A Supramolecular Oscillator Composed of Carbon Nanocluster C120 and a Rhodium(III) Porphyrin Cyclic Dimer

A rhodium(III) porphyrin cyclic dimer (1) included carbon nanocluster C120 (2) to form a π-electronic supramolecular complex (1⊃2), in which 2 oscillated back and forth within its cavity. Spectroscopic titration of 1 with 2 and line shape analysis on variable-temperature 1H NMR spectral profiles of 1⊃2 and reference inclusion complexes in toluene-d 8, chlorobenzene-d 5, and dichlorobenzene-d 4 indicated that the association constant (K assoc) of 1⊃2 and oscillation activity of included 2 are both larger as the affinity of the solvent toward fullerenes is smaller. The ΔS ⧧ values for the oscillation were all positive, indicating that the oscillation of 2 involves desolvation of a protruding C60 moiety of included 2 from the host cavity.