Deciphering supramolecular synthons in OXYMA-B salts: Crystallographic characterization and theoretical evaluation of hydrogen bond networks

• Four new crystal structures of OXYMA-B salts have been discovered, prepared and their crystal structures analyzed using DFT calculations • OXYMA-B salts structures showed that directional N–H···O bonds consistently contribute the most to the stability of the assemblies, with ancillary contacts playing a secondary yet supportive role • The electron-rich nature of the OXYMA-B anion provides multiple sites for H-bond acceptance, leading to diverse supramolecular synthons Four new crystal structures of OXYMA-B in its anionic form have been synthesized and structurally characterized via single-crystal X-ray diffraction. The new salts incorporate protonated amine-based cations including 1-phenylpiperazine (1PP), 1,4-dioxa-8-azaspiro[4.5]decane (DASD), ethylenediamine (ETDA), and pyrrolidine (Pyr), which function as efficient hydrogen bond (H-bond) donors. The electron-rich nature of the OXYMA-B anion provides multiple sites for H-bond acceptance, leading to diverse supramolecular synthons including R 1 2 (5), R 1 2 (6), R 4 2 (8) and R 4 3 (12). The theoretical component of this study is based on density functional theory (DFT) calculations to dissect and characterize the individual H-bonded synthons using the quantum theory of atoms in molecules (QTAIM) framework. Additionally, interaction energies of discrete H-bonds have been quantified to rationalize their strength and directional preferences, showing that directional NH···O bonds contribute the most to the stability of the assemblies, with ancillary contacts playing a secondary but supportive role. The total interaction energies range from –34.0 to –50.0 kcal/mol, underscoring the critical role of hydrogen bonding in dictating the supramolecular architectures. This combined experimental–computational approach sheds light on the structural determinants driving supramolecular organization in OXYMA-B-based salts and highlights their potential for crystal engineering applications.