Large two photon absorption cross section of asymmetric Zn(II) porphyrin complexes substituted in the meso or β pyrrolic position by -CC-C6H4X moieties (X = NMe2, NO2)

A large two photon absorption (TPA) cross section of about 4000 GM is measured by Z-scan technique for a push-pull A-pi-D Zn(II) porphyrin complex disubstituted in the meso position with strong donor and acceptor moieties. This result is compared to the lower TPA cross section of Zn( II) porphyrinates mono-substituted in the meso or beta pyrrolic position with the same donor or acceptor substituents. The origin of such trend is discussed in terms of charge transfer processes, pi delocalisation and resonance pathways. (c) 2008 Elsevier B. V. All rights reserved.