Polymer‐bound porphyrins and their precursors, 10. Syntheses and photoredox properties of water‐soluble polymers with covalently bonded zinc tetraphenylporphyrin

Positively or negatively charged as well as uncharged water‐soluble polymers 2a – d, 6a – c, 7a – e and positively charged crosslinked polymers 3a, b containing covalently bonded moieties of the substituted zinc tetraphenylporphyrin 1a were prepared. In addition, positively charged polymers 4a – c with covalently bonded viologen, and 5 with covalently bonded 1a and viologen at one and the same polymer chain were obtained. The triplet lifetimes in water of different 1a‐ bonded linear polymers 2a – d, 6a – c, and 7a – e are not influenced by the kind of polymer environment. The photoredox activites in water of the polymers containing moieties of 1a in the presence of methylviologen and 2‐mercaptoethanol under irradiation with visible light are higher as compared with low‐molecular‐weight, positively or negatively charged porphyrins 1b, c. The influence of the amount of polymer‐bonded porphyrin and the molecular weight of a polymer on the photoredox activity is exemplarily described. Polymers 4a – c with viologen moieties as acceptor are more efficient than the low‐moleular‐weight methylviologen. The highest photoredox activities were observed with polymer 5 containing moieties of 1a and viologen. In the presence of the enzyme hydrogenase formation of hydrogen occurs.