Photooxygenation and gas-phase reactivity of multiply threaded pseudorotaxanes

The solution‐phase photooxygenation of multiply threaded crown/ammonium pseudorotaxanes containing anthracene spacers is monitored by electrospray ionization Fourier‐transform ion‐cyclotron‐resonance (ESI‐FTICR) mass spectrometry. The oxygenated pseudorotaxanes are mass‐selected and fragmented by infrared multiphoton dissociation (IRMPD) and/or collision‐induced dissociation (CID) experiments and and their behavior compared to that of the non‐oxygenated precursors. [4+2]Cycloreversion reactions lead to the loss of O2, when no other reaction channel with competitive energy demand is available. Thus, the release of molecular oxygen can serve as a reference reaction for the energy demand of other fragmentation reactions such as the dissociation of the crown/ammonium binding motifs. The photooxygenation induces curvature into the initially planar anthracene and thus significantly changes the geometry of the divalent, anthracene‐spacered wheel. This is reflected in ion‐mobility data. Coulomb repulsion in multiply charged pseudorotaxanes assists the oxygen loss as the re‐planarization of the anthracene increases the distance between the two charges. Copyright © 2016 John Wiley & Sons, Ltd.