Addressing the Barrelene Core of Triptycene with Muon Spin Resonance Spectroscopy

Understanding the degrees of freedom of movement of molecules in the condensed phase is critical for informing the design of new molecular materials. Here we have applied muon spin resonance spectroscopy (μSR) to study the three-dimensional (3D) polycyclic aromatic hydrocarbon triptycene in the solid phase. This was inspired by the rotational dynamics observed in previous μSR studies of the archetypical 3D molecular electronic materials, the fullerenes. We identified that there is only limited motion of triptycene in its crystals. We also make the intriguing observation that muonium adds to the barrelene core of the molecules which may provide a powerful new method to examine through-space interactions between aromatic rings.