Abstract by Jamir Shrestha
Tina H M Farzan
David V. Dearden
Chemistry and Biochemistry
Determining Topologies of Alkylammonium Complexes of Cucurbiturils Using Multi-CRAFTI Techniques in an FTICR Mass Spectrometer
Cucurbit[n]urils (CB[n]) are hollow, pumpkin-shaped molecules with two identical cation binding sites at the two carbonyl oxygen-lined portals and a non-polar interior that can bind neutrals. Singly charged 1:1 and doubly charged 1:2 CB complexes with alkylmonoammonium ions were detected in the gas phase in an FTICR instrument. In complexes with n-alkylammonium ions, the alkyl chains may be outside, inside or partially inside the cage. These conformers have identical masses and similar fragmentation behavior, but differ in collision cross-section (CCS). We applied a new technique (“CRAFTI”) to compare the CCS and distinguish between internal and external conformers. We used Spartan’18 with the MMFF94 force field and the IMoS projection approximation to compute structures and CCS. FTICR linewidths were measured as a function of collision gas pressure and kinetic energy, which enabled calculation of relative CCS as a function of collision energy.