Kang Do Hyung, Cho Kwang Hyun, Kim Jinwoo, Eun Han Jun, Rhee Young Min, Kim Sang Kyu
Department of Chemistry, KAIST, Daejeon 34141, Republic of Korea.
J Am Chem Soc. 2023 Nov 29;145(47):25824-25833. doi: 10.1021/jacs.3c10099. Epub 2023 Nov 16.
The nature of the electron-binding forces in the dipole-bound states (DBS) of anions is interrogated through experimental and theoretical means by investigating the autodetachment dynamics from DBS Feshbach resonances of -, -, and -bromophenoxide (BrPhO). Though the charge-dipole electrostatic potential has been widely regarded to be mainly responsible for the electron binding in DBS, the effect of nonclassical electron correlation has been conceived to be quite significant in terms of its static and/or dynamic contributions toward the binding of the excess electron to the neutral core. State-specific real-time autodetachment dynamics observed by picosecond time-resolved photoelectron velocity-map imaging spectroscopy reveal that the autodetachment processes from the DBS Feshbach resonances of BrPhO anions cannot indeed be rationalized by the conventional charge-dipole potential. Specifically, the autodetachment lifetime is drastically lengthened depending on differently positioned Br-substitution, and this rate change cannot be explained within the framework of Fermi's golden rule based on the charge-dipole assumption. High-level quantum chemical calculations with EOM-EA-CCSD, which intrinsically takes into account electron correlations, generate more reasonable predictions on the binding energies than density functional theory (DFT) calculations, and semiclassical quantum dynamics simulations based on the EOM-EA-CCSD data excellently predict the trend in the autodetachment rates. These findings illustrate that static and dynamic properties of the excess electron in the DBS are strongly influenced by correlation interactions among electrons in the nonvalence orbital of the dipole-bound electron and highly polarizable valence orbitals of the bromine atom, which, in turn, dictate the interesting chemical fate of exotic anion species.
通过研究溴苯氧基（BrPhO）的偶极束缚态（DBS）的自脱附动力学，采用实验和理论手段探究了阴离子偶极束缚态（DBS）中电子结合力的本质。尽管电荷 - 偶极静电势被广泛认为是DBS中电子结合的主要原因，但非经典电子关联效应在其对多余电子与中性核结合的静态和/或动态贡献方面被认为相当显著。通过皮秒时间分辨光电子速度映射成像光谱观察到的特定态实时自脱附动力学表明，BrPhO阴离子的DBS费什巴赫共振的自脱附过程确实不能用传统的电荷 - 偶极势来解释。具体而言，自脱附寿命根据Br取代位置的不同而大幅延长，并且这种速率变化无法在基于电荷 - 偶极假设的费米黄金规则框架内得到解释。使用EOM - EA - CCSD进行的高级量子化学计算本质上考虑了电子关联，与密度泛函理论（DFT）计算相比，对结合能产生了更合理的预测，并且基于EOM - EA - CCSD数据的半经典量子动力学模拟出色地预测了自脱附速率的趋势。这些发现表明，DBS中多余电子的静态和动态性质受到偶极束缚电子的非价轨道中的电子与溴原子的高极化价轨道之间的关联相互作用的强烈影响，这反过来又决定了奇异阴离子物种有趣的化学命运。
