Reverse saturable absorption in the near-infrared by fused porphyrin dimers

A new class of macrocyclic dyes, specifically triply linked porphyrin dimers was presented with the goal of extending the region of RSA to longer wavelength. In prophyrins and phthalo-cyanines the useful RSA region lies between the Q and Soret absorption bands, where the ground state absorption is low. The new approach enabled to identify fused porphyrin dimers with significant triplet yields and thereby demonstrate RSA on the nanosecond timescale in the near-infrared region. It was found that by use of meso-bromo and meso-iodo substituents triplet yield could be achieved which allows to measure triplet state lifetimes and excited state absorption spectra