Supramolecular Structures and Photoelectronic Properties of π-Complexes Composed of Self-Assembling Cyclic Porphyrin Dimers and Fullerenes

Abstract

We have prepared nickel complexes and freebases of cyclic porphyrin dimers linked by butadiyne or phenothiazine groups. The porphyrin dimers have self-assembling pyridyl groups at the opposite meso positions and include fullerenes such as C₆₀, PCBM, C₇₀, and Li⁺@C₆₀ to give π-complexes. In particular, the phenothiazine-bridged cyclic porphyrin dimers exhibit notable high affinities toward C₆₀ (K _assoc > 10⁶ M⁻¹) and C₇₀ (K _assoc > 10⁷ M⁻¹). In the crystal structures, the π-complexes of C₆₀ and PCBM within the butadiyne-bridged nickel dimer and the phenothiazine-bridged freebase dimer afford self-assembled porphyrin nanotubes containing the linear arrays of the fullerenes. These self-assemblies are formed by the C-H · · · N hydrogen bonds and π-π interactions of the meso pyridyl groups. On the other hand, the π-complexes of C₆₀ and C₇₀ within the butadiyne-bridged freebase dimer gave the zigzag chains of the fullerenes through van der Waals contacts with each fullerene. These well-ordered C₆₀ arrays yield high electron mobilities (Σμ > 10⁻¹ cm²V⁻¹ s⁻¹). The π-complexes of C₆₀ and Li⁺@C₆₀ within the butadiyne-bridged dimers perform photoinduced electron transfer from the porphyrins to the fullerenes to give the CS states. The π-complexes of Li⁺@C₆₀ with the butadiyne-bridged dimers afford the CS states of remarkably long lifetimes reaching submillisecond order.