The project involves mass spectrometry studies of the thermochemical properties of the reactivity of open-shell molecules and ions. The proposal describes studies designed to investigate the mechanisms through which electrons can interact in open-shell systems. The goal of the work is to provide insight into how to control the spin of open-shell system by strategically choosing structural motifs that exploit the appropriate mechanistic aspects. The three methods of controlling spin are: 1) Topological approaches : the focus of this area is on disjoint diradicals and using connectivity to create them in either triplet or singlet states. The role of topology will be investigated by contrasting the properties, such as electron affinities, of structurally related but topologically distinct bis-allylic diradicals. 2) Heteroatom substitution : replacing a carbon in well-studied hydrocarbon diradicals with nitrogen or oxidized nitrogen can change the ground and excited state energy orderings. This effect will be investigated by examining the thermochemical properties of pyridine- and pyridine-n-oxide based diradicals, determined by using energy-resolved collision-induced dissociation studies. 3) Substitution : the electronic state ordering of aromatic nitrenes is altered by using substituents either on the aromatic ring or next to the nitrene center. Negative ion photoelectron spectroscopy of substituted phenylnitrene radical anions will be used to investigate the electron affinities and the energies of the excited states in the neutral phenyl nitrenes. Gas-phase studies of reactivity and structure can impact all areas of chemistry as well as other disciplines such as material science and engineering. Mechanistic studies provide insight that can be used to develop new reactivity methodologies. Whereas structural studies of open-shell species such as diradicals and triradicals provide insight into bonding and reactivity, they also provide a foundation for engineering and material science approaches to magnetic materials. The work described in this proposal is also an important component of the education of a diverse and talented group of graduate students at Purdue University. This support also allows the PI to utilize his experience with the NSF Graduate Research Fellowship Program to encourage and activities of the undergraduate students in the local ACS Student Affiliates and Alpha Chi Sigma chapters, particularly in regards to developing creative ways for the students to serve and impact the community.
