Visible-Light-Responsive Reversible Photoacid Based on a Metastable Carbanion
A new photoacid that reversibly changes from a weak to a strong acid under visible light was designed and synthesized. Irradiation generated a metastable state with high CH acidity due to high stability of a trifluoromethyl-phenyl-tricyano-furan (CF3PhTCF) carbanion. This long-lived metastable state allows a large proton concentration to be reversibly produced with moderate light intensity. Reversible pH change of about one unit was demonstrated by using a 0.1 mM solution of the photoacid in 95 % ethanol. The quantum yield was calculated to be as high as 0.24. Kinetics of the reverse process can be fitted well to a second-order-rate equation with k=9.78×102 M−1 s−1. Response to visible light, high quantum yield, good reversibility, large photoinduced proton concentration under moderate light intensity, and good compatibility with organic media make this photoacid a promising material for macroscopic control of proton-transfer processes in organic systems.
Johns, V. K., Peng, P., Dejesus, J., Wang, Z., & Liao, Y. (2013). Visible-Light-Responsive Reversible Photoacid Based on a Metastable Carbanion. Chemistry - A European Journal Chem. Eur. J., 20(3), 689-692. doi:10.1002/chem.201304226