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-CPD(Py) (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-CPD(Py) includes a C60 molecule in its cavity in solution. In the crystal structure of the inclusion complex (C60⊂H4-CPD(Py)), 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-CPD(Py) in the solid state with photoexcitation at 420 nm shows the formation of a completely charge-separated state {H4-CPD(Py)·+ + C60·−}, which decays with a lifetime of 470 ps to the ground state. The charge-carrier mobility of the single crystal of C60⊂H4-CPD(Py) was determined by flash photolysis time-resolved microwave conductivity (FP-TRMC) measurements. C60⊂H4-CPD(Py) 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-CPD(Py) 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%.
Nobukuni
Hirofumi
H
Institute for Materials Chemistry and Engineering, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan.
Shimazaki
Yuichi
Y
Uno
Hidemitsu
H
Naruta
Yoshinori
Y
Ohkubo
Kei
K
Kojima
Takahiko
T
Fukuzumi
Shunichi
S
Seki
Shu
S
Sakai
Hayato
H
Hasobe
Taku
T
Tani
Fumito
F
D018360:Crystallography, X-Ray; D019281:Dimerization; D004579:Electron Transport; D037741:Fullerenes / Q000737:chemistry*; D006860:Hydrogen Bonding; D008968:Molecular Conformation; D043942:Nanotubes / Q000737:chemistry; D010782:Photolysis; D011166:Porphyrins / Q000737:chemistry*; D012993:Solar Energy
D037741:Fullerenes; D011166:Porphyrins; C069837:fullerene C60