Department of Chemistry, Kyung Hee University, 1 Seochun-dong, Giheung-Gu, Yongin-si, Gyeonggi-do, 449-701, Korea.
J Phys Chem A. 2010 Mar 18;114(10):3403-10. doi: 10.1021/jp910533m.
Variational transition state theory calculations including multidimensional tunneling (VTST/MT) for excited-state tautomerization in the 1:1 7-azaindole:H(2)O complex were performed. Electronic structures and energies for reactant, product, transition state, and potential energy curves along the reaction coordinate were computed at the CASSCF(10,9)/6-31G(d,p) level of theory. The potential energies were corrected by second-order multireference perturbation theory to take the dynamic electron correlation into consideration. The final potential energy curves along the reaction coordinate were generated at the MRPT2//CASSCF(10,9)/6-31G(d,p) level. Two protons in the excited-state tautomerization are transferred concertedly, albeit asynchronously. The position of the variational transition state is very different from the conventional transition state, and is highly dependent on isotopic substitution. Rate constants were calculated using VTST/MT, and were on the order of 10(-6) s(-1) at room temperature. The HH/DD kinetic isotope effects are consistent with experimental observations; consideration of both tunneling and variational effects was essential to predict the experimental values correctly.
对 1:1 7-氮杂吲哚：H(2)O 复合物中激发态互变异构的变分过渡态理论计算包括多维隧道（VTST/MT）进行了计算。在 CASSCF(10,9)/6-31G(d,p)理论水平上计算了反应物、产物、过渡态和沿反应坐标的势能曲线的电子结构和能量。通过二级多参考微扰理论对势能进行了修正，以考虑动态电子相关。最后在 MRPT2//CASSCF(10,9)/6-31G(d,p)水平上生成了沿反应坐标的最终势能曲线。尽管在激发态互变异构中两个质子是协同转移的，但却是异步的。变分过渡态的位置与传统过渡态非常不同，并且高度依赖于同位素取代。使用 VTST/MT 计算了速率常数，在室温下约为 10(-6) s(-1)。HH/DD 动力学同位素效应与实验观察一致；考虑隧道和变分效应对于正确预测实验值至关重要。
