Anion Radicals and n Dianions

Chemically stable porphyrins can be reduced with sodium anthrace-nide [C/oss (35)]  

Diamagnetic n dianions have also been obtained by reduction in aprotic solvents and surprisingly produce an electronic spectrum which resembles the normal spectra of metalloporphyrins [Closs (35), Peychal-Heiling (147, 148)]. 

Light-driven electron transfers between Chla and hydroquinones [Cho (30), White (200)] as well as between Chla and lumiflavin [Tu (184), 185)] have also been described and interpreted as simple models for some primary steps in photosynthesis [Wang (193)]. Through the use of j8 carotene as a quencher the rate constant for semiquinone radical formation in such a system was found to be 8.8 X 105 1/mol sec at —30° [Cho (30j. A descriptive theory of the relationships between the energy levels in different chlorophylls and the electron-transfer processes between them and other organic electron carriers has also been developed [Nelson (134)]. 

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