Reports: ND650994-ND6: Ion-Molecule Chemistry of Bare Metal Anions

Paul Michael Mayer, PhD, University of Ottawa

The chemical concept of metals producing positive ions (cations) and non-metals negative ions (anions), is a fundamental precept taught as early as high school. However, under certain conditions metal anions can be created and as such their electron affinities are well characterized and calculated both experimentally and theoretically. We have a new method for generating metal anions and are exploring their reactions with small neutral molecules. When the metal ion is allowed to react with a neutral molecule in the collision hexapole of the triple quadrupole mass spectrometer, we observe both electron transfer and atom abstraction reactions, depending on the species concerned. When electron transfer dominates, we can theoretically model the reaction breakdown curves to extract the exo- or endothermicity of the process, which directly gives the electron affinity (EA) of the neutral reagent since the EA of the metal is known. For some metals such as Ag- and Fe-, reaction with O2 in the cell results in O atom extraction to form AgO- and FeO-. We are using experiment and theory (ab initio MO calculations) to probe the mechanisms of ion-molecule reactions of metal anions. The reactivity of metal anions is pretty much an open book, waiting to be discovered. This ACS PRF grant has funded two graduate students and six undergraduate students over the past year. Four students' research focused on the reactions of atomic metal anions with small substituted methanes (CH3Cl, CH3NO2 and CH3CN), alcohols, alkanes, alkenes and alkynes, as well as fluorination aromatic systems. Each of these students is suing this opportunity to expand their experience in research and development. Two will obtain MSc degrees. Of the undergraduates involved in this part of the work, one used his experience to successfully enter medical school while another took advantage of his training to pursue further graduate work at Carleton University. One undergraduate pursued the assessment of computational levels of theory for reliable theoretical modeling of these systems, and he started his MSc at Dalhousie University this fall. The sixth student explored alternative routes to the formation of the metal anions, and she (Julie Roy) started an MSc degree in Inorganic Chemistry this fall. This grant also helped us be successful in an NSERC equipment grant application to obtain a mass spectrometer exclusively to examine the ion chemistry of atomic metal anions. It has opened up a new collaboration with the research group of Oliver Hampe at the Karlsruher Institute fur Technology exploring the spectroscopy and ion mobility of the complexes responsible for forming atomic metal anions in the gas phase. Thus this ACS PRF grant has not only allowed me to open up a new area of research in ion chemistry, but it has been multiplied by aiding successful infrastructure grants and creating new collaborations.