First crystalline salt of 1,1-bis-(carboxymethylthio)-1-phenylethane: synthesis, crystal structure, Hirshfeld surface analysis, and computational study

The reaction of 1,1-bis-(carboxymethylthio)-1-phenylethane with piperidine was conducted in an acetone solution at a molar ratio of the initial components of 1:2. As a result, a new compound was obtained: piperidinium-1,1-bis-(carboxymethylthio)-1-phenylethane, characterized by FT-IR. The crystal structure of the synthesized compound is structurally elucidated via single crystal XRD technique, indicating that a H-atom is transferred from half of the piperidinium-1,1-bis-(carboxymethylthio)-1-phenylethane part to the piperidine ring and the structure is a salt in nature. N-H & ctdot;O and C-H & ctdot;O bondings contribute to the stability and enforcement of crystal packing; further assessment is supported via Hirshfeld surface analysis, considering interatomic contacts. We employed density functional theory (DFT)-based computations along with molecular dynamics (MD) simulations in a systematic manner, aiming for the investigation of the stabilizing interactions and electronic characteristics of the molecular ionic compound. The structural framework is notably stabilized by dual N-H & centerdot;& centerdot;& centerdot;O hydrogen bonding, originating from piperidine rings positioned on either side of the central fragment. Electronic structure analysis revealed intermolecular charge transfer characteristics through HOMO-LUMO orbital distributions, complemented by TD-DFT studies of excited state behavior. Furthermore, ab initio MD simulations at 300 K conclusively demonstrated the ionic compound's robust kinetic and dynamic stability.