A Complete Gear System in N‑Benzoyl-Carbazole Derivatives

2′,6′-Disubstituted N-benzoylated carbazole derivatives were found to exhibit atropisomerism. The bulky substituents restricted rotation about the N–C7′ and C7′–C1′ bonds to separate four atropisomers, in which rotation about the C7′–C1′ bond was in perfect concert with rotation about the N–C7′ bond. Complete geared rotation without slippage at 37 °C for 7 days was observed for the first time. Conformational analysis clarified the preference for the gear system over other internal conversion pathways.