A series of polycyclic aromatic hydrocarbon-substituted metal-free porphyrins: Substituent effect on two-photon absorption property

The third-order nonlinear optical properties of a series of naphthyl, phenanthrenyl, and pyrenyl substituted porphyrins have been comparatively investigated by performing the femtosecond-pulsed Z-scan measurements. Due to the expanded it system, both pyrenly substituted porphyrin (1) and phenanthrenly substituted porphyrin (2) exhibit large two-photon absorption cross sections up to 4.26 x 10(4) GM for 1 and 1.36 x 10(4) GM for 2 at the wavelength of 800 nm. The pyrenly substituted porphyrin (1) has the most excellent two-photon absorption property because of the intramolecular energy transfer from the excited pyrene moiety to the porphyrin moiety in porphyrin 1. The results confirm that porphyrins conjugated with external pi electronic systems can lead to the significant enhancement in the two-photon absorption cross-section values. This research provides a useful guideline to the design of efficient two-photon absorbing materials. (C) 2017 Elsevier Ltd. All rights reserved.