title: Visible-light-responsive reversible photoacid based on a metastable carbanion.
abstract: 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 CH acidity due to high stability of a trifluoromethyl-phenyl-tricyano-furan (CF3 PhTCF) 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=9.78×10(2)  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.
authors: Department of Chemistry, Eastern Kentucky University, Richmond, KY 40475 (USA).
authors: Valentine K
authors: VK
authors: Johns
authors: Ping
authors: P
authors: Peng
authors: Joseph
authors: J
authors: DeJesus
authors: Zhuozhi
authors: Z
authors: Wang
authors: Yi
authors: Y
authors: Liao
keywords: UV/Vis spectroscopy; carbanions; photoacids; photochemistry