Chemistry and Biochemistry Department, Institute for Theoretical Chemistry, The University of Texas at Austin, TX 78712-0165, United States.
J Mol Graph Model. 2010 Jun;28(8):807-13. doi: 10.1016/j.jmgm.2010.02.006. Epub 2010 Feb 18.
Ab initio molecular orbital (MP2/6-311+G**//MP2/6-31G+G**) and hybrid-density functional theory (B3LYP/6-311+G**//MP2/6-311+G**) methods and NBO analysis were used to study the stereoelectronic interaction effects on the conformational properties of hydrogen peroxide (1), hydrogen disulfide (2) and hydrogen diselenide (3). The results showed that the Gibbs free energy difference (G(T)-G(S)) values at 298.15K and 1atm between the skew (S) and trans (T) conformations (DeltaG(T-S)) increase from compound 1 to compound 2 but decrease from compound 2 to compound 3. The C conformations of compounds 1-3 are less stable than their S and T conformations. Based on these results, the racemization processes of the axial symmetrical (C(2) symmetry) conformations of compounds 1-3 take place via their T conformations. Based on the optimized ground state geometries using the MP2/6-311+G** level of theory, the NBO analysis of donor-acceptor (bond-antibond) interactions revealed that the stabilization (resonance) energy associated with LP(2)M2-->sigma*(M3-H4) electronic delocalization for the S conformations of compounds 1-3 are 1.35, 5.94 and 4.68 kcal mol(-1), respectively. There is excellent agreement between the variations of the calculated DeltaG(T-S) and stabilization (resonance) energies associated with LP(2)M2-->sigma*(M3-H4) electronic delocalization for the S conformations of compounds 1-3. The correlations between resonance energies, orbital integrals, dipole moments, bond orders, structural parameters and conformational behaviors of compounds 1-3 have been investigated. Test were made of complete basis set methods (CBS-QB3, CBS-4 and CBS-Q), the first two gave results essentially indistinguishable from those we used, but the CBS-Q results were in disagreement with experimental and other theoretical results.
采用从头算分子轨道（MP2/6-311+G**//MP2/6-31G+G**）和杂化密度泛函理论（B3LYP/6-311+G**//MP2/6-311+G**）方法以及自然键轨道（NBO）分析研究了过氧化氢（1）、氢二硫化物（2）和氢二硒化物（3）分子的构象性质的立体电子相互作用效应。结果表明，在 298.15 K 和 1 atm 下，S 和 T 构象之间的吉布斯自由能差（G(T)-G(S))值（DeltaG(T-S))从化合物 1 增加到化合物 2，但从化合物 2 减少到化合物 3。化合物 1-3 的 C 构象比 S 和 T 构象不稳定。根据这些结果，化合物 1-3 的轴向对称（C(2)对称）构象的外消旋化过程通过它们的 T 构象发生。基于 MP2/6-311+G理论水平优化的基态几何形状，供体-受体（键-反键）相互作用的 NBO 分析表明，化合物 1-3 的 S 构象中 LP(2)M2-->sigma(M3-H4)电子离域的稳定（共振）能分别为 1.35、5.94 和 4.68 kcal mol(-1)。化合物 1-3 的 S 构象的计算 DeltaG(T-S)和 LP(2)M2-->sigma(M3-H4)电子离域的稳定（共振）能的变化之间存在极好的一致性。还研究了化合物 1-3 的共振能、轨道积分、偶极矩、键序、结构参数和构象行为之间的相关性。测试了完全基组方法（CBS-QB3、CBS-4 和 CBS-Q），前两种方法得到的结果与我们使用的结果基本相同，但 CBS-Q 的结果与实验和其他理论结果不一致。
