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β-diketones compounds exist mainly in 2 forms in equilibrium as we see on schema

# Supplementary Material (ESI) for Chemical Communications

# This journal is � The Royal Society of Chemistry 2004

UV Vis spectra:

β-diketones adopt 2 forms in equilibrium as shown on scheme. The enol form is stabilised by a strong conjugation of π-system and an intramolecular hydrogen bond, whereas the diketo form is destabilised by a dipole-dipole repulsion of the 2 carbonyl groups.

The stabilization of the Enol form by intramolecular hydrogen bonding is more pronounced when no competition exists with the solvent. Hence, keto-enol equilibria of β-diketone compounds are extremely solvent-sensitive, and the proportion of enol form is found to be much greater in apolar or polar aprotic solvents, such as cyclohexane, than in polar protic solvents, such as alcohol or water.

To illustrate the effect of medium polarity on the keto-enol equilibrium, we compared the UV-visible spectra of SDBM in an apolar solvent, Tetrahydrofuran (THF – blue curve) and in a polar protic solvent, H2O (red curve). The peak at 360 nm is only due to enol form and the peak at 280 nm is mainly due to keto form although the enol contributes to the absorption at this point. 1,2 Therefore, UV-visible spectra gives direct information about the environment of the probe.

The mesostructured materials contain 3 distinct regions: 3-5

  • Silica framework
  • Ionic interface of micelles
  • Hydrophobic interior of micelles
  • Spectra of as-prepared thin films exhibit are characteristic of apolar medium (similar to the one observed in THF). This result confirms, in good agreement with 2D-GISAXS data, that β-diketone compounds are localized into the hydrophobic part of micelles (composed by alkyl chains).

    During the thermal treatment, keto peak appears, witnessing the probe medium polarity increase probably promoted by the migration of a fraction of β1 compounds to the ionic interface.

    In fact, during the thermal treatment, we observe several changes:

  • the condensation of silica species leads to a contraction of the inorganic network,
  • the evaporation of water causes a decrease of the thickness of the ionic interface,
  • the complete hydrolysis of siloxane groups of the β1 compounds is achieved (β1 becomes less hydrophobic and more polar).
  • All these changes lead to a migration of β1 compounds to the ionic interface.

    FTIR spectra:

    ������������� (1)������������� Iglesias, E. Journal of Physical Chemistry 1996, 100, 12592.

    ������������� (2)������������� Iglesias, E. J. Chem. Soc., Perkin Trans. 2 1997, 431.

    ������������� (3)������������� Franville, A. C.; Dunn, B.; Zink, J. I. Journal of Physical Chemistry B 2001, 105, 10335.

    ������������� (4)������������� Hernandez, R.; Franville, A.-C.; Minoofar, P.; Dunn, B.; Zink, J. I. Journal of the American Chemical Society 2001, 123, 1248.

    ������������� (5)������������� Minoofar, P. N.; Hernandez, R.; Chia, S.; Dunn, B.; Zink, J. I.; Franville, A.-C. Journal of the American Chemical Society 2002, 124, 14388.

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