Colley Jason E, Dynak Nathan J, Blais John R C, Duncan Michael A
Department of Chemistry, University of Georgia, Athens, Georgia 30602, United States.
J Phys Chem A. 2023 Feb 9;127(5):1244-1251. doi: 10.1021/acs.jpca.2c08456. Epub 2023 Jan 26.
Tunable laser photodissociation spectroscopy in the 700-400 nm region and photofragment imaging experiments are employed to investigate the Fe(acetylene) ion-molecule complex. At energies above a threshold at 679 nm, continuous dissociation is detected throughout the visible wavelength region, with regions of broad structure. Comparison to the spectrum predicted by time-dependent density functional theory (TD-DFT) indicates that the complex has a quartet ground state. The dissociation threshold for Fe(acetylene) at 679 nm provides the dissociation energy on the quartet potential energy surface. Correction for the atomic quartet-sextet spin state energy difference provides an adiabatic dissociation energy of 36.8 ± 0.2 kcal/mol. Photofragment imaging of the Fe photoproduct produced at 603.5 nm produces significant kinetic energy release (KER). The photon energy and the maximum value of the KER provide an upper limit on the dissociation energy of ≤ 34.6 ± 3.2 kcal/mol. The dissociation energies determined from the spectroscopy and photofragment imaging experiments agree nicely with the value determined previously by collision-induced dissociation (38.0 ± 2.6 kcal/mol). However, both values are significantly lower than those produced by computational chemistry at the DFT level using different functionals recommended for transition-metal chemistry.
利用700 - 400 nm区域的可调谐激光光解离光谱和光碎片成像实验来研究铁（乙炔）离子 - 分子复合物。在高于679 nm阈值的能量下，在整个可见波长区域检测到连续解离，伴有宽结构区域。与时间相关密度泛函理论（TD-DFT）预测的光谱进行比较表明，该复合物具有四重基态。679 nm处铁（乙炔）的解离阈值给出了四重势能面上的解离能。对原子四重态 - 六重态自旋态能量差进行校正后，得到绝热解离能为36.8±0.2 kcal/mol。对603.5 nm处产生的铁光产物进行光碎片成像产生了显著的动能释放（KER）。光子能量和KER的最大值给出了解离能的上限≤34.6±3.2 kcal/mol。由光谱和光碎片成像实验确定的解离能与先前通过碰撞诱导解离确定的值（38.0±2.6 kcal/mol）非常吻合。然而，这两个值都明显低于使用推荐用于过渡金属化学的不同泛函在DFT水平下由计算化学得出的值。
