Constrained photophysics of partially and fully encapsulated charge transfer probe (E)-3-(4-Methylaminophenyl) acrylic acid methyl ester inside cyclodextrin nano-cavities: Evidence of cyclodextrins cavity dependent complex stoichiometry

The polarity sensitive intra-molecular charge transfer (ICT) emission from (E)-3-(4-Methylaminophenyl) acrylic acid methyl ester (MAPAME) is found to show distinct changes once introduced into the nano-cavities of cyclodextrins in aqueous environment. Movement of the molecule from the more polar aqueous environment to the less polar, hydrophobic cyclodextrin interior is marked by the blue shift of the CT emission band with simultaneous fluorescence intensity enhancement. The emission spectral changes on complexation with the α- and β-CD show different stoichiometries as observed from the Benesi–Hildebrand plots. Fluorescence anisotropy and lifetime measurements were performed to probe the different behaviors of MAPAME in aqueous α- and β-CD solutions.

. Modulation of the photoinduced charge transfer reaction of a CT fluorophore inside hydrophobic nanocages of α- and β-cylcodextrins (CD) has been addressed using steady state and time resolved spectroscopy. It is demonstrated that the probe is partial or fully entrapped inside CD cavity and the inclusion complex stoichiometry depends on the cavity size and concentration of CD.Figure optionsDownload as PowerPoint slideHighlights
► Modulation of charge transfer reaction inside cyclodextrin nanocages.
► Cyclodextrin cavity and concentration dependent complexes stoichiometry.
► Shielding of encapsulated probe from external perturbation.
► Partially or fully entrapped probe in cyclodextrin cavity.