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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。
In this paper, a number of unsaturated carbenes have been studied by ab initio method of quantum chemistry. Using the STO-3G minimal basic set, the two lowest energy states of unsaturated carbene H_2C = C = C:, F_2C = C = C:, Li_2C = C = C :, and H_2C = C = C = C: The geometric configuration is optimized by energy gradient method. The 3-21G valence splitting group was used to calculate the RHF of the molecules under the optimized STC-3G geometry. The energy gaps of the two lowest states were obtained. The results predict that the ground states of unsaturated carbene X_2C = C = C: and H_2C = C = C = C: are singlet states. Electronegativity of X atoms or groups affects the geometry of the molecule and the stability of the ground state. The effect of sub-cumulative alkenyl length on molecular configuration and energy gap is less than that of X.