Ketocoumarin dyes as electron mediators for visible light induced carboxylate photorelease.

Photoinduced mediated electron transfer to N-alkylpicolinium(NAP)-based esters has previously been shown to induce release of carboxylate anions. In this mechanism, electrons are shuttled between a good electron donor through a sensitizer/mediator to the NAP group which subsequently induces C-O bond cleavage. Previous studies have used UV-absorbing mediators to initiate substrate release with high photorelease efficiencies, but require long irradiation periods for quantitative deprotection. The current study improves upon previous systems by using lower energy visible light absorbing mediators that induce substrate release over shorter irradiation periods (i.e. higher overall photolytic efficacies).