Simazine inclusion complexes with cucurbiturils (n = 6-8): experimental and molecular dynamics studies

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Computational Chemistry

Background:

• Simazine (SIM) is a widely used herbicide.
• Cucurbiturils (CBn) are macrocyclic hosts capable of forming inclusion complexes.
• Understanding SIM-CBn interactions is crucial for potential applications in controlled release or environmental remediation.

Purpose of the Study:

• To investigate the formation and stability of Simazine (SIM) inclusion complexes with cucurbit[n]urils (CBn, n=6-8).
• To elucidate the role of host cavity size and non-covalent interactions in complex formation.
• To explore the mechanism and stability of SIM-CBn complexes in both aqueous and solid states.

Main Methods:

• Nuclear Magnetic Resonance (NMR) spectroscopy for solution-state analysis.
• Fourier Transform Infrared (FTIR) spectroscopy and Powder X-ray Diffraction (PXRD) for solid-state characterization.
• Molecular Dynamics (MD) simulations to probe atomic-level interactions and stability.

Main Results:

• Stable inclusion complexes of SIM were formed with CB[7] and CB[8] in aqueous solutions.
• The smaller cavity size of CB[6] precluded the formation of a stable inclusion complex with SIM.
• MD simulations confirmed the high stability of SIM-CB[7] and SIM-CB[8] complexes.
• Both hydrophobic interactions and hydrogen bonding were identified as key stabilizing forces.

Conclusions:

• Cucurbit[7]uril and cucurbit[8]uril are effective hosts for Simazine, forming stable inclusion complexes.
• Cucurbit[6]uril's limited cavity size restricts its ability to complex with Simazine.
• Hydrogen bonding plays a critical role, complementing hydrophobic interactions, in the stabilization of Simazine-cucurbituril complexes.