Structure–Property Relationship of Supramolecular Rotators of Coronene in Charge-Transfer Solids

Single
crystals of charge-transfer (CT) complexes composed of the
polyaromatic hydrocarbon, coronene, as an electron donor (D) and 7,7,8,8-tetracyanoquinodimethane
(TCNQ) analogues as electron acceptor (A) were obtained. Elucidation
of crystal structures of CT complexes enables a systematic investigation
of dynamic properties of coronene molecules lying in different types
of crystalline environments. Solid-state 2H NMR spectra
of CT complexes formed with deuterated coronene confirmed the in-plane
6-fold flipping motion of the coronene molecules. The dihedral angle
between adjacent coronene and TCNQ analogue within the DA-type alternating
π-column is closely correlated with the dynamic properties,
such as rotational rate and activation energy. Side-by-side intermolecular
hydrogen-bonding also seems to have an effect in ways that lead to
the suppressed rotation. These findings would provide an initial step
toward the selection, design, and engineering of counter components
of supramolecular rotators in the CT solids.