TY - JOUR
T1 - Supramolecular enantiodifferentiating photoisomerization of (Z,Z)-1,3-cyclooctadiene included and sensitized by naphthalene-modified cyclodextrins
AU - Yang, Cheng
AU - Mori, Tadashi
AU - Wada, Takehiko
AU - Inoue, Yoshihisa
PY - 2007/5/16
Y1 - 2007/5/16
N2 - Three naphthalene-modified cyclodextrins (CDs) 3-5 were synthesized as supramolecular chiral photosensitizing hosts for enantiodifferentiating photoisomerization of (Z,Z)-1,3-cyclooctadiene (1ZZ) to its E,Z-isomer (1EZ). In aqueous methanolic solutions, β-CD-based sensitizer 4 binds 1ZZ in its chiral cavity much more strongly than α- and γ-CD homologues 3 and 5. Accelerated, often static, fluorescence quenching of these naphthalene-modified CDs was observed upon inclusion of 1ZZ. The photoisomerization of 1ZZ mediated by 3-5 yielded enantiomeric 1EZ in modest yields. The enantiomeric excesses (ee's) obtained with α- and β-CD-based sensitizers 3 and 4, both of which have relatively small cavities, are less sensitive to temperature, demonstrating the low-entropy nature of the α- and β-CD complexes. In contrast, increasing reaction temperature significantly diminished the product's ee and even caused a switching of enantioselectivity upon photoisomerization sensitized by γ-CD-based 5, revealing that the entropy factor plays a crucial role in the wide cavity of γ-CD.
AB - Three naphthalene-modified cyclodextrins (CDs) 3-5 were synthesized as supramolecular chiral photosensitizing hosts for enantiodifferentiating photoisomerization of (Z,Z)-1,3-cyclooctadiene (1ZZ) to its E,Z-isomer (1EZ). In aqueous methanolic solutions, β-CD-based sensitizer 4 binds 1ZZ in its chiral cavity much more strongly than α- and γ-CD homologues 3 and 5. Accelerated, often static, fluorescence quenching of these naphthalene-modified CDs was observed upon inclusion of 1ZZ. The photoisomerization of 1ZZ mediated by 3-5 yielded enantiomeric 1EZ in modest yields. The enantiomeric excesses (ee's) obtained with α- and β-CD-based sensitizers 3 and 4, both of which have relatively small cavities, are less sensitive to temperature, demonstrating the low-entropy nature of the α- and β-CD complexes. In contrast, increasing reaction temperature significantly diminished the product's ee and even caused a switching of enantioselectivity upon photoisomerization sensitized by γ-CD-based 5, revealing that the entropy factor plays a crucial role in the wide cavity of γ-CD.
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U2 - 10.1039/b615353d
DO - 10.1039/b615353d
M3 - Article
AN - SCOPUS:34248372816
VL - 31
SP - 697
EP - 702
JO - New Journal of Chemistry
JF - New Journal of Chemistry
SN - 1144-0546
IS - 5
ER -