Department of Chemistry, University of Georgia, Athens, Georgia 30602, United States.
J Phys Chem A. 2023 Jun 8;127(22):4822-4831. doi: 10.1021/acs.jpca.3c01790. Epub 2023 May 25.
Gas-phase ion-molecule complexes of silver cation with benzene or toluene are produced via laser vaporization in a pulsed supersonic expansion. These ions are mass-selected and photodissociated with tunable UV-visible lasers. In both cases, photodissociation produces the organic cation as the only fragment via a metal-to-ligand charge-transfer process. The wavelength dependence of the photodissociation produces electronic spectra of the charge-transfer process. Broad structureless spectra result from excitation to the repulsive wall of the charge-transfer excited states. Additional transitions are detected correlating to the forbidden S → D silver cation-based atomic resonance and to the HOMO-LUMO excitation on the benzene or toluene ligand. Transitions to these states produce the same molecular cation photofragments produced in the charge-transfer transitions, indicating an unanticipated excited-state curve-crossing mechanism. Spectra measured for these ions are compared to those for ions tagged with argon atoms. The presence of argon causes a significant shift on the energetic positions of these electronic transitions for both Ag(benzene) and Ag(toluene).
气相中银离子与苯或甲苯的离子-分子复合物是通过脉冲超音速膨胀中的激光汽化产生的。这些离子被质量选择，并通过可调谐的紫外可见激光进行光解。在这两种情况下，光解通过金属-配体电荷转移过程产生有机阳离子作为唯一的碎片。光解的波长依赖性产生了电荷转移过程的电子光谱。宽带无结构光谱是由激发到电荷转移激发态的排斥壁引起的。额外的跃迁被检测到与基于银阳离子的 S → D 原子共振以及苯或甲苯配体上的 HOMO-LUMO 激发相关联。这些状态的跃迁产生与电荷转移跃迁中产生的相同的分子阳离子光碎片，表明存在意外的激发态曲线交叉机制。测量这些离子的光谱与用氩原子标记的离子的光谱进行比较。氩的存在导致银（苯）和银（甲苯）的这些电子跃迁的能量位置发生显著位移。
