The structures and dynamic behavior of macrocyclic compounds consisting of three or four 9,10‐triptycyl units and 1,2‐phenylene and ethynylene frameworks were studied as multiple‐gear systems. These compounds were synthesized from 9,10‐diethynyltriptycene derivatives and a diiodobenzene by repeated Sonogashira coupling reactions. DFT calculations revealed that the benzene rings in the triptycene units meshed with each other in the inside region, which led to overall attractive interactions through π···π and CH···π contacts, regardless of the significant molecular deformations in the trimer. The symmetric 1H NMR signal pattern implied that the rotation of the gear moieties takes place rapidly, even at a low temperature. We analyzed the rotational mechanisms of the dynamic behavior by DFT calculations, for which the rotation was partly or fully correlated. The estimated rotational barriers were very low at 22.5 and 3.9 kJ mol–1 for the trimer and tetramer, respectively.

Three macrocyclic compounds consisting of four or six triptycene-9,10-diyl units and acetylene and phenylene linkers were synthesized as multiple-gear systems. These compounds were synthesized by macrocyclization of acyclic precursors via Eglinton coupling. DFT calculations showed that two or three triptycene units meshed with each other in the macrocyclic frameworks with CÀ H···π contacts. The 1 H NMR spectra of these compounds were symmetric at room temperature, and the signals became slightly broad at low temperature. These observations suggest that the gear moieties rotate rapidly on the NMR time scale.[a] Prof.