Synthesis, crystal structure and thermal investigation of molecular salts of (R)-1-phenylethanamine combined with quantum chemical studies

Abstract

Molecular salts (R)-1-phenylethanaminium oxalate (1), (R)-1-phenylethanaminium 2-carboxy-4,6-dinitrophenolate (2) and (R)-1-phenylethanaminium 4-methylbenzenesulfonate (3) were synthesized and characterized by1H, 13C{1H} NMR and FT-IR spectra. The structures of [C8NH12]2+[C2O4]2- (1), [C8NH12]+[C7H3N2O7]− (2)and [C8NH12]+[C7H7SO3]− (3) were confirmed by single crystal X-ray diffraction which belonging to monoclinic, triclinic and orthorhombic crystal systems with the Flack parameter (x) -0.3(8), 0.9(6) and 0.05(10) respectively. The salt 1 forms a three dimensional structure comprising N-H···O hydrogen bonds and C-H···π interactions, while, in 2, strong O-H···O and N-H···O hydrogen bonds along with C-H···O and π···π interactions lead to a three-dimensional architecture, and in 3, the N-H···O hydrogen bonds generate one-dimensional ribbon framework. The qualitative and quantitative confirmation of the presence of various interactions in 1, 2 and 3 were made by Hirshfeld surface analyses. Thermogravimetric analysis was performed to know their thermal stability. Density functional theory was performed to outline the optimized structure, the frontier molecular orbitals, reactive parameters, and molecular electrostatic potential. Natural bonding orbitals (NBO) analysis was carried out to study the donor-acceptor atom interactions contributing to the stabilization of the crystal structure. The topology analysis (QTAIM and NCI) gave further insights into understanding the attractive and repulsive types of interactions exhibited by the molecule.