Strong two-photon absorption enhancement in a unique bis-porphyrin bearing a diketopyrrolopyrrole unit

A pi-extended bis-porphyrin bridged via a diketopyrrolopyrrole unit was prepared in 5 steps. This fully conjugated pi-system displays strongly distorted linear absorption, while its two-photon absorption cross-section reaches 2500-3000 GM at 940 nm. LC-like behaviour, easy orientation and low viscosity are, according to XRD, POM and DSC measurements, due to formation of plastic rather than a liquid crystal.