Synthesis and Photostability of Cyclooctatetraene-Substituted Free Base Porphyrins

A series of free base meso-tetraarylporphyrins functionalized with substituents containing one, two, and four cyclooctatetraene (COT) moieties have been obtained characterized by spectral photophysical studies. Three COT-free porphyrins served as reference compounds. COT is a triplet quencher, well-known to enhance the photostability several, but not all, fluorophores. In case porphyrins, substitution improves in zinc derivatives, for bases, effect opposite. We show that placing moiety further from porphyrin core enhances when group lies direct vicinity macrocycle. The quantum yields photobleaching inversely correlate oxidation potentials. An improvement both COT-containing can be achieved screening oxygen switching tolyl mesityl substituents. This leads decrease yield, even though lifetimes are longer. results confirm involvement photodegradation porphyrins.