单重态[H,C,C,N]体系势能面的ab initio计算研究

An ab intio computational study on the potential energy surface of singlet [H,C,C,N] system

用ａｂｉｎｉｔｉｏ方法在ＱＣＩＳＤ（ｔ）／６—３１１＋＋Ｇ（３ｄｆ ２ｐ）∥ＭＰ２／６—３１１＋＋Ｇ（ｄ，ｐ）并包括零 点能（△ＺＰＶＥ）水平下计算得到了单重态[Ｈ，Ｃ，Ｃ，Ｎ］体系的势能面（ＰＥＳ）。在势能面上找到了[Ｈ，Ｃ， Ｃ，Ｎ］体系６个异构体和１１个过渡态，并用频率进行了验证．其中具有 ＣＣＮ三元环的 ＨＣ（ＣＮ）异构 体在势能面上具有最低能量，其次是ＨＣＣＮ和ＨＣＮＣ结构，能量分别比ＨＣ（ＣＮ）高３．３８和 １５．３５ｋｃａｌ／ｍｏｌ．基于体系的势能面，在单重态 ＨＣＣＮ异构体中，只有具有 ＨＮＣ三元环的异构体(ＨＮ）ＣＣ不具备动力学稳定性，这为实验检测及合成其５种异构体提供了理论依据．

The potential energy surface of singlet [H, C, C, N] system including six isomers and eleven transition states which have been proved by vibrational frequencies was investigated by ab initio method at QCISD(t)/6 ?311 + + G(3df, 2p)//MP2/6-3 11 + G(d, p) level of theory with zero-point ener-gy inclusion. On the PES, the isomer HC(CN) that has a CCN three-membered ring is found to be thermodynamically the most stable isomer followed by HCCN and HCNC at 3.38 and 15.35kcal/mol higher, respectively. Based on the PES, only(HN)CC that has a HNC three-membered ring is not kinetically stable. The computational results show the theoretical evidences for the experimental detec- tion and synthesis of five kinetically stable isomers.