SET-promoted photoaddition reactions of N-α-trimethylsilylmethyl-N,N-dibenzylamines with fullerene C₆₀. Electronic factors that govern photoaddition efficiencies

Single electron transfer (SET) promoted photoaddition reactions of N-α-trimethylsilylmethyl-N,N-dibenzylamines to fullerene C₆₀ were investigated as part of an effort aimed at developing a general method to prepare various aryl ring containing aminomethylfullerenes and exploring factors that govern photoaddition efficiencies. The results show that the photoaddition reactions take place highly efficiently to form 1,2-adducts. The mechanism for this process involves generation of aminium radicals and C₆₀ anion radical intermediates by a pathway initiated by excited state SET. SET is followed by desilylation of the aminium radicals to produce α-amino radicals that couple with either C₆₀ or its radical anion to form precursors of the 1,2-adducts. The electronic nature of para-substituents on the aryl ring of N-α-trimethylsilylmethyl-N,N-dibenzylamines has a pronounced effect on the efficiency of the photoaddition reaction, with electron donating groups causing a greater than 2-fold enhancement compared to that brought about by electron withdrawing groups.