3,4-二硒方酸芳香性和气相酸性的理论研究

Theoretical Studies on the Aromaticity and Gas phase Acidity of 3,4-Diselenosquaric acid

在ＲＨＦ／６－３１１Ｇ水平优化得到３，４－二硒方酸（３，４－二氢硒基－３－环丁烯－１，２－二酮）３ 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（ΔＧ°）和同键反应芳香性稳定化能（ＨＡＳＥ）。用基团加和法（ｇｒｏｕｐ ｉｎｃｒｅｍ ｅｎｔ ａｐ－ｐｒｏａｃｈ ） 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。

The conformation, aromaticity and gas phase acidity(free energy of deprotonation, ΔG ° ) of 3,4 diselenosquaric acid (3,4 diselenyl 3 cyclubutene 1,2 dione) 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 much negative magnitudes, indicating that 3,4 diselenosqaric acid is aromatic. Thus the title compound fulfilled the geometrical, energetic and magnetic criteria of aromaticity. The most reliable theoretical gas phase acidity are ΔG ° 1(298k) =1280.7kJ/mol and ΔG ° 2(298k) =1665.7 kJ/mol.\;