Spectroscopic properties of meso-thienylporphyrins with different porphyrin cores

The absorption and fluorescence properties of a series of meso-thienylporphyrins with different porphyrin cores (N4, N3O, N3S and N2S2 cores) were studied and compared with the corresponding meso-tetraarylporphyrins. The replacement of six-membered phenyl groups with five-membered thienyl groups at meso-positions resulted in red shifts and broadening of absorption and emission bands, low quantum yields and decreased S1 state lifetimes and the maximum effects were observed for meso-tetrathienylporphyrin with N2S2 porphyrin core. Similar observations were noted for the dications of meso-thienylporphyrins compared to the dications of the corresponding meso-tetraarylporphyrins. These results suggest that the replacement of six-membered aryl group with five-membered thienyl groups at meso-positions, the electronic properties of the porphyrin were altered significantly.