Efficient halogen photoelimination from dibromo, dichloro and difluoro tellurophenes

Abstract

We present the reactivity and photochemistry of 2,5-diphenyltellurophene. A change in oxidation state from Te(II) to Te(IV) occurs by oxidative addition of bromine, chlorine, and fluorine from appropriate halogen sources. Photoreductive halogen elimination is demonstrated using optical absorption spectroscopy and NMR spectroscopy. The photodebromination reaction occurs with 16.9% quantum yield, the highest value for any Te compound. Photoreductive elimination of chlorine and fluorine occurs with quantum yields of 1.6% and 2.3%, respectively, albeit with less efficient halogen trapping when an organic trap is used. Improved fluorine trapping was achieved using water, allowing for much cleaner photodefluorination. This is the first example of photodefluorination from a tellurium compound.