Synthesis and properties of hybrid porphyrin tapes

Hybrid porphyrin tapes 3 and 4, consisting of a mixture of 3,5-di-tert-butylphenyl-substituted donor-type Zn ^II-porphyrins and pentafluorophenyl-substituted acceptor-type Zn ^II-porphyrins, were prepared by a synthetic route involving cross-condensation reaction of a Ni ^II-porphyrinyldipyrromethane and pentafluorophenyldipyrromethane with pentafluorobenzaldehyde followed by appropriate demetalation, remetalation, and oxidative ring-closure reaction. The Ni ^II-substituted porphyrin tapes 5 (Ni-Zn-Ni) and 6 (Ni-H ₂-Ni) were also prepared through similar routes. The hybrid porphyrin tapes 3 and 4 are more soluble and more stable than normal porphyrin tapes 1 and 2 consisting of only donor-type Zn ^II-porphyrins. The solid-state and crystal packing structures of 3, 4, and 5 were elucidated by single-crystal X-ray diffraction analysis. Singly meso-meso-linked hybrid porphyrin arrays 12 and 14 exhibit redox potentials that roughly correspond to each constituent porphyrin segments, while the redox potentials of the hybrid porphyrin tapes 3 and 4 are positively shifted as a whole. The two-photon absorption (TPA) values of 1-6 were measured by using a wavelength-scanning open aperture Z-scan method and found to be 1900, 21 000, 2200, 27 000, 24 000, and 26 000 GM, respectively. These results illustrate an important effect of elongation of π-electron conjugation for the enhancement of TPA values. The hybrid porphyrin tapes show slightly larger TPA values than the parent ones.