铁原子与氮分子间的相互作用——单端位构型

用杂化密度泛函B3LYP方法在6-311+G(d)基组水平上研究了Fe 原子与N2分子相互作用的单端位构型的直线形和弯曲形两种结构的平衡几何结构、电子结构、轨道布局及红外光谱等性质. 计算结果表明, 由于强的σ-σ电子对互斥作用, 基组态4s²3d⁶的Fe原子不能与N2分子发生化学作用; 当Fe 原子呈现可与N2之间发生σ-π授予反馈作用的激发组态时, Fe 与N2分子之间可形成稳定的结构; 在得到的多个电子态中, 能量最低的是直线形的1³∑^-, 比Fe(a⁵D)和N2(¹∑⁺g )能量高21.6 kJ·mol-1, 同时存在几个能量相近的电子态, 如1³∏、1³Φ; 弯曲形都是不稳定态, 可能是连接直线形和单侧双配位构型的过渡态; 单端位构型产物相对于基态的反应物均是热力学不稳定的; 单端位构型中Fe对N2的活化作用很小, N—N 键长增加不超过7 pm.

Interaction of Iron Atom and Nitrogen Molecule——the End-on Linear and Bent Structures

Density functional theory (DFT) B3LYP calculations were performed on end-on linear and bent FeN2 structures using 6-311+G(d) basis sets. The geometric structures, bonding properties, natural electronic configuration, natural charges, and total spin densities were studied. The linear structure was more stable than the bent one. Lots of electronic states were investigated and compared with earlier calculations at high level ab initio molecular orbital and DFT methods. The lowest state was 1³∑- for L-FeN2 but its energy was 21.6 kJ·mol -1 higher than the ground state reactants Fe(a⁵D) and N2(1∑⁺g) by 21.6 kJ·mol-1. The results showed that the nitrogen molecule was activated very little by the excited states Fe atom, the bond length of N2 in L-FeN2 complex elongated less than 7 pm in all states, and adsorbed with ground state by the van der Waals interaction force.