RUI: Exploring Mechanistic Parameters Regulating Bond-Activation in the State-Specific Reactions of Gas Phase Transition Metal Ions with Halogenated Molecules

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In this project supported by the Chemical Structure, Dynamics and Mechanisms Program of the Division of Chemistry, Professor William Taylor of the University of Central Arkansas and his undergraduate research team will examine the activation of sigma bonds in halogenated molecules by metal ions. The reactions of interest will be carried out in the gas phase using a selected ion drift cell reactor which will generate transition metal ions in both ground and excited electronic states using a sputtering glow discharge source. These ions will then be mass selected via a quadrupole mass filter and introduced into a drift cell containing low pressures of helium and the neutral reactant molecule of interest. Subsequent analysis of reaction products will be carried out using a second quadrupole. This instrument will also be used to characterize the metal ion electronic state distributions via electronic state chromatography (ESC). ESC will also be used to determine the state-specificity of reaction products. Neutral reaction species will include various halogenated methanes (CH3X, CF3X, where X =Cl, Br and I), SF5Cl and SF5Br, and others. The experiments are designed to reveal the dependence of reaction outcome (e.g., halogen or halide abstraction, HX elimination) on various parameters, including the electronic state of the metal species as well as structural characteristics of the reactant neutral. Temperature dependent kinetic studies of selected reactions will be aimed at identifying likely transition states. These experimental efforts will be complemented by ensity functional calculations of reaction potential energy surfaces. Transition metal ions have the ability to break sigma bonds, and this property is most useful in converting hydrocarbons to other, more useful compounds. Understanding the mechanism of this process will allow design of new and better catalysts for use in chemical synthesis and the petroleum industry. In addition, the project will provide research opportunities to undergraduates in an area which they might not otherwise be exposed to. Undergraduates participating in this work benefit from a valuable research experience which serves them well in a variety of subsequent career choices including graduate/professional programs and science-related jobs.