Supramolecular Structures and Photoelectronic Properties of the Inclusion Complex of a Cyclic Free-Base Porphyrin Dimer and C60

A cyclic free‐base porphyrin dimer H4‐CPDPy (CPD=cyclic porphyrin dimer) linked by butadiyne moieties bearing 4‐pyridyl groups self‐assembles to form a novel porphyrin nanotube in the crystalline state. The cyclic molecules link together through nonclassical CH⋅⋅⋅N hydrogen bonds and π–π interactions of the pyridyl groups along the crystallographic a axis. H4‐CPDPy includes a C60 molecule in its cavity in solution. In the crystal structure of the inclusion complex (C60⊂H4‐CPDPy), the dimer “bites” a C60 molecule by tilting the porphyrin rings with respect to each other, and there are strong π–π interactions between the porphyrin rings and C60. The included C60 molecules form a zigzag chain along the crystallographic b axis through van der Waals contacts with each other. Femtosecond laser flash photolysis of C60⊂H4‐CPDPy in the solid state with photoexcitation at 420 nm shows the formation of a completely charge‐separated state {H4‐CPDPy.++C60.−}, which decays with a lifetime of 470 ps to the ground state. The charge‐carrier mobility of the single crystal of C60⊂H4‐CPDPy was determined by flash photolysis time‐resolved microwave conductivity (FP‐TRMC) measurements. C60⊂H4‐CPDPy has an anisotropic charge mobility (Σμ=0.16 and 0.13 cm2 V−1 s−1) along the zigzag chain of C60 (which runs at 45° and parallel to the crystallographic b axis). To construct a photoelectrochemical cell, C60⊂H4‐CPDPy was deposited onto nanostructured SnO2 films on a transparent electrode. The solar cell exhibited photovoltaic activity with an incident photon to current conversion efficiency of 17 %. A zigzag array of C60 is formed in the crystal structure of its inclusion complex with a cyclic free‐base porphyrin dimer (see figure). The complex shows photoinduced electron transfer, anisotropic charge mobility, and photovoltaic activity.