthesized 2-（quinolin-2-ylmethylene） malonic acid （QMA） as a Michael-type thiol fluorescent probe is acid-active in its sensing reac...A Michael addition is usually taken as a base-catalysed reaction. However, our synthesized 2-（quinolin-2-ylmethylene） malonic acid （QMA） as a Michael-type thiol fluorescent probe is acid-active in its sensing reaction. In this work, based on theoretic calculation and experimental study on 7-hydroxy-2-（quinolin-2-ylmethylene） malonic acid, we demonstrated that QMA as a Michael acceptor is acid-activatable, i.e., it works only in solutions at pH〈7, and the lower the pH of solutions is, the higher reactivity QMA has. In alkaline solution, the malonate QMA[-2H＋]2- cannot react with both RSand RSH. In contrast, 2-（quinolin-2- ylmethylene） malonic ester （QME）, the ester of QMA, reveal a contrary pH effect on its sensing reaction, that is, it can sense thiols in alkaline solutions but not in acidic solutions, like a normal base-catalysed Michael addition. The values of activation enthalpies from theoretic calculation support the above sensing behavior of two probes under different pH conditions. In acidic solutions, the protonated QMA is more highly reactive towards electrophilic attack over its other ionized states in neutral and alkaline solutions, and so can react with lowly reactive RSH. In contrast, there is a big energy barrier in the interaction of QME with RSH （acidic solutions）, and the reaction of QME with the highly reactive nucleophile RS- is a low activation energy process （in alkaline solutions）. Theoretic calculation reveals that the sensing reaction of QMA undergoes a 1,4-addition process with neutral thiols （RSH）, and a 1,2-addition pathway for the sensing reaction of QME with RS-. Therefore, the sensing reaction of QMA is an acid-catalysed Michael addition via a 1,4-addition, and a normal base-catalysed Michael addition via a 1,2-addition.展开更多
本文回顾了现代密度泛函理论的基础,着重评述了XYG3型双杂化(XYG3 type of doubly hybrid,xDH)泛函的最新进展,解析能量梯度的实现.XYG3是首个依照绝热途径理论建立的双杂化泛函,在具体实现上具有独特的构架.该类型泛函利用常用泛函(如B...本文回顾了现代密度泛函理论的基础,着重评述了XYG3型双杂化(XYG3 type of doubly hybrid,xDH)泛函的最新进展,解析能量梯度的实现.XYG3是首个依照绝热途径理论建立的双杂化泛函,在具体实现上具有独特的构架.该类型泛函利用常用泛函(如B3LYP或PBE0等)作母泛函来进行自洽计算,以期获得更好的密度和轨道,然后将所得到的轨道和密度信息带入到xDH泛函中以得到最终能量.由于自洽泛函和最终能量泛函不同,因而在计算解析能量梯度时需要求解耦合微扰Kohn-Sham方程.在此基础上,还评述了xDH泛函在能量,尤其是构型优化方面的具体表现.测试的构型集包括以共价键键合的分子和非键相互作用体系的平衡结构,以及反应过渡态结构.结果表明,xDH双杂化泛函总体上给出了比母泛函更好的能量和几何构型.展开更多
文摘采用组合的量子化学ONIOM(our own n-layered integrated molecule orbit and molecule mechanics)(B3LYP/6-31++G(d,p):UFF)方法,研究了限域在SWBNNT(9,9)内α-丙氨酸的分子结构和手性转变通道.为得到高水平的能量,在ONIOM(B3LYP/6-311++G(3df,3pd):UFF)水平,计算了各个包结物的单点能.分子结构分析表明:与单体α-丙氨酸相比,受限在SWBNNT(9,9)内时,骨架碳氮原子间的键长不同程度地缩短,骨架碳原子的键角及骨架碳氮原子的二面角略有增大.反应路径研究发现:α-丙氨酸分子在SWBNNT(9,9)内的手性转变有两条同单体情况大致相同的反应通道,不存在单体情况的含有羰基H和甲基H协同转移过程的反应通道.手性转变反应过程的势能面计算发现:与单体α-丙氨酸手性转变反应过程的主要能垒相比较,在纸外面的氢从手性碳直接到羰基氧的过渡态产生的能垒,从326.5kJ·mol-1降到319.7kJ·mol-1;氢首先在羧基内转移,而后手性碳的氢在纸面外转移到羰基,这两个过程的能垒从198.0kJ·mol-1和320.3kJ·mol-1降到135.5kJ·mol-1和302.7kJ·mol-1.结果表明:限域在SWBNNT(9,9)内的α-丙氨酸,其手性转变过程中不同的氢转移反应能垒被不同程度地降低.
基金This work is supported by the National Natural Science Foundation of China （No.21272224）, the Open Research Fund of State Key Laboratory of Physical Chemistry of Solid Surfaces, Xiamen University （No.201410）, and the Open Research Fund of Key Laboratory of Advanced Scientific Computation, Xihua University （No.szjj2013-024）.
文摘A Michael addition is usually taken as a base-catalysed reaction. However, our synthesized 2-（quinolin-2-ylmethylene） malonic acid （QMA） as a Michael-type thiol fluorescent probe is acid-active in its sensing reaction. In this work, based on theoretic calculation and experimental study on 7-hydroxy-2-（quinolin-2-ylmethylene） malonic acid, we demonstrated that QMA as a Michael acceptor is acid-activatable, i.e., it works only in solutions at pH〈7, and the lower the pH of solutions is, the higher reactivity QMA has. In alkaline solution, the malonate QMA[-2H＋]2- cannot react with both RSand RSH. In contrast, 2-（quinolin-2- ylmethylene） malonic ester （QME）, the ester of QMA, reveal a contrary pH effect on its sensing reaction, that is, it can sense thiols in alkaline solutions but not in acidic solutions, like a normal base-catalysed Michael addition. The values of activation enthalpies from theoretic calculation support the above sensing behavior of two probes under different pH conditions. In acidic solutions, the protonated QMA is more highly reactive towards electrophilic attack over its other ionized states in neutral and alkaline solutions, and so can react with lowly reactive RSH. In contrast, there is a big energy barrier in the interaction of QME with RSH （acidic solutions）, and the reaction of QME with the highly reactive nucleophile RS- is a low activation energy process （in alkaline solutions）. Theoretic calculation reveals that the sensing reaction of QMA undergoes a 1,4-addition process with neutral thiols （RSH）, and a 1,2-addition pathway for the sensing reaction of QME with RS-. Therefore, the sensing reaction of QMA is an acid-catalysed Michael addition via a 1,4-addition, and a normal base-catalysed Michael addition via a 1,2-addition.
文摘本文回顾了现代密度泛函理论的基础,着重评述了XYG3型双杂化(XYG3 type of doubly hybrid,xDH)泛函的最新进展,解析能量梯度的实现.XYG3是首个依照绝热途径理论建立的双杂化泛函,在具体实现上具有独特的构架.该类型泛函利用常用泛函(如B3LYP或PBE0等)作母泛函来进行自洽计算,以期获得更好的密度和轨道,然后将所得到的轨道和密度信息带入到xDH泛函中以得到最终能量.由于自洽泛函和最终能量泛函不同,因而在计算解析能量梯度时需要求解耦合微扰Kohn-Sham方程.在此基础上,还评述了xDH泛函在能量,尤其是构型优化方面的具体表现.测试的构型集包括以共价键键合的分子和非键相互作用体系的平衡结构,以及反应过渡态结构.结果表明,xDH双杂化泛函总体上给出了比母泛函更好的能量和几何构型.
