亚累积烯基卡宾的两个最低能态

本文用量子化学从头计算方法对一些不饱和卡宾进行了研究。采用STO—3G极小基组,对不饱和卡宾H_2C=C=C:,F_2C=C=C:,Li_2C=C=C:,和H_2C=C=C=C:的两个最低能态的几何构型进行了能量梯度法优化。选用3—21G价层分裂基对STC—3G优化几何构型下的分子进行了RHF计算,得到了两个最低能态的能隙。结果预言了不饱和卡宾类X_2C=C=C:和H_2C=C=C=C:的基态是单重态。X原子或基团的电负性影响分子的几何构型和基态的稳定性。亚累积烯基长度对分子构型及能隙的影响较X的电负性影响要小。

The Two Lowest Energy States of Cumulidenecarbenes

Ab initio molecular orbital calculations are carried out on some cumulidenecarbenes. The two lowest energy states of cumulene carbenes, H_2C=C=C:, F_2C=C=C:, Li_2C=C=C:, and H_2C=C=C=C: are studied at the restricted Hartree-Fock (RHF) level of approximation. The geometries are optimized with the analytical energy gradient scheme at the level of STO-3G mini-basis sets. 3-21G calculations are made for the molecules whose geometries are optimized above. It gives the energy gaps between the lowest energy states and the first excited states. The results show that the ground states of unsaturated carbenes X_2(?)C(?)_n C: are singlet. The electrone- gtivities of atom or group X affect the geometries and the the stability of the molecules on the ground states. The increase of carbon atom affluences lettle than the electronegtivity of X does.