Non-covalent interactions in binary mixtures of sulfamic acid and methylurea

This study investigates the nature and strength of non-covalent interactions in binary mixtures of methylurea (MeU) and sulfamic acid (SA) using a combination of experimental and computational approaches. The electronic properties of methylurea (MeU) and its clusters with sulfamic acid molecules (MeU-n∙SA, n = 1–5), such as molecular electrostatic potential surface (MEPS) and frontier molecular orbitals (FMOs), were studied using density functional theory (DFT) at the B3LYP-D3/6–311++G(d,p) level. The topological parameters of the electron density at the critical points of hydrogen bonding in the MeU-n∙SA (n = 1–5) molecular clusters and the nature of the hydrogen bonding were evaluated using Atoms in Molecules (AIM), Reduced Density Gradient (RDG), and Electron Localized Functions (ELF) analyses. The results of topological analysis showed that the O–H…O and N–H…O hydrogen bonds are responsible for the stability of the geometry of the MeU-n∙SA (n = 1–5) molecular clusters. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) were used to study the influence of non-covalent interactions on the vibrational spectra and crystal structure of the binary mixture of MeU and SA.