1. Proton-Stabilized Photochemically Reversible E/Z Isomerization of Spiropyrans.
- Author
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Kortekaas, L., Chen, J., Jacquemin, D., and Browne, W. R.
- Subjects
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ISOMERIZATION , *SPIROPYRANS , *MEROCYANINES , *NUCLEAR magnetic resonance , *SPECTROMETRY - Abstract
Spiropyrans undergo Cspiro--O bond breaking to their ring-open protonated E-merocyanine form upon protonation and irradiation via an intermediate protonated Z-merocyanine isomer. We show that the extent of acid-induced ring opening is controlled by matching both the concentration and strength of the acid used and with strong acids full ring opening to the Z-merocyanine isomer occurs spontaneously allowing its characterization by 1H NMR spectroscopy as well as UV/vis spectroscopy, and reversible switching between Z/E-isomerization by irradiation with UV and visible light. Under sufficiently acidic conditions, both E- and Z-isomers are thermally stable. Judicious choice of acid such that its pKa lies between that of the E- and Z-merocyanine forms enables thermally stable switching between spiropyran and E-merocyanine forms and hence pH gating between thermally irreversible and reversible photochromic switching. [ABSTRACT FROM AUTHOR]
- Published
- 2018
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