限域在扶手椅型SWBNNT内Lys分子手性转变的反应机理

采用量子力学与分子力学组合的ONIOM方法, 研究限域在扶手椅型单壁氮化硼纳米管(SWBNNT)内赖氨酸(Lys)分子手性转变的反应机理. 采用原子中心密度矩阵传播（ADMP)分子动力学方法, 研究Lys分子在SWBNNT(5,5)内手性转变反应通道入口与出口势能面上的动态反应路径, 给出中间体和产物的微观动态反应图像. 结果表明： 随着纳米管管径的减小, 限域其中的Lys分子骨架C原子间的键角明显增大； 手性C上的H与氨基N的距离逐渐变小; 在SWBNNT(5,5)内, 通过2个基元反应Lys分子实现了手性转变； 在SWBNNT(6,6)和SWBNNT(7,7)内, 通过3个和4个基元反应Lys分子实现了手性转变 ; 在SWBNNT(5,5)内, Lys分子手性转变反应决速步骤自由能垒降为最低值190.1 kJ/mol. 在 SWBNNT(7,7)内, 决速步骤能垒与裸反应基本相同.

Reaction Mechanism and Kinetics of Chiral Transition of Lysine Molecules Confined in Armchair SWBNNT

Using the ONIOM methods by combining quantum mechanics and molecular mechanics, we studied the reaction mechanism of the chiral transition of lysine (Lys) molecules conf ined in the armchair single walled boron nitride nanotube (SWBNNT). Using atom centered density matrix propagation (ADMP) molecular dynamics methods, we studied Lys molecules in the SWBNNT(5,5) dynamic reaction path in the inlet and outlet of the potential energy surface in chiral transition reaction channel, and gave images of the microscopic dynamic reaction of intermediates and products. The results show that with the decrease of diameter of nanotube, the bond angle between the skeletal carbon atoms of Lys molecules confined in nanotubes increases obviousl y, and the distance between H and amino N on chiral carbon gradually becomes sma ller. The chiral transition of Lys molecules is achieved by a two\|s tep elementary reaction in SWBNNT(5,5), whereas it is achieved by the three\|ste p and four\|step elementary reactions in SWBNNT(6,6) and SWBNNT(7,7), respective ly. The free energy barrier of the rate\|determining step of Lys molecule chiral transition reaction is reduced to a minimum value of 190.1 kJ/mol in SWCNT(5,5) . The energy barrier of the rate\|determining step is similar to that of bare reaction in SWBNNT(7,7).