Ion-Molecule Chemistry within Boron Tribromide Clusters: Experiment and Theory

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• 作者：David A. Hales ; Kathryn E. Kautzman ; Nathan G. Williams ; Pamela A. Haile ; Michael P. Barker
• 刊名：Journal of Physical Chemistry A
• 出版年：2007
• 出版时间：March 29, 2007
• 年：2007
• 卷：111
• 期：12
• 页码：2266 - 2275
• 全文大小：377K
• 年卷期：v.111,no.12(March 29, 2007)
• ISSN：1520-5215

文摘

Molecular clusters of BBr₃ were subjected to electron ionization and mass analysis in a reflectron time-of-flight mass spectrometer. Five series of cluster ions were observed, with formulas corresponding to each ofthe possible fragment ions of BBr₃ being solvated by neutral BBr₃ molecules. Geometry optimizations on theobserved cluster ions using density functional theory (B3LYP/6-31G*) predict that fragment ions smallerthan BBr₃⁺ undergo reactions with neutral BBr₃ molecules to form covalently bound adduct species thatfunction as core ions within the clusters. Once all boron atoms are saturated, the reactions cease, and largercluster ions consist of BBr₃ molecules loosely bound to the core ions. Divalent bromine atoms are present inat least three of the cluster ions, and most of the intermolecular contact within the clusters is between Bratoms. Enthalpies of formation, addition reactions, and BBr₃ elimination from the cluster ions were derivedfrom B3LYP and MP2 calculations at the B3LYP/6-31G* geometries using both the 6-31G* and the6-311++G(2df,2p) basis sets. The results are compared to limiting expectations based on known bulkthermochemistry.