Complexation of spiropyrans with cyclodextrins

Effects of β‐ and γ‐cyclodextrins on the thermal isomerization of 6‐SO 3−‐spiropyran

Yoshimi Sueishi, Tomonori Nishimura

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22 Citations (Scopus)

Abstract

The thermal isomerizations of 1′,3′,3′‐trimethyl‐spiro[2H‐1‐benzopyran‐2,2′‐indoline]‐6‐sulphonic acid (6‐SO 3−‐SP) between its spiro (SP) and merocyanine (MC) forms were followed spectrophotometrically in the presence of cyclodextrins (β‐ and γ‐CDs) at various pressures. From the pressure dependence of the isomerization rate, the activation volumes for the thermal isomerization of 6‐SO 3−‐SP were estimated to be 17·1 cm3 mol−1 for MC → SP and 8·5 cm3 mol−1 for SP → MC. The equilibrium constants (K) for the inclusion complex formation of CDs with 6‐SO 3−‐SP were determined at various pressures. It was found that the stability of the 1:1 inclusion complex between 6‐SO 3−‐SP and CDs decreases in the order β– > γ– > α‐CD. From the pressure dependence of K, the reaction volumes were estimated to be −0·9 cm3 mol−1 for the 6‐SO 3−‐SP–β‐CD system and 4·0 cm3 mol−1 for the 6‐SO 3−‐SP–γ‐CD system. Based on the activation volumes, the structure of the transition state for the thermal isomerization is discussed and an explanation for the effect of CDs on the reaction rate is given. The difference in the reaction volumes for the inclusion complex formation of β‐ and γ‐CDs is explained in terms of the difference in the number of water molecules excluded from the CD cavity.

Original languageEnglish
Pages (from-to)335-340
Number of pages6
JournalJournal of Physical Organic Chemistry
Volume8
Issue number5
DOIs
Publication statusPublished - 1995

Fingerprint

Cyclodextrins
Isomerization
Complexation
isomerization
inclusions
pressure dependence
Chemical activation
activation
Equilibrium constants
Reaction rates
reaction kinetics
cavities
acids
Molecules
Acids
spiropyran
Hot Temperature
Water
water
spiro-merocyanine

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Organic Chemistry

Cite this

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title = "Complexation of spiropyrans with cyclodextrins: Effects of β‐ and γ‐cyclodextrins on the thermal isomerization of 6‐SO 3−‐spiropyran",
abstract = "The thermal isomerizations of 1′,3′,3′‐trimethyl‐spiro[2H‐1‐benzopyran‐2,2′‐indoline]‐6‐sulphonic acid (6‐SO 3−‐SP) between its spiro (SP) and merocyanine (MC) forms were followed spectrophotometrically in the presence of cyclodextrins (β‐ and γ‐CDs) at various pressures. From the pressure dependence of the isomerization rate, the activation volumes for the thermal isomerization of 6‐SO 3−‐SP were estimated to be 17·1 cm3 mol−1 for MC → SP and 8·5 cm3 mol−1 for SP → MC. The equilibrium constants (K) for the inclusion complex formation of CDs with 6‐SO 3−‐SP were determined at various pressures. It was found that the stability of the 1:1 inclusion complex between 6‐SO 3−‐SP and CDs decreases in the order β– > γ– > α‐CD. From the pressure dependence of K, the reaction volumes were estimated to be −0·9 cm3 mol−1 for the 6‐SO 3−‐SP–β‐CD system and 4·0 cm3 mol−1 for the 6‐SO 3−‐SP–γ‐CD system. Based on the activation volumes, the structure of the transition state for the thermal isomerization is discussed and an explanation for the effect of CDs on the reaction rate is given. The difference in the reaction volumes for the inclusion complex formation of β‐ and γ‐CDs is explained in terms of the difference in the number of water molecules excluded from the CD cavity.",
author = "Yoshimi Sueishi and Tomonori Nishimura",
year = "1995",
doi = "10.1002/poc.610080503",
language = "English",
volume = "8",
pages = "335--340",
journal = "Journal of Physical Organic Chemistry",
issn = "0894-3230",
publisher = "John Wiley and Sons Ltd",
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T1 - Complexation of spiropyrans with cyclodextrins

T2 - Effects of β‐ and γ‐cyclodextrins on the thermal isomerization of 6‐SO 3−‐spiropyran

AU - Sueishi, Yoshimi

AU - Nishimura, Tomonori

PY - 1995

Y1 - 1995

N2 - The thermal isomerizations of 1′,3′,3′‐trimethyl‐spiro[2H‐1‐benzopyran‐2,2′‐indoline]‐6‐sulphonic acid (6‐SO 3−‐SP) between its spiro (SP) and merocyanine (MC) forms were followed spectrophotometrically in the presence of cyclodextrins (β‐ and γ‐CDs) at various pressures. From the pressure dependence of the isomerization rate, the activation volumes for the thermal isomerization of 6‐SO 3−‐SP were estimated to be 17·1 cm3 mol−1 for MC → SP and 8·5 cm3 mol−1 for SP → MC. The equilibrium constants (K) for the inclusion complex formation of CDs with 6‐SO 3−‐SP were determined at various pressures. It was found that the stability of the 1:1 inclusion complex between 6‐SO 3−‐SP and CDs decreases in the order β– > γ– > α‐CD. From the pressure dependence of K, the reaction volumes were estimated to be −0·9 cm3 mol−1 for the 6‐SO 3−‐SP–β‐CD system and 4·0 cm3 mol−1 for the 6‐SO 3−‐SP–γ‐CD system. Based on the activation volumes, the structure of the transition state for the thermal isomerization is discussed and an explanation for the effect of CDs on the reaction rate is given. The difference in the reaction volumes for the inclusion complex formation of β‐ and γ‐CDs is explained in terms of the difference in the number of water molecules excluded from the CD cavity.

AB - The thermal isomerizations of 1′,3′,3′‐trimethyl‐spiro[2H‐1‐benzopyran‐2,2′‐indoline]‐6‐sulphonic acid (6‐SO 3−‐SP) between its spiro (SP) and merocyanine (MC) forms were followed spectrophotometrically in the presence of cyclodextrins (β‐ and γ‐CDs) at various pressures. From the pressure dependence of the isomerization rate, the activation volumes for the thermal isomerization of 6‐SO 3−‐SP were estimated to be 17·1 cm3 mol−1 for MC → SP and 8·5 cm3 mol−1 for SP → MC. The equilibrium constants (K) for the inclusion complex formation of CDs with 6‐SO 3−‐SP were determined at various pressures. It was found that the stability of the 1:1 inclusion complex between 6‐SO 3−‐SP and CDs decreases in the order β– > γ– > α‐CD. From the pressure dependence of K, the reaction volumes were estimated to be −0·9 cm3 mol−1 for the 6‐SO 3−‐SP–β‐CD system and 4·0 cm3 mol−1 for the 6‐SO 3−‐SP–γ‐CD system. Based on the activation volumes, the structure of the transition state for the thermal isomerization is discussed and an explanation for the effect of CDs on the reaction rate is given. The difference in the reaction volumes for the inclusion complex formation of β‐ and γ‐CDs is explained in terms of the difference in the number of water molecules excluded from the CD cavity.

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