Non-covalent Reduced Density Gradient Research Articles

Noncovalent interactions in N-methylurea crystalline hydrates

Abstract Urea and its derivatives play a significant role in modern organic chemistry and find application in various fields. This study presents the results of investigations of N-methylurea crystalline hydrates. Initial N-methylurea and its crystalline hydrates have been examined by FTIR spectroscopy and X-ray diffraction analysis. It has been found that the incorporation of water molecules into N-methylurea crystals leads to a shift of intensity peaks in both the FTIR spectra and X-ray diffraction patterns. Methylurea crystalline hydrates in the gaseous phase have been additionally explored within the density functional theory at the B3LYP/6-31+G(d,p) level and the theory of atoms in molecules. The nature of water and methylurea molecular interactions via hydrogen bonds have been studied using the electron localization function and noncovalent reduced density gradient. The thermodynamic and nonlinear optical properties of methylurea crystalline hydrate have been determined. The atoms in molecules, electron localization functions, and localized orbital locator topological analyses have been carried out to elucidate the nature of hydrogen bonds in methylurea crystalline hydrates.

Hydrogen bonds interactions in biuret-water clusters: FTIR, X-ray diffraction, AIM, DFT, RDG, ELF, NLO analysis

In this work, we studied intermolecular aqueous clusters of biuret, an important urea derivative. FTIR showed an increase in the intensity of absorption bands when water molecules are introduced into the biuret. X-ray diffraction analysis showed that the introduction of water molecules into the biuret structure significantly increases the intensity of the bands on the diffraction patterns in the range from 14 to 65 2˚⊖. Aqueous biuret clusters have also been studied in the gas phase by theoretical methods: density functional theory and Atoms in Molecules (AIM) using the DFT level B3LYP/6–31 + G (d, p). The nature of molecular interactions between water and biuret through hydrogen bonds was also investigated using the electron localization function (ELF) and non-covalent reduced density gradient (NC-RDG). The thermodynamic and Non-linear optical properties of biuret-water clusters were performed also.

Toxic potential of Poly-hexamethylene biguanide hydrochloride (PHMB): A DFT, AIM and NCI analysis study with solvent effects

In the current study, the toxic material Poly-hexamethylene biguanide hydrochloride (PHMB) has been characterized by UV–Visible and infrared spectroscopy in different solvent environments. The nature of the molecular interactions between solvent molecules and PHMB via hydrogen bonds has been investigated using the Atoms in Molecules (AIM) and non-covalent reduced density gradient (NC-RDG) analyses. Intermolecular interactions are further supported by the Natural Bond Orbital (NBO) analysis, which was carried out to provide information about the delocalization of charge and energy density of the atoms. The OH···Cl and NH···Cl hydrogen bond types of interaction in solvent complexes have indicated weak hydrogen bonds. Moreover, we studied the endocrine disrupting potential of PHMB by using VirtualToxLab technology.

Intermolecular hydrogen bonds interactions in water clusters of ammonium sulfamate: FTIR, X-ray diffraction, AIM, DFT, RDG, ELF, NBO analysis

Ammonium sulfamate is an important sulfamic acid derivative. It has found wide application as a herbicide, fire-resistant agent, etc. In this work, we investigated intermolecular aqueous clusters of ammonium sulfamate. According to FTIR spectroscopy data, the introduction of water molecules increases the intensity of the absorption bands in the FTIR spectra. In addition, there is a significant increase in the intensity of absorption bands (by a factor of 6) in the range of 3550–3200 cm−1, which correspond to intermolecular interactions of OH groups. It was shown by X-ray diffraction that the introduction of water molecules into the structure of ammonium sulfamate significantly changes the intensities of the absorption bands in the diffraction patterns. The geometry optimization of aqueous clusters of ammonium sulfamate with a content of water molecules from 1 to 15 was carried out in the gas phase using the DFT B3LYP/6-311 ++ G (d, p) level. The nature of the molecular interactions between water and ammonium sulfamate via hydrogen bonds has been investigated using the Atoms in Molecules (AIM), Electron Localization Function (ELF) and non-covalent reduced density gradient (NC-RDG) analyses. Thermodynamic and NLO properties of ammonium sulfamate-water clusters have been carried outusing the DFT/B3LYP/6-31+G(d,p) methodology.

Solvation of lithium ion in helium clusters: Structural properties and relative stabilities

Structural study and relative stabilities of Li+-doped helium clusters Li+Hen (n = 1–18) has been reported in this work using two theoretical protocols. The first one is based on the basin-hopping optimization technique, where the total energy of each cluster is described by an additive model describing Li+-He and He–He interactions. The second one is the DFT calculations, in which the initial structures are generated by ABCluster algorithm and CALYPSO software. The CSA shape was found where the first solvation shell is completed at n = 10. The relative stabilities of Li+Hen (n = 1–18) clusters have been discussed based on the variation of the binding energy, second-order difference in energy, fragmentation energy and HOMO-LUMO energy gap as a function of the cluster size. The results showed that Li+He10 is the most stable cluster. The dipole moment is calculated and showed the polar character of the Li+Hen clusters. Finally, the interatomic interactions have been examined topologically by the means of AIM and non-covalent reduced density gradient (NC-RDG) analyses.