Miyazaki Mitsuhiko, Chatterjee Kuntal, Hattori Kaori, Otsuka Remina, Ishiuchi Shun-Ichi, Dopfer Otto, Fujii Masaaki
Institut für Optik und Atomare Physik , Technische Universität Berlin , Hardenbergstrasse 36 , 10623 Berlin , Germany.
J Phys Chem A. 2019 Aug 15;123(32):6828-6839. doi: 10.1021/acs.jpca.9b04460. Epub 2019 Aug 1.
Infrared (IR) spectra of resorcinol (Rs)-Ar clusters ( = 1 and 2) have been measured in the neutral and cationic ground states (S and D) by IR dip and resonance-enhanced multiphoton ionization (REMPI)-IR spectroscopy. The OH stretching vibrations in S keep their frequency regardless of the number of Ar atoms and the conformation of the OH groups in Rs (rotamers RsI and RsII), demonstrating that the Ar atoms are attached to the aromatic π-ring (π-bound structure) in S. In the D state, the IR spectra of Rs-Ar reflect the difference in the Rs conformations (RsI and RsII). For = 1, the IR spectra of both rotamers are almost the same as those of the corresponding monomer cations, indicating that Ar ligands essentially remain π-bonded after ionization. In contrast, the IR spectra of Rs-Ar show hydrogen-bonded and free OH stretching vibrations, demonstrating that for a significant fraction of the clusters, the Ar atoms migrate from the π-bound site to the OH groups. The ionization-induced π → H migration yields are not unity for both rotamers RsI-Ar and RsII-Ar. This result is in sharp contrast to phenol-Ar, in which one of the Ar atoms migrates to the OH site with 100% yield. The mechanism leading to the nonunity yield in Rs-Ar is discussed in terms of the number of OH binding sites and Franck-Condon factors. The ionization excess energy dependence of the IR spectra of Rs-Ar and its Rs-Ar fragments is discussed in terms of the Ar binding energies estimated from the photoionization and photodissociation efficiency spectra.
通过红外偶极和共振增强多光子电离（REMPI）-红外光谱法，在中性和阳离子基态（S态和D态）下测量了间苯二酚（Rs）-Ar团簇（ = 1和2）的红外（IR）光谱。S态下的OH伸缩振动频率不受Ar原子数量以及Rs中OH基团构象（旋转异构体RsI和RsII）的影响，这表明Ar原子在S态下附着于芳香π环（π键合结构）。在D态下，Rs-Ar的红外光谱反映了Rs构象（RsI和RsII）的差异。对于 = 1，两种旋转异构体的红外光谱与相应单体阳离子的红外光谱几乎相同，表明Ar配体在电离后基本保持π键合。相比之下，Rs-Ar的红外光谱显示出氢键合和自由OH伸缩振动，这表明对于相当一部分团簇，Ar原子从π键合位点迁移到了OH基团上。对于旋转异构体RsI-Ar和RsII-Ar，电离诱导的π→H迁移产率均不为1。这一结果与苯酚-Ar形成鲜明对比，在苯酚-Ar中，一个Ar原子以100%的产率迁移到OH位点。从OH结合位点数量和弗兰克-康登因子的角度讨论了Rs-Ar中产率不为1的机制。根据从光电离和光解离效率光谱估计的Ar结合能，讨论了Rs-Ar及其Rs-Ar碎片的红外光谱对电离过剩能量的依赖性。
