Complex formation between a tetramesityl sulfonated resorcarene and alkylammonium ions: a mass spectrometric study of noncovalent interactions

Noncovalent complex formation between a tetramesityl sulfonated tetramethyl resorcarene and primary, secondary, and tertiary alkylammonium ions was investigated by electrospray ionization (ESI) Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry. Competition measurements, collision-induced dissociation, and gas-phase hydrogen/deuterium (H/D)-exchange reactions were employed to elucidate the interactions involved in complexation, the stability of the complexes, and the position of the guest with relation to the resorcarene. The complex formation ability of tetramesityl sulfonated resorcarene and the stability of the compexes were compared with the corresponding properties of tetratosylium tetraethyl resorcarene, which has been studied previously. Complex formation and the properties of the complexes were most strongly determined by the steric properties of the guests and their ability to form hydrogen bonds. Comparison of the two host molecules revealed the impact of steric hindrance in tetramesityl sulfonated tetramethyl resorcarene.