范德华体系以外配位化合物的自旋轨道耦合研究:决定^(2)P_(3/2)态进一步裂分的关键因素

Spin-Orbit Coupling in Molecular Complexes beyond van der Waals Regime:Key Factors for Further Splitting of ^(2)P_(3/2) Ground State

本文报道了一项联合光电子能谱和理论计算的研究,探索碘原子与氩原子、氢氟酸、甲酸/乙酸、甘氨酸/甲基化甘氨酸衍生物等分子结合形成的配位化合物中的自旋轨道耦合现象.L.I^(-)(L=甲酸/乙酸化合物的低温光电子谱都呈现了三个清晰分辨的波峰,标识了三个自旋轨道耦合态的存在:分别为相应中性化合物中的X(1/2)、A(3/2)和B(1/2)态.X和A态的间距△E_(XA)都为0.10eV,而X和B态的间距△E_(XB)则分别为0.98和0.97eV.本文测得的裂分间距值与先前报道的不同的L·I^(·)(L=氩原子、氢氟酸、甘氨酸和甲基化甘氨酸)的值进行了比较,从而得出了涵盖以范德华力和由弱至强的氢键等多样的分子间相互作用为主导的化合物的自旋轨道耦合裂分规律:尽管不同类型化合物的△E_(XB)比较相似,但△E_(XA)对于配体类型和相互作用类型极其敏感,其数值范围涵盖了从5meV到150meV的跨度.总体而言,实验测得的自旋轨道耦合裂分间距与通过量子化学计算所得数值高度吻合,表明了△E_(XA)的大小与中性化合物的分子间相互作用强度成正相关而与键长成反比.

We report a joint spectroscopic and theoretical study probing spin-orbit coupling(SOC)in a variety of molecular complexes between an iodine atom and a ligand(L)with L ranging from Ar,HF to formic/acetic acids,and glycine/N-methylated glycine derivatives.Cryogenic photoelectron spectroscopy of L·I^(–)(L=HCOOH,CH3COOH)reveals three distinct peaks,identified as three SOC states,denoted as X(1/2),A(3/2),and B(1/2)for the corresponding neutrals.The X and A separationΔE_(XA) is measured to be 0.10 eV for both,whereas the X and B gap ΔE_(XB) is 0.98 and 0.97 eV for formic and acetic acid,respectively.These new ΔE_(XA) values are compared with the previously reported values for the molecular complexes L·I^(•) with L=Ar,HF,glycine,and N-methylated glycines.All together these complexes encompass a diversity of intermolecular interactions,from van der Waals to weak and strong hydrogen bonding.While the ΔE_(XB) remains similar,the ΔE_(XA) is shown to be extremely sensitive to the type of ligands and interactions,spanning from 5 meV to 150 meV.High-level relativistic quantum calculations including explicit SOC formulism nicely reproduce all experimental SOC splitting.A direct correlation between the magnitude of ΔE_(XA) with the intermolecular interaction strength or bond distance of the neutral complexes-the stronger interaction(shorter bond length),the greater splitting,is established.