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Proton-Stabilized Photochemically Reversible E/ Z Isomerization of Spiropyrans.

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 p Ka 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.

SUBMITTER: Kortekaas L

PROVIDER: S-EPMC6150689 | biostudies-literature | 2018 Jun

REPOSITORIES: biostudies-literature

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Proton-Stabilized Photochemically Reversible E/ Z Isomerization of Spiropyrans.

Kortekaas L L Chen J J Jacquemin D D Browne W R WR

The journal of physical chemistry. B 20180611 24

Spiropyrans undergo C<sub>spiro</sub>-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 <sup>1</sup>H NMR spectroscopy as well as UV/vis spectros ...[more]

PMID: 29847129

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