Anion Radical of Bacteriochlorophyll
Fajer, J., Borg, D.C., Forman, A., David Dolphin, and Felton, R.H.
J. Am. Chem. Soc.
The anion radical (BCh.- ) of bacteriochlorophyll (BChl) was prepared by controlled potential electrolysis in DMF or butyronitrile. Its optical absorption spectrum showed bleaching of the intense ir band, and appearance of absorption in the region of 900-1100 nm. The EPR spectrum displayed a 12-line, partially resolved HFS (hyperfine splitting) spectrum which narrowed by a factor of 1.5 upon deuteration. The anion radical of the model compd., 2,3,12,13-tetrahydro-5,10,15, 20-tetraphenylporphyrin Zn(II) had a similar absorption spectrum and a well-resolved EPR spectrum which permits the following assignments: aH7=1.80G, aH2 = 0.70, a N21 = 2.88, with aphenyl approximately 0.1. Comparison of Bchl.- properties with those assigned to the primary acceptor in bacterial photosynthesis led to the conclusion that BChl.- is not the primary acceptor.