Triphenyl imidazolyl radical

A 0.5% benzene solution of the above product turned purple on exposure to sunlight, the coior fading in 45 seconds. From optical density measurements of the 558 mil absorption band obtained as described in Example I, the color fading rate value was 17, indicating a fading 70 rate of about 35 times that of the art 2,4,5-triphenyl-imidazolyl radical with a value of 0.46 taken as a control. 

The flash photolysis of hexaarylbiimidazole produces imidazolyl radicals " which have been shown to be more nearly planar than the parent dimers ort/io-substituents in the aryl rings decrease the radical stability. The radicals oxidize electron-rich substrates by rapid electron abstraction from tertiary amines, iodide, and metal ions, and by hydrogen abstraction from phenols, mercaptans, secondary amines, and active methylene com-pounds." " Studies have been made of the photooxidation of /euco-triphenyl-methane dyes by these radicals." " ... 

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