研究目的
Investigating the host-guest interaction of a 4-methylumbelliferone derivative with cucurbit[7]uril in aqueous solution, including the formation of inclusion complexes, binding constants, and changes in photophysical properties.
研究成果
The interaction between 3ED4MU and CB7 forms a 1:1 inclusion complex with high binding constants (1.75×10^5 M^-1 in ground state, 2.30×10^5 M^-1 in excited state). This complex stabilizes the zwitterionic species and significantly alters the acid-base equilibria in the excited state, enabling the neutral form to exist up to pH 8. The findings suggest potential applications in modulating the properties of hydroxycoumarins for various uses.
研究不足
The study is limited to aqueous solutions and specific solvents (DMSO, dioxane). The interaction may not generalize to other hosts or conditions. Potential optimizations include exploring a wider range of pH values or other cucurbituril hosts.
1：Experimental Design and Method Selection:
The study involved steady-state and time-resolved fluorescence spectroscopy, 1H NMR spectroscopy, and absorption spectroscopy to investigate the interaction between 3ED4MU and CB7. Theoretical models for binding constants and acid-base equilibria were employed.
2：Theoretical models for binding constants and acid-base equilibria were employed.
Sample Selection and Data Sources:
2. Sample Selection and Data Sources: Samples included 3ED4MU and CB7 purchased from Sigma-Aldrich, dissolved in aqueous solutions at various pH values, and organic solvents like DMSO and dioxane. Concentrations were around 10 μM.
3：List of Experimental Equipment and Materials:
Equipment included a Cary 5000 spectrophotometer for absorption, Horiba-Fluoromax spectrofluorimeter for fluorescence, time-correlated single-photon-timing setups for fluorescence decays, Bruker Avance DPX 400 MHz spectrometer for NMR, and a Jenway pH-meter for pH measurements. Materials included 3ED4MU, CB7, solvents (water, DMSO, dioxane), and pH adjustment chemicals (HClO4, NaOH, DCl, NaOD).
4：Experimental Procedures and Operational Workflow:
Solutions were prepared at specific pH values. Titrations were performed by adding increasing amounts of CB7 to 3ED4MU solutions. Absorption, fluorescence, and NMR spectra were recorded. Fluorescence decays were measured at different wavelengths and pH values, and data were deconvoluted using appropriate methods.
5：Data Analysis Methods:
Binding constants were calculated using non-linear least-square fitting of absorbance and fluorescence intensity changes. Fluorescence decays were analyzed with multi-exponential fitting. NMR shifts were interpreted to infer complex formation.
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