Size dependence of blackbody radiation induced hydrogen formation in Al+(H2O)n hydrated aluminum cations and their reactivity with hydrogen chloride
Size dependence of blackbody radiation induced hydrogen formation in Al+(H2O)n hydrated aluminum cations and their reactivity with hydrogen chloride
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DOI：
10.1021/jp983696f
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发表时间：
1999-02-11
影响因子：
2.9
通讯作者：
Bondybey, VE
中科院分区：
文献类型：
--
作者：
Beyer, M;Achatz, U;Bondybey, VE
用FT-ICR质谱法研究了几秒钟时间尺度上捕获的水合铝团簇离子。黑体辐射，除了引起集群的逐步损失的个别水分子的碎片，诱导在水合铝簇Al+（H2O）（n）的簇内反应产生水合氢氧化物和释放分子氢。从线性尺寸依赖的水损失过程的个别速率常数的局部偏差是由于由于稳定的氢键桥的形成而导致的某些尺寸的刚性增加。与以前研究的水合离子相比，表面与内部溶剂化进行了讨论。在n = 11-24的尺寸范围内优先发生的簇内反应归因于协同质子转移机制，其中需要至少两个水分子的链在两个第一溶剂化壳层水分子之间转移质子，导致形成Al（OH）（2）（+）（H2O）、水合氢氧化铝阳离子和分子氢。n ≥ 13的Al+（H2O）（n）和所有研究的Al（OH）（2）（+）（H2O）（m）物种都能与HCl反应并“溶解”HCl。簇中HCl分子的最大数目强烈地取决于可用于溶剂化的水分子的数目。团簇中HCl的存在消除了团簇内反应的上限，这导致在黑体辐射的驱动下形成分子氢。这进一步证明了质子转移机制的有效性。
Trapped hydrated aluminum cluster ions are studied by FT-ICR mass spectrometry on a time scale of several seconds. Blackbody radiation, besides causing the fragmentation of the cluster by stepwise loss of individual water molecules, induces in hydrated aluminum clusters Al+(H2O)(n) an intracluster reaction yielding hydrated hydroxide and releasing molecular hydrogen. Local deviations of the individual rate constants for the water loss process from a linear size dependence are due to increased rigidity of certain sizes due to the formation of stabilizing hydrogen-bonded bridges. In comparison with previously studied hydrated ions, surface versus internal solvation is discussed. The preferential occurrence of the intracluster reaction in the size region of n = 11-24 is attributed to a concerted proton-transfer mechanism, in which a chain of at least two water molecules is needed to transfer a proton between two first solvation shell water molecules, leading to formation of an Al(OH)(2)(+)(H2O), hydrated aluminum dihydroxide cation and molecular hydrogen. The Al+(H2O)(n) species with n greater than or equal to 13 and all investigated Al(OH)(2)(+)(H2O)(m) species are able to react with and "dissolve" HCl. The maximum number of HCl molecules in the cluster strongly depends on the number of water molecules available for solvation. The presence of HCl in the cluster removes the upper limit for the intracluster reaction, which leads to the formation of molecular hydrogen, driven by blackbody radiation. This is taken as further evidence for the validity of the proton-transfer mechanism.