SYNTHESIS AND CHARACTERIZATION OF DOUBLY-STRAPPED PORPHYRINS

Synthesis of a ''doubly-strapped'' porphyrin is described, which has two -O(CH2)10O- straps on both sides of the porphyrin ring. This porphyrin did not form the zinc complex when treated with zinc acetate, even under forcing conditions. Such inertness toward zinc insertion can be attributed to the steric hindrance of the -O(CH2)10O- straps. Oligoporphyrins with one strapped ring were also synthesized. Reaction of these porphyrins with zinc acetate resulted in insertion of zinc into all non-strapped rings, while the strapped ring remained unchanged. These doubly-strapped porphyrins will be useful in constructing oligoporphyrins as photosynthetic model compounds, in which photochemical and electrochemical properties are controlled by selective metal insertion.