Polyaromatic Hydrocarbon Inclusion Complexes with 2-Hydroxylpropyl-β/γ-Cyclodextrin: Molecular Dynamic Simulation and...

Area of Science:

• Supramolecular Chemistry
• Analytical Chemistry
• Computational Chemistry

Background:

• Polycyclic Aromatic Hydrocarbons (PAHs) are environmental pollutants.
• Cyclodextrins (CDs) are widely used for guest molecule complexation.
• Hydroxypropyl-modified cyclodextrins (HP-CDs) offer enhanced solubility and complexation properties.

Purpose of the Study:

• To investigate the formation and stability of inclusion complexes between HP-β-CD/HP-γ-CD and PAHs (Phenanthrene, Anthracene, Benz(a)pyrene, Fluoranthene).
• To elucidate the complexation mechanism and driving forces using spectroscopic and computational methods.
• To compare the complexation efficiency of HP-β-CD and HP-γ-CD with different PAHs.

Main Methods:

• Fluorescence spectroscopy for complex characterization.
• Proton Nuclear Magnetic Resonance (1H NMR) spectroscopy for structural analysis.
• Molecular Dynamics (MD) simulations to investigate inclusion mechanisms and stability.

Main Results:

• 1:1 guest-to-host complexes were predominantly observed.
• Stability constants varied significantly among different PAHs and hosts, with Benz(a)pyrene and Fluoranthene forming the strongest complexes with HP-β-CD.
• MD simulations confirmed the formation of stable exclusion complexes, with van der Waals, hydrophobic forces, and C-H⋯π interactions as key stabilizing factors.
• Flexible hydroxypropyl arms influenced the inclusion mode, leading to stable exclusion complexes rather than full encapsulation.

Conclusions:

• HP-β-CD and HP-γ-CD form stable exclusion complexes with PAHs.
• The complexation is driven by non-covalent interactions, primarily van der Waals forces and hydrophobic effects.
• Spectroscopic and MD simulation results are in good agreement, providing a comprehensive understanding of the complexation process.