In nature, hydrogen bonding is a common physical occurrence that has a significant impact on the surroundings of anthocyanins. Water molecules will create hydrogen bonds with anthocyanin molecules in various configurations, but the characteristics of these hydrogen bonds will change. Varied hydrogen bonding characteristics have varied impacts on solvent solutions. This research analyzes the differences in hydrogen bonding qualities caused by different methyl structures, as well as the underlying explanations. In this study, the cyanidin (Cy) and peonidin (Pn) structures of anthocyanin molecules were calculated in various stable hydrogen bond configurations using density functional theory B3LYP/6-31G(d,p). combined with information from the Infrared Spectroscopy (IR) spectrum, Atoms In Molecules (AIM) analysis, interaction energy E, and intermolecular hydrogen bond length. Determine the hydrogen bond structure that is the most stable by analyzing it, as well as the effects of replacing the hydroxyl group with a methyl group and any potential underlying causes.

On the basis of density functional theory (DFT), the geometry and infrared spectrum of the (AlP) 8 cluster have been calculated under external electric fields (EEFs). In addition, on the basis of time-dependent DFT, the ultravioletvisible absorption spectra, oscillator strengths, wavelengths, and hole-electron orbits of the first 20 excited states have been calculated. Under EEFs, the energy of (AlP) 8 gradually decreases, the dipole moment increases, and the molecular configuration significantly changes. In the infrared spectrum, the vibration frequency corresponding to the stretching vibration of the Al-P bond decreases, and a red shift occurs. With increasing EEF, the infrared spectrum splits and shows an obvious Stark effect; the ultraviolet absorption intensity is enhanced, and the molecular excitation energy decreases. Additionally, the excitation wavelength increases with increasing EEF. It is conclusively shown that the (AlP) 8 cluster is easily excited under an EEF. Separation of the holes and electrons of the (AlP) 8 cluster is obvious. Theoretical investigation of the spectra and excitation properties of (AlP) 8 is an important step toward a comprehensive understanding of the effects of EEFs on the molecular structure, stability, and dynamics.

Tea polyphenols are essential components that give tea its medicinal properties. Methanol and water are frequently used as solvents in the extraction of polyphenols. Hydrogen‐bonding interactions are significant in the extraction reaction. Density functional theory (DFT) techniques were used to conduct a theoretical investigation on the hydrogen‐bonding interactions between methanol or water and epicatechin, an abundant polyphenol found in tea. After first analyzing the epicatechin monomer's molecular geometry and charge characteristics, nine stable epicatechin (EC) H2O/CH2OH complex geometries were discovered. The presence of hydrogen bonding in these improved structures has been proven. The calculated hydrogen bond structures are very stable, among which the hydrogen bond bonded with a hydroxyl group has higher stability. The nine complex structures’ hydrogen bonds were thought to represent closed‐shell‐type interactions. The interaction energy with 30O‐31H on the epicatechin benzene ring is the strongest in the hydrogen bond structure. While the other hydrogen bonds were weak in strength and mostly had an electrostatic nature, the hydrogen bonds between the oxygen atoms in H2O or CH2OH and the hydrogen atoms of the hydroxyl groups in epicatechin were of moderate strength and had a covalent character. Comparing the changes in the hydrogen bond structure vibration peak, the main change in concentration peak is the hydrogen bond vibration peak in the complex. Improved the study on the hydrogen bond properties of CH2OH and H2O of EC.