Thermodynamic study of β-cyclodextrin-dye inclusion complexes using gradient flow injection technique and molecular...

Area of Science:

• Analytical Chemistry
• Supramolecular Chemistry

Background:

• Beta-cyclodextrin (β-CD) forms inclusion complexes with various guest molecules, including dyes.
• Understanding the stoichiometry and stability of these complexes is crucial for applications.

Purpose of the Study:

• To develop and validate a rapid gradient flow injection technique coupled with diode array spectrophotometry for studying β-CD-dye inclusion complexes.
• To determine the stability constants (log Kf) and stoichiometry of complexes formed between β-CD and several model dyes.

Main Methods:

• Gradient flow injection analysis with diode array spectrophotometry.
• Spectrophotometric titration data analyzed using model-based multivariate methods.
• Singular value decomposition (SVD) for model selection and noise reduction.
• Molecular modeling to predict guest molecule conformation and interactions within the β-CD cavity.

Main Results:

• The developed method successfully determined the stoichiometry and stability constants for β-CD complexes with methyl orange, fluorescein, phenol red, PAR, and crystal violet.
• Stoichiometric ratios (β-CD:dye) and log Kf values were accurately calculated.
• Molecular modeling provided insights into the specific interactions and orientations of guest molecules within the β-CD cavity.

Conclusions:

• The gradient flow injection technique offers a simple, fast, and reliable alternative to classical titration methods for studying β-CD inclusion complexes.
• This approach minimizes human interference and enhances understanding of host-guest interactions through integrated molecular modeling.