Dynamically switchable porphyrin-based molecular tweezer for on-off fullerene recognition

Herein, a novel molecular tweezer based on 2,2'-bipyridine-bridged porphyrin subunits was constructed for efficient fullerenes recognition. The syn conformation of the molecule, which was obtained by Zn（Ⅱ）coordination, gives rise to a proper cavity to interact with fullerene guests to form a stable 1:1 complex in toluene solution. It exhibits distinct binding selectivity towards C60 over C70. Moreover, the fullerene recognition capacity can be adequately suppressed by importing H2PO4- to competitively capture Zn（Ⅱ）along with syn-anti conformational conversion. Subsequently, the molecular tweezer regenerated to bind the fullerene by introducing the Ca2+into the system. Significantly, the association-disassociation process can be switched reversibly and repeatedly.