卤代氰基卡宾自由基XCCN(X=F，Cl，Br)的理论研究

Theoretical Investigation on Halocyanocarbene XCCN(X=F,Cl,Br)

在Cs对称性和ANO-S基组下,使用全活化空间自洽场方法(CASSCF),研究了卤代氰基卡宾自由基及其阴离子的低能电子激发态性质.为了进一步考虑电子的动态相关效应,采用多组态二级微扰理论(CASPT2)获得更加精确的能量值.计算结果表明,XCCN的基态是三重态.单重态和三重态的能隙差ΔES-T(kJ/mol):7.4(FCCN)<13.4(ClCCN)<16.6(BrCCN).计算得到,XCCN(X=F,Cl,Br)最低垂直激发能分别为408.3,385.4和345.2kJ/mol,这归因于π(a′)→nxy的电子跃迁;XCCN的电子亲和势分别为235.7,233.0和237.2kJ/mol,与HCCN相比,其电子亲和势变大.

Complete the calculations by means of the active space self-consistent field method（CASSCF） with ANO-S basis sets was performed on the ground and low-lying electronic excited states of halocyanocarbene XCCN and their anions, with X = F, Cl and Br. Our results show that XCCN have triplet X3A″ neutral ground states and the singlet-triplet energy gaps △ES-T （kJ/mol） follow this order： 7.4 （ FCCN ） 〈 13.4 （ ClCCN ） 〈 16. 6 （BrCCN）. The calculated most intensive vertical excitation energies of XaA″→23A″ transitions for FCCN, ClCCN, and BrCCN at 408.3, 385.4 and 345.2 kJ/mol, respectively, are mainly attributed to the π（a＇） →nxy transitions. The adiabatic electron affinities for XCCN are found to be 235.7, 233.0 and 237.2 kJ/mol, respectively. Compared with the results of HCCN, the electron affinities are enhanced.