フラーレンとポルフィリンからなる超分子系ナノカーボンの配列制御と光・電子物性

抄録

We have studied the supramolecular structures and photoelectronic properties of inclusion complexes of cyclic porphyrin dimers (M₂-CPD_Py, M=Ni, 2H) and fullerenes (C₆₀, C₇₀, PCBM ([6,6]-phenyl-C₆₁-butyric acid methyl ester) and Li⁺@C₆₀). The porphyrin dimers have self-assembling 4-pyridyl groups at the meso positions and include fullerenes in their cavities with high affinities (K_assoc≈10⁵ M^-1). In crystals, C₆₀⊂Ni₂-CPD_Py and PCBM⊂Ni₂-CPD_Py give self-assembled porphyrin nanotubes containing the linear arrays of fullerene molecules. These self-assemblies are induced mainly by the non-classical hydrogen bonds between pyridyl nitrogens and porphyin β C-H groups. On the other hand, in the crystals of C₆₀⊂H₄-CPD_Py and C₇₀⊂H₄-CPD_Py, the included fullerene molecules show zigzag chains through van der Waals contacts with each other. Due to these well-ordered arrays of C₆₀, both crystals of C₆₀⊂Ni₂-CPD_Py and C₆₀⊂H₄-CPD_Py have high charge mobilities (Σμ>0.1 cm² V^-1 s^-1). C₆₀⊂H₄-CPD_Py shows photoinduced electron transfer from the porphyrin moieties to C₆₀ and photovoltaic activity with IPCE_max=17% in photoelectrochemical cells. Moreover, the inclusion complexes of lithium-ion-encapsulated C₆₀(Li⁺@C₆₀) and M₂-CPD_Py exhibit photoinduced charge separation with very long lifetimes reaching submillisecond order.