He Wendi, Xue Ying, Zhang Hui, Tian Anmin, Wong Ning-Bew
Faculty of Chemistry, Sichuan University, Chengdu, Sichuan 610064, PR China.
J Phys Chem B. 2006 Jan 26;110(3):1416-22. doi: 10.1021/jp053328t.
Twelve tautomers of 2,4-dithiothymine are calculated at the MP2/6-31+G(d) level, and the most stable one is referred to the di-keto form (P12). Then four H-bonded complexes between P12 and water are optimized at the MP2/6-31+G(d) level of theory. The calculation of vibrational frequencies and natural bond orbital analysis are also carried out at the same level to investigate the hydrogen bonds involved in all the systems. Within all the four complexes, three types of hydrogen bonds are formed, in which the O-H...S and N-H...O bonds are the normal bonds with the X-H bond elongation and red shift of the corresponding stretch frequencies, while the C-H...O interaction is an improper, blue-shifting hydrogen bond accompanied with the contraction of the C-H bond and a blue shift of the C-H stretch frequency. The topological properties are investigated with the atoms-in-molecules (AIM) theory. The NMR chemical shielding for the isolated and the four monohydrated 2,4-dithiothymine are calculated using the "gauge-including atomic orbital" (GIAO) method. The 1H chemical shifts are influenced by the formation of hydrogen bonds.
在MP2/6-31+G(d)水平上计算了2,4-二硫代胸腺嘧啶的12种互变异构体，其中最稳定的一种为二酮形式（P12）。然后在MP2/6-31+G(d)理论水平上优化了P12与水之间的四种氢键复合物。在同一水平上还进行了振动频率计算和自然键轨道分析，以研究所有体系中涉及的氢键。在所有四种复合物中，形成了三种类型的氢键，其中O-H...S和N-H...O键是正常键，伴随着X-H键伸长和相应伸缩频率的红移，而C-H...O相互作用是一种反常的、蓝移的氢键，伴随着C-H键的收缩和C-H伸缩频率的蓝移。用分子中的原子（AIM）理论研究了拓扑性质。使用“含规范原子轨道”（GIAO）方法计算了孤立的和四种一水合2,4-二硫代胸腺嘧啶的NMR化学屏蔽。1H化学位移受氢键形成的影响。
