Two-photon absorption properties of conjugated supramolecular porphyrins with electron donor and acceptor

Two-photon absorption (2PA) cross-section values of supramolecular porphyrin tetramer consisting of two monoacetylene-linked bisporphyrins with and without ferrocene/C60 groups as electron donor/acceptor through the coordination of pyridyl to zinc were measured using a nanosecond open aperture Z-scan method. The maximum effective cross-section value was observed for the compound having asymmetric terminals of ferrocene and C60 as 2.0 × 105 GM. The values obtained for compounds having two C60's, two ferrocene's, no donor/acceptor, and stacked isomer were 1.7 × 105 GM, 1.5 × 105 GM, 1.1 × 105 GM, and 1.3 × 105 GM, respectively. These results indicate that the asymmetric donor–π–acceptor structure is the best for 2PA enhancement for this series of molecules. These values are extremely large compared to those of unit dimer 2D (190 GM at 780 nm) and compounds reported hitherto in literatures.