Structural Design,\nH‑Bonding Interactions,\nVibrational Properties, Periodic-DFT Calculations, and Antibacterial\nActivity of a Nicotinamide Cocrystal Using Tetradecanoic Acid as a\nCoformer

This paper reports a new nicotinamide cocrystal using\ntetradecanoic\nacid as a coformer by a slow solvent evaporation method in acetone.\nIts structural, thermal, vibrational, and antibacterial properties\nwere characterized and discussed. Single-crystal X-ray diffraction\ndata indicated that the NA–TA cocrystal crystallized in triclinic\nsymmetry and P1̅(Ci) space group, with two formulas per unit\ncell (<i>Z</i> = 2). A detailed analysis of the intermolecular\ninteractions was performed based on Hirshfeld surface and noncovalent\ninteractions. Thermoanalyses revealed that the material is stable\nup to around 128 °C and exhibits endothermic events characteristic\nof solid–liquid phase transition and decomposition. Additionally,\nusing group theory and periodic calculations based on density functional\ntheory (DFT), all inter- and intramolecular modes of the NA–TA\ncocrystal were predicted and assigned. The experimental infrared and\nRaman spectra were well correlated to the spectra calculated via DFT,\nallowing a suitable assignment of the observed vibration modes. Furthermore,\nbiological experiments demonstrated that the cocrystal exhibits promising\nantibacterial activity against Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive) bacteria. An <i>in</i> <i>silico</i> study of the pharmacokinetic profile involving absorption, distribution,\nmetabolism, and excretion parameters was performed to support the\nexperimental findings.