Reactivity of self-assembled supramolecular complexes in the gas phase: A supramolecular neighbor group effect

Infrared multi-photon dissociation (IRMPD) spectra of mass-selected, self-assembled supramolecular squares and their gas-phase fragments have been recorded in a Fourier-transform ion-cyclotron resonance (FT-ICR) mass spectrometer. The squares have been transferred into the gas phase by electrospray ionization (ESI) under very soft ionization conditions resulting in a series of signals for intact squares in different charge states by stripping off two or more counter ions. The fragmentation patterns of the squares strongly depend on the parent ion's charge state. For species with a lower number of charges, expulsions of edge ligands prevail, whereas charge separation pathways dominate the dissociation pathways of more highly charged species.