The synthesis and photochemical characterization of meso-tetra-thienyl porphyrins

A series of meso -thienyl porphyrins were synthesized through Lindsey's procedure and characterized. Compared with H 2 TPP (tetraphenylporphyrin), the absorption and fluorescence spectra of thienyl porphyrins have red shift obviously which show that thienyl substituents at meso -position change the electronic structure of tetrapyrrole ring. With protonation using CF 3 COOH, the absorption bands of thienyl porphyrins are further red shifted. The absorption bands of meso -thienyl porphyrins change correspondingly with the variation of solvents’ properties, however the maxima emission wavelengths corresponding to Q * have little relation with solvents. And the fluorescence lifetime become so less even to 1.1 ns. The half-wave redox potential shows cathodic shift relative to H 2 TPP. These changes above are all ascribed to the introduction of thienyl group at meso -position and the possibility of more planarity of meso -thienyl porphyrins for the small size of thienyl group which is helpful to the extending π-delocalization of thienyl groups to the tetrapyrrole ring.