Preparation, Crystal Structure, Supramolecular Assembly, and DFT Studies of Two Organic Salts Bearing Pyridine and Pyrimidine

The effective preparation of two new pyrimidine- andpyridine-basedorganic crystalline salts with substituted acidic moieties (i.e.,(Z)-4-(naphthalen-2-ylamino)-4-oxobut-2-enoic acid(DCNO) and 2-hydroxy-3,5-dinitrobenzoic acid (PCNP)) using methanol as a solvent has been reported. These molecularsalts have ionic interactions that are responsible for their structuralstabilization in their solid-state assemblies. The crystal structuresof DCNO and PCNP were determined by thesingle-crystal X-ray diffraction (SCXRD) technique. The SCXRD studyinferred that cations and anions are strongly packed due to N-H & BULL;& BULL;& BULL;O,N-H & BULL;& BULL;& BULL;N, and C-H & BULL;& BULL;& BULL;O noncovalentinteractions in DCNO, whereas in PCNP, N-H & BULL;& BULL;& BULL;Nnoncovalent interactions are absent. The noncovalent interactionsin both organic crystalline salts were comprehensively investigatedby Hirshfeld surface analysis. Further, a detailed density functionaltheory (DFT) study of both compounds was performed. The optimizedstructures of both compounds supported the existence of the H-bondingand weak dispersion interactions in the synthesized organic crystallinesalt structures. Both compounds were shown to have large and noticeablydifferent HOMO/LUMO energy gaps. The atomic charge analysis resultssupported the SCXRD and HSA results, showing the formation of intermolecularnoncovalent interactions in both organic crystalline salts. The resultsof the natural bond orbital (NBO) analysis confirmed the existenceof (relatively weak) noncovalent interactions between the cation andanion moieties of their organic crystalline salts. The global reactivityparameters (GRPs) analysis showed that both organic crystalline salts'compounds should be quite thermodynamically stable and that DCNO should be less reactive than PCNP. For bothcompounds, the molecular electrostatic potential (MEP) analysis resultssupport the existence of intermolecular electrostatic interactionsin their organic crystalline salts.

Automated summary

The effective preparation of two new pyrimidine- and pyridine-based organic crystalline salts with substituted acidic moieties using methanol as a solvent has been reported. These molecular salts have ionic interactions responsible for their structural stabilization in solid-state assemblies. The crystal structures of the salts were determined and their noncovalent interactions were investigated.