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

The interactions between nicotinamide (NA) and H 2 O were studied using UV–visible spectra (UV–Vis), cyclic voltammetry (CV), nuclear magnetic resonance (NMR), density functional theory (DFT) and atoms in molecules (AIM) analysis. According to the changes of the UV–Vis spectra and the oxidation and reduction potentials in cyclic voltammograms of NA in aqueous solution, it was found that hydrogen bonding occurred between NA and H 2 O molecules. Quantum chemistry calculations and AIM analysis further confirmed the existence of hydrogen bonding between H 2 O molecules and the amide group, the nitrogen atom , and hydrogen atoms on the pyridine ring of NA molecules. In addition, the NMR results demonstrated that the π-π stacking between NA pyridine rings could be formed at higher concentrations.