Size-restricted proton transfer within toluene-methanol cluster ions.
Size-restricted proton transfer within toluene-methanol cluster ions.
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甲苯-甲醇簇离子内尺寸限制的质子转移。
DOI：
10.1021/jp8041186
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发表时间：
2008
期刊：
影响因子：
--
通讯作者：
Garvey,JamesF
中科院分区：
文献类型：
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作者：
Chiang,Chi-Tung;Shores,KevinS;Freindorf,Marek;Furlani,Thomas;DeLeon,RobertL;Garvey,JamesF
为了了解甲苯与甲醇之间的相互作用，采用串联四极杆质谱法和计算方法研究了{(C6H5CH3)(CH3OH)n=1−7}+簇离子的化学反应性。碰撞诱导解离（CID）实验表明，解离的簇内质子从甲苯阳离子转移到甲醇簇，形成质子化的甲醇簇，只发生在形式= 2−4。形式= 5−7，CID光谱显示，这些较大的团簇必须依次失去甲醇单体，直到它们达到n= 4，以引发甲苯阳离子的去质子化。亚稳态衰变数据表明，形式= 3和n= 4 (CH3OH)3H+是首选碎片离子。计算结果表明，甲醇亚团簇的总质子亲和力和团簇本身的结构在驱动质子转移反应中起重要作用。当n= 3时，亚簇中甲醇的协同作用为簇内质子转移反应的发生提供了最重要的贡献，使得簇内质子转移反应很少或没有能量屏障。Asn≥4时，甲醇亚团簇能够形成环状结构以稳定团簇结构，因此直接质子转移不是一个有利的过程。首选反应产物（CH3OH）3H+簇离子表明，这种限制尺寸的反应是由质子亲和性和增强的产物稳定性共同驱动的。
To understand the interaction between toluene and methanol, the chemical reactivity of {(C6H5CH3)(CH3OH)n=1−7}+cluster ions has been investigated via tandem quadrupole mass spectrometry and through calculations. Collision Induced Dissociation (CID) experiments show that the dissociated intracluster proton transfer reaction from the toluene cation to methanol clusters, forming protonated methanol clusters, only occurs forn= 2−4. Forn= 5−7, CID spectra reveal that these larger clusters have to sequentially lose methanol monomers until they reachn= 4 to initiate the deprotonation of the toluene cation. Metastable decay data indicate that forn= 3 andn= 4 (CH3OH)3H+is the preferred fragment ion. The calculational results reveal that both the gross proton affinity of the methanol subcluster and the structure of the cluster itself play an important role in driving this proton transfer reaction. Whenn= 3, the cooperative effect of the methanols in the subcluster provides the most important contribution to allow the intracluster proton transfer reaction to occur with little or no energy barrier. Asn≥ 4, the methanol subcluster is able to form ring structures to stabilize the cluster structures so that direct proton transfer is not a favored process. The preferred reaction product, the (CH3OH)3H+cluster ion, indicates that this size-restricted reaction is driven by both the proton affinity and the enhanced stability of the resulting product.