Allosteric regulation of rotational, optical and catalytic properties within multicomponent machinery

Abstract

The reversible transformation of multicomponent nanorotors (ROT-1, k₂₉₈ = 44 kHz or ROT-2, k₂₉₈ = 61 kHz) to the “dimeric” supramolecular structures (DS-1 or DS-2, k₂₉₈ = 0.60 kHz) was triggered by a stoichiometric chemical stimulus. Simple coordination changes at the central phenanthroline of the molecular device by altering metal ions (Cu⁺ → Zn²⁺) or stoichiometry (Cu⁺, 1 equiv. → 0.5 equiv.) affected the terminal zinc(II) porphyrin units, the active sites within the machinery, changing rotational, catalytic and optical properties. In presence of added pyrrolidine, the nanorotor ROT-1 was inactive for catalysis whereas formation of the dimeric supramolecular structures DS-1 initiated a Michael addition reaction by releasing the organocatalyst from the porphyrin sites. This catalytic machinery (ROT-1 ⇄ DS-1) proved to reproducibly work over two full cycles using allosteric OFF/ON control of catalysis.