Reactivity and infrared spectroscopy of gaseous hydrated trivalent metal ions
Reactivity and infrared spectroscopy of gaseous hydrated trivalent metal ions
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DOI：
10.1021/ja801894d
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发表时间：
2008-07-16
影响因子：
15
通讯作者：
Williams, Evan R.
中科院分区：
文献类型：
--
作者：
Bush, Matthew F.;Saykally, Richard J.;Williams, Evan R.
采用电喷雾电离法制备了含钇和所有天然丰富的镧系金属的水合三价稀土金属离子，并利用黑体红外辐射解离（BIRD）和红外作用光谱对这些含17-21水分子的离子的结构和反应性进行了探测。在低能量激活条件下，BIRD的解离途径发生了一个突变，从单个中性水分子的独家损失到通过电荷分离过程的独家损失小质子化水团簇。这种转变发生在一个狭窄的簇大小范围内，每个金属离子只有几个水分子的差异。这两种解离速率相等时的有效转换大小取决于金属离子的同质性，与分离金属的第三电离能相关性较差，但与三价金属离子在体积水溶液中的水解常数相关性较好。这些离子在接近周转量大小的簇大小处的红外作用光谱在很大程度上独立于三价金属离子的特定身份，这表明我们实验中存在的离子结构的任何差异都是微妙的。
Hydrated trivalent rare earth metal ions containing yttrium and all naturally abundant lanthanide metals are formed using electrospray ionization, and the structures and reactivities of these ions containing 17-21 water molecules are probed using blackbody infrared radiative dissociation (BIRD) and infrared action spectroscopy. With the low-energy activation conditions of BIRD, there is an abrupt transition in the dissociation pathway from the exclusive loss of a single neutral water molecule to the exclusive loss of a small protonated water cluster via a charge-separation process. This transition occurs over a narrow range of cluster sizes that differs by only a few water molecules for each metal ion. The effective turnover size at which these two dissociation rates become equal depends on metal ion identity and is poorly correlated with the third ionization energies of the isolated metals but is well correlated with the hydrolysis constants of the trivalent metal ions in bulk aqueous solution. Infrared action spectra of these ions at cluster sizes near the turnover size are largely independent of the specific identity of the trivalent metal ion, suggesting that any differences in the structures of the ions present in our experiment are subtle.