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在B3LYP/ 6- 311+G 水平上 ,对Na -呋喃体系可能存在的弱相互作用复合物进行了全自由度能量梯度优化 ,发现了Na -呋喃体系存在两个能量极小结构A、B ,其中 ,结构A是Na原子的 3s1电子直接和呋喃杂环体系中的所有重原子的共轭大π体系相互偶合 ,形成一个具有Cs 对称性的金属有机复合物 ;而结构B为Na原子的 3s1电子主要通过杂原子O和杂环上原有的五中心六电子大π体系形成一个新的平面六中心七电子大π体系 ,具有C2V对称性。结构B较结构A稳定 3.4 0kJ/mol。结构A中的Na -O键长为 0 .38nm ,∠COC为 10 6.9° ,由于金属Na对呋喃杂环的作用使整个分子平面变形 ,C1、C2、C3、C4在同一个平面内 ,而O5则稍微翘离平面且O5原子距离由C1、C2、C3、C4组成的平面的垂直距离约为 0 .0 35nm。结构B中Na -O键长为 0 .2 6nm ,∠COC为 10 6.8° ,金属Na原子和杂环中所有的原子在同一个平面内。并在MP2和B3LYP水平下 ,用 6- 311+G 基组精确计算了最稳定结构B的结合能为ΔE =4 .5～ 5.1kJ/mol。
At the level of B3LYP / 6- 311 + G, the full - degree - of - freedom energy gradient optimization of weak interaction complexes in Na - furan system was found. It was found that there are two small energy structures A, B, Among them, the structure A is a Na atom 3s1 electron direct and furan heterocyclic system of heavy atoms conjugate large π system coupled with each other to form a Cs symmetry of the metal-organic complexes; and Structure B Na atom 3s1 The electron forms a new planar six-center, seven-electron system with symmetry C2V mainly through heteroatoms O and the original five-center six-electron system. Structure B is more stable than structure A 3.4 0 kJ / mol. In the structure A, the Na-O bond length is 0.38 nm and the ∠COC is 10 6.9 °. Since the effect of the metal Na on the furan heterocycle deforms the entire molecular plane, C1, C2, C3 and C4 are in the same plane, and O5 is slightly off the plane and the O5 atom’s vertical distance from the plane consisting of C1, C2, C3, C4 is about 0.0535 nm. In Structure B, the Na-O bond length is 0.226 nm and the ∠COC is 10 6.8 °. The metal Na atoms and all the atoms in the heterocycle are in the same plane. And at MP2 and B3LYP levels, the binding energy of the most stable structure B was calculated as ΔE = 4.5-1.5 kJ / mol using the 6- 311 + G basis set.