Radical‐Pairing Interactions in a Molecular Switch Evidenced by Ion Mobility Spectrometry and Infrared Ion Spectroscopy

Abstract

The digital revolution sets am ilestone in the progressive miniaturization of working devices and in the underlying advent of molecular machines.F oldamers involving mechanically entangled components with modular secondary structures are among the most promising designs for molecular switch-based applications.Characterizing the nature and dynamics of their intramolecular network following the application of astimulus is the key to their performance.Here, we use non-dissociative electron transfer as ar eductive stimulus in the gas phase and probe the consecutive co-conformational transitions of ad onor-acceptor oligorotaxane foldamer using electrospraym ass spectrometry interfaced with ion mobility and infrared ion spectroscopy. Ac omparison of collision cross section distributions for analogous closed-shell and radical molecular ions sheds light on their respective formation energetics,while variations in their respective infrared absorption bands evidence changes in intramolecular organization as the foldamer becomes more compact. These differences are compatible with the advent of radical-pairing interactions.

Structural studies of supramolecular complexes and assemblies by ion mobility mass spectrometry

“…The electron transfer enables an analysis of (un)folding processes upon charge reduction, taking advantage of the non‐dissociative character of the electron transfer (ETnoD—Electron Transfer with no Dissociation). The combination of ETnoD and IM‐MS has emerged as a useful approach to unravel the (un)folding mechanisms of mechanically interlocked molecule—oligorotaxane (Hanozin et al, 2017, 2021). Its co‐conformations and the ability to perform contraction and extension depending on the charge state and the activation stimuli as key features determining its future application in artificial molecular muscle design were explored by IM‐MS and related techniques, including ETnoD (Figure 28).…”