The Tonfined Effect of the Size of Helically Chiral SWCNT on the Chiral Transition Reaction of Lys Molecules
The chiral transitionmechanism of two conformations of Lys molecules confined in the helically chiral SWCNT was studied by introducing the ONIOM methodsusing combination of quantum mechanics and molecular mechanics.The structural analysis shows that the smaller the diameter of the nanotube,the more obvious the molecular skeleton deformation of the lysine in the confinement region,the smaller the distance between the hydrogen atom on the chiral carbon and the nitrogen atom of the amino.Calculations of potential energy surface indicate that when two conformations of Lys molecules confined in the SWCNT(6,4),the Gibbs free energy barrier of the rate-determining step of the optical isomerization reaction are 194.72 and 170.08 kJ · mol-1,which are respectively generated by the transition states that the proton transferred from the chiral carbon to nitrogen,and the double protons collaboratively transferred from the chiral carbon to the amino nitrogen and from amino and carbonyl oxygen,which is obviously lower than that the Gibbs free energy barrier of the rate-determining step of bare reaction in the same channel,i.e.252.6 kJ · mol-1.The apparent energy barrier of the optical isomerization reaction of two conformations of Lys molecules confined in the SWCNT(6,4) are 160.00 and 178.59 kJ · mol-1,respectively.They confined in the SWCNT(7,4),the energy barrier of the rate-determining step of the optical isomerization reaction are 238.28 and 217.18 kJ · mol-1.They confined in the SWCNT(8,4),the energy barrier of the rate-determining step of the optical isomerization reaction are 253.00 and 250.11 kJ · mol-1.The results show that the smaller the pore size of the helically chiral SWNT,the better the confined catalysis of the chiral transition reaction of Lys molecules,and the easier the optical isomerization reaction of the conformation on of Lys molecules confined in SWCNT(6,4).
nanotubeLyschiral transitionONIOM methodsdensity functionaltransition state
NETL
NSTL
万方数据
维普
