Synthesis and Two-Photon Spectrum of a Bis(Porphyrin)-Substituted Squaraine

A chromophore in which zinc porphyrin donors are linked through their meso positions by ethynyl bridges to a bis(indolinylidenemethyl) squaraine core has been synthesized using Sonogashira coupling. The chromophore exhibits a two-photon absorption spectrum characterized by a peak cross section of 11 000 GM and, more unusually, also exhibits a large cross section of >780 GM over a photon-wavelength window 750 nm in width.