1, 2-二硒方酸气相酸性和芳香性的理论研究

在RHF/6-311G^*^*水平优化得到1,2-二硒方酸(3,4-二羟基-3-环丁烯-1,2-二硒酮)三种平面构象异构体的平衡几何构型。进一步用MP2(full)/6-311G^*//RHF/6-311G^*^*方法计算三种异构体的单点能量,发现ZZ型异构体是能量最低构象,且ZZ和ZE型能量非常接近。用优化的最稳定构象ZZ型异构体在RHF/6-311G^*^*//RHF/6-311G^*^*,RHF/6-311+G^*^*//RHF/6-311+G^*^*,MP2(full)/6-311+G^*^*//RHF/6-311+G^*^*和B3LYP/6-311+G^*^*//B3LYP/6-311+G^*^*水平计算其气相酸性[ΔGⅲ~(~2~9~8~K~)]和同键反应芳香性稳定化能(HASE)。用基团加和法(groupincrementapproach)在RHF/6-311+G^*^*//RHF/6-311+G^*^*和B3LYP/6-311+G^*^*//B3LYP/6-311+G^*^*水平计算其磁化率增量(Λ)。计算结果指出标题化合物的键长发生了平均化,同键反应芳香性稳定化能和磁化率增量均为负值,表明它具有芳香性,实现了标题化合物芳香性的几何、能量和磁性的判定。

Theoretical studies of the aromaticity and gas-phase acidity of 1, 2- diselenosquaric acid

The conformation, aromaticity and gas-phase acidity (free energy of deprotonation, ΔGⅲ) of 1, 2-diselenosquaric acid (3, 4-dihydroxy-3- cyclubutene-1, 2-diselenone) were calculated at the SCF and MP2 and B3LYP levels using 6-311G(d, p) and 6-311+G(d, p) basis sets. The global minimum found on the potential energy surface of 1, 2- diselenosquaric acid presents a planar conformation. The ZZ isomer was found to be the most stable of the three planar conformers. The homodesmotic reaction aromatic stabilization energy (HASE) and magnetic susceptibility exaltation (Λ) were also computed by using the SCF-CSGT (Continues Set of Gauge Transformations) (IGAIM, a slight variation on CSGT) and B3LYP-CSGT (IGIAM) methods at the 6- 311+G(d, p) level. The calculated HASE and Λ were more negative values, indicating that 1, 2-diselenosqaric acid is aromatic. Thus the titled compound fulfills the geometrical, energetic and magnetic criteria of aromaticity. The most reliable theoretical gas-phase acidity are ΔGⅲ ~1~(~2~9~8~K~)=1271.5kJ/mol and ΔGⅲ ~2~ (~2~9~8~K~)=1619.6kJ/mol.