Most common organic molecules do not absorb visible light (400-800 nm), that accounts for 44% of the incoming solar spectrum. In the last few decades, Ru and Ir polypyridyl complexes have been widely exploited as visible light photocatalysts. However, the expensive nature of metal photocatalyst and toxicity limits its application. On the other hand, organic dyes are known to be active visible light photocatalyst to catalyze the direct C−H bond arylation of heteroarenes with aryl diazonium salt, reduction of aryl halides and many other reactions. Herein, we have reported a metal free, non-toxic and cheap method for oxidation of alcohols and alkanes to their corresponding carbonyl compounds (image below). Organic dyes coupled with thiocyanate, a pseudohalide, has been used for the partial oxidation of alcohols as well as alkanes to carbonyl compounds. Pseudohalides are well known to do similar chemistry like halides. Thiocyanate radicals (SCN) are generated from readily available thiocyanate salts using organic dyes (Rose Bengal = RB) through single electron transfer (SET) in presence of visible light and oxygen as the terminal oxidant. Thiocyanate radicals abstract hydrogen like other halide radicals, so this aspect of chemistry was used for the oxidation of alcohols as well as alkanes to their corresponding aldehydes and other oxygenated products.

Pseudohalide assisted aerobic oxidation of alcohols and alkanes in presence of visible-light

254th National Meeting (2017)

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