Ultrafast motion of molecular rotors in metal-organic frameworks: a muon-spin relaxation study

In recent years, amphidynamic crystals have gained more and more attention as a state of matter somehow intermediate between solids and liquids. In fact, although these systems are well-behaved in terms of long-range crystallographic order, specific moieties within the crystal can realize very fast rotary motions along specific crystallographic axes with remarkably low activation energies, offering novel exciting prospects of applications. The goal of this proposal is to use muons to investigate the dynamical properties of an amphidynamic crystal realised with rod-like molecular rotors embedded into an extended metal-organic framework. For the appealing system being specifically considered, the characteristic activation energies for rotations were reported very recently to be even lower than the ambient thermal energy, making the motion particularly fast even well below room temperature.