Engineering of\nRotational Dynamics via Polymorph Manipulation

We used dielectric spectroscopy to uncover the rotational\ndynamics\nof the fluorophenyl rotor in different polymorphs of two amphidynamic\ncrystals with identical sizable cores. The rotor solid-state dynamics\nwere investigated in various crystalline environments. We did not\nchange the chemical structure of the crystal itself, but while maintaining\nthe same atomic composition, we changed the arrangement of atoms in\nspace by taking advantage of crystal polymorphism, providing an alternative\napproach to one based on searching for new, chemically different entities\nwith desirable functionality. We demonstrated that via polymorph variation,\nwe can efficiently improve rotor solid-state performance and reduce\nthe rotational barrier height by 30%. Our findings advance the understanding\nof polymorph engineering as a prospective trend in amphidynamic crystal\ntechnology, which uses the phenomenon of crystal polymorphism to design\ncrystals displaying applicable internal rotational dynamics.