1. Zheng Shi, Ping Peng, Daniel Strohecker, and Yi Liao*
J. Am. Chem. Soc., 2011, 133,
Long-Lived Photoacid Based upon a Photochromic Reaction
Zheng Shi, Ping Peng, Daniel Strohecker, and Yi Liao*
Department of Chemistry, University of Central Florida, Orlando, Florida 32816, United States

2. (Photoinduced) Proton Transfer
(Photosynthetic Process)
O. A. Sytina et al., Nature, 2008, 456, 1001.

3. Photoacid Generators (PAGs)
Photocleavage +
Hydrogen abstraction
Proton-transfer +
Acid generation
Irreversible process
*pH jump by photoexciation
(grand state)
(excited state) hn
pKa = 9.2
pKa = 2.0
Reversible process
Short lifetime of excited state

4. Photocontrol of Molecular and Supramolecular Events
*Control of complex formation
*H2 generation
J. L. Dempsey et al., JACS, 2010, 132,
*Locking of photoreactivity
M. Ohsumi et al., Chem. Commun., 2005, 3921.
S. Silvi et al., JACS, 2007, 129,

5. Photochromic Reaction of Spirobenzopyran
Vis. UV
MEH SP
(in polar solvent)
Stable form; MEH
(in non-polar solvent)
Stable form; SP
5.88 × 10-4 M (water)

6. Photoswitching of pH Value
5.88 × 10-4 M (water)

7. Lifetime of the Proton Dissociation-state
First order kinetics
k = s-1
t1/2 = 0.693/k
= 76 s
Long-lived proton-dissociation state

8. Substituent Dependence
(MEH)
pH = 4.9
less reactivity
low solubility
(SP)
pH = 3.9
DpH ~ 1.0

9. Photoinduced Catalyzing Property
(3.1 mM)
(12.5 mM)
(419 nm nm)
(Yield of Ethyl acetate)
1: 33 % (1h), 50 % (2h), 66 % (3h), 0 % (dark)
2: 0 % (3h)

10. Photoinduced the Volume Change of Hydrogel
(Before)
(After)
Vis.
A copolymer of poly(acrylic acid) and polyacrylamide
“Shrink”
(~ 1/8 volume)

11. Conclusions Ex. 1) (Before) (After) Vis. Ex. 2) pH ~ 5.5 pH ~ 3.5
“Shrink”
(~ 1/8 volume)