Photo-Activated Emission and Chirality Transfer Based on Host-Guest Chemistry of a Motorized All-Benzene Nanohoop

In this study, a series of motorized carbon nanohoops M[8]CPP, M[9]CPP and M[11]CPP are designed. Transient absorption (TA) spectra reveal these cyclic motors exhibit unprecedented acceleration of rotary speed upon incorporation into an all-benzene macrocyclic stator, which is attributed to ring strain induced decrease of the steric hindrance at the fjord region. Especially, M[8]CPP realizes 10⁷-fold increase of the rotation speed compared with the noncyclic motor. Such high rotation speed leads to the fluorescence quenching of the motorized carbon nanohoops. Interestingly, M[11]CPP possesses a rigid macrocyclic cavity, which can bind with C₆₀ and C₇₀ in 1:1 stoichiometric ratio. The formation of host-guest complexes decelerates the photo-isomerization processes of M[11]CPP and achieves photo-activated fluorescence emission of the host-guest systems. Furthermore, taking advantage of the intrinsic chirality of M[11]CPP, as well as the CH-π interactions between M[11]CPP and perylene, the chirality is transferred onto perylene, and circularly polarized luminescence is realized. This work not only provides a novel strategy for tuning the optical properties of cycloparaphenylenes through host-guest interactions but also demonstrates the potential of integrating molecular motors into macrocyclic systems to achieve dynamic control over molecular behavior.