电场对Ni3（dpa）4Cl2金属串配合物结构影响的理论研究

应用密度泛函UBP86方法对具有分子导线潜在应用性的金属串配合物Ni3(dpa)4Cl2进行研究,分析了外电场对配合物的几何构型和电子结构的影响.结果表明,零电场条件下存在沿着Ni63+轴及轴向配体Cl的Ni—Ni及Ni—Cl离域作用.沿金属轴Cl4→Cl5方向施加外电场,可使高电势端的Ni2—Cl4键长增大而Ni1—Ni2键长减小,低电势端的Ni3—Cl5键长减小而Ni1—Ni3键长增大;分子能量降低,偶极矩线性增大;HOMO与LUMO能隙减小,前线占据轨道分布向低电势方向移动且轨道能升高,空轨道分布则向高电势方向移动且轨道能降低,其中沿着金属轴方向离域的前线轨道分布及其轨道能随电场的变化尤为显著.在电场作用下,电荷分布发生改变,低电势端Cl5的负电荷向高电势端Cl4转移,但金属和桥联配体的电荷变化很小;同样,在电场作用下,配合物存在明显的结构变化和电子转移现象,呈现出类似导电过程中电子定向转移的变化规律.

Theoretical Studies on the Effect of Electric Field on the Structures of Metal String Complex Ni3(dpa) 4Cl2

As a potential molecular wire species,Ni3(dpa)4Cl2 complex with metal string structure was investigated theoretically by density functional theory UBP86 methods incorporating the external electric field along the Ni6+3 chain.The results show that there is delocalization throughout the Ni6+3 chain and axial ligands Cl.Under the effect of electric field,the distance of bond Ni2-Cl4 increases,distance of bond Ni1-Ni2 decreases,distance of bond Ni1-Ni3 increases and distance of bond Ni3-Cl5 decreases along the direction of electric field.With an increase of the electric field,the molecular energy and the HOMO-LUMO energy gap decrease but the dipole moment increases linearly.When the electric field enhances,the spatial distribution of frontier occupied orbitals moves to the negative potential side with the orbital energy increasing,while that of unoccupied orbitals changes oppositely.Particularly,the frontier orbital delocalized along the Ni6+3 chain is more sensitive to the electric field.Moreover,the application of electric field changes the charge distribution.The negative charge moves from Cl5 with low potential end towards Cl4 with high potential end.However,the charges of metals and dpa-ligands are almost unchanged.The variations of structure and electric charge seem to present a disciplinarian similar to directional movement of electrons in the electrical conduction process.