New conjugated meso-tetrathienylporphyrin-cored derivatives as two-photon photosensitizers for singlet oxygen generation

A series of conjugated mesa-porphyrin dendrimers containing conjugated fluorenyl dendrons, incorporating overall either four (3) or eight (4) fluorenyl units have been synthesized and characterized. These new molecular architectures are based on a central meso-tetra(thien-2-yl)porphyrin core (IThP). Their linear optical properties, absorption and photoluminescence, as well as selected nonlinear optical properties, were investigated and compared to those of the unsubstituted meso-(thien-2-yl)porphyrin core (5) and also to those of previously reported analogues featuring 1,4-phenylene groups (1 and 2) in place of 2,5-thienylene moieties. The positive role of these thienylene linkers over phenylene linkers on the two-photon absorption (2PA) cross-sections is clearly evidenced.