Rearrangements of a Water Molecule in Both Directions between Two Hydrogen-Bonding Sites of 5-Hydroxyindole Cation: Experimental Determination of the Energy Threshold for the Rearrangement
Rearrangements of a Water Molecule in Both Directions between Two Hydrogen-Bonding Sites of 5-Hydroxyindole Cation: Experimental Determination of the Energy Threshold for the Rearrangement
复制标题
5-羟基吲哚阳离子两个氢键位点之间水分子的双向重排：重排能量阈值的实验测定
DOI：
10.1021/acs.jpca.5b12111
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发表时间：
2016
期刊：
影响因子：
2.9
通讯作者：
H. Sekiya
中科院分区：
文献类型：
--
作者：
T. Ikeda;K. Sakota;H. Sekiya
在气相中研究了水分子在5-羟基吲哚（5 HI）阳离子两个氢键（H-键）位点之间的双向重排。红外吸收光谱表明，5 HI（OH）-（H2O）1和5 HI（NH）-（H2O）1在SO状态下形成了两种结构异构体，即5 HI（OH）-（H2O）1和5 HI（NH）-（H2O）1。通过双色共振双光子电离（2C-R2 PI）产生的[5 HI-（H2O）1]+的红外光解离光谱表明，[5 HI（OH）-（H2O）1]+和[5 HI（NH）-（H2O）1]+共存于D 0态。[5 HI（NH）-（H2O）1]+在R2 PI之后通过5 HI（NH）-（H2O）1的S1-SO起源出现的现象可以通过[5 HI（NH）-（H2O）1]+异构化为[5 HI（OH）-（H2O）1]+来解释，这对应于水的重排。此外，当[5 HI-（H2O）1]+通过5 HI（OH）-（H2O）1的S1-S 0来源产生时，也观察到相反方向的异构化。由[5 HI（NH）-（H2O）1]+的绝热电离能确定了[5 HI（NH）-（H2O）1]+中水重排的能量阈值上限为2127 ± 30 cm-1。在能量阈值以上，[5 HI-（H2O）1]+中的水分子可能在5 HI+的两个优先氢键位点之间波动。
Rearrangements of a water molecule in both directions between two hydrogen-bonding (H-bonding) sites of the 5-hydroxyindole (5HI) cation was investigated in the gas phase. IR-dip spectra of jet-cooled 5HI-(H2O)1revealed that two structural isomers, 5HI(OH)-(H2O)1and 5HI(NH)-(H2O)1, in which a water molecule is bound to either the OH group or the NH group of 5HI, were formed in the S0state. The IR photodissociation spectrum of [5HI-(H2O)1]+generated by two-color resonant two-photon ionization (2C-R2PI) via the S1–S0origin of 5HI(NH)-(H2O)1clearly showed that [5HI(OH)-(H2O)1]+and [5HI(NH)-(H2O)1]+coexist in the D0state. The appearance of [5HI(OH)-(H2O)1]+after R2PI via the S1–S0origin of 5HI(NH)-(H2O)1is explained by isomerization of [5HI(NH)-(H2O)1]+to [5HI(OH)-(H2O)1]+, which corresponds to the rearrangement of the water. In addition, isomerization in the opposite direction was also observed when [5HI-(H2O)1]+was generated via the S1–S0origin of 5HI(OH)-(H2O)1. The upper limit of the energy threshold for the rearrangement of the water in [5HI(NH)-(H2O)1]+was experimentally determined to be 2127 ± 30 cm–1from the adiabatic ionization energy of 5HI(NH)-(H2O)1. Above the energy threshold, the water molecule in [5HI-(H2O)1]+may fluctuate between the two preferential H-bonding sites of 5HI+.