Hydrogen bonding and π-π stacking in nicotinamide/H₂O mixtures

Area of Science:

• Physical Chemistry
• Computational Chemistry
• Molecular Spectroscopy

Background:

• Nicotinamide (NA) is a vital biomolecule with diverse roles.
• Understanding NA's interactions in aqueous solutions is crucial for its applications.
• Previous studies have explored NA's properties, but detailed interaction mechanisms require further investigation.

Purpose of the Study:

• To elucidate the molecular interactions between nicotinamide (NA) and water (H₂O).
• To investigate the role of hydrogen bonding and π-π stacking in NA-water systems.
• To provide a comprehensive understanding of NA's behavior in aqueous environments.

Main Methods:

• UV-visible spectroscopy (UV-Vis) to monitor spectral changes.
• Cyclic voltammetry (CV) to assess redox potentials.
• Nuclear magnetic resonance (NMR) spectroscopy for structural insights.
• Density functional theory (DFT) and Atoms in Molecules (AIM) analysis for theoretical confirmation.

Main Results:

• UV-Vis and CV data indicated hydrogen bonding between NA and water molecules.
• DFT and AIM analyses confirmed hydrogen bonds involving NA's amide group, pyridine nitrogen, and ring hydrogens.
• NMR results revealed π-π stacking interactions between NA pyridine rings at elevated concentrations.

Conclusions:

• Hydrogen bonding is a primary interaction between nicotinamide and water.
• π-π stacking contributes to NA aggregation in concentrated solutions.
• These findings enhance the understanding of nicotinamide's solution chemistry and behavior.