Abstract
A series of N-pyridyl ureas bearing 1,2,4- (1a, 2a, and 3a) and 1,3,4-oxadiazole moiety (1b, 2b, 3b) was prepared and characterized by HRMS, 1H and 13C NMR spectroscopy, as well as X-ray diffraction. The inspection of the crystal structures of (1–3)a,b and the Hirshfeld surface analysis made possible the recognition of the (oxadiazole)···(pyridine) and (oxadiazole)···(oxadiazole) interactions. The presence of these interactions was confirmed theoretically by DFT calculations, including NCI analysis for experimentally determined crystal structures as well as QTAIM analysis for optimized equilibrium structures. The preformed database survey allowed the verification of additional examples of relevant (oxadiazole)···π interactions both in Cambridge Structural Database and in Protein Data Bank, including the cocrystal of commercial anti-HIV drug Raltegravir.
Highlights
Intermolecular interactions involving aromatic rings, primarily arene stacking, impact ligand–protein binding [1,2], the folding of macromolecules [3,4], the solid-state packing of light-emitting and high energetic materials [5,6,7], as well as the productivity of organocatalysts [8,9]
Inspection of the crystallographic data of (1–3)a,b suggests the presence of various noncovalent interactions involving oxadiazole moieties in all studied cases
We have synthesized and crystalized the representative set of six 1,2,4(“a” series, Figure 1) and 1,3,4-oxadiazole (“b” series) based N-pyridyl ureas, which were studied by single-crystal X-ray diffraction
Summary
Intermolecular interactions involving aromatic rings, primarily arene stacking, impact ligand–protein binding [1,2], the folding of macromolecules [3,4], the solid-state packing of light-emitting and high energetic materials [5,6,7], as well as the productivity of organocatalysts [8,9]. Together with high accuracy quantum chemical calculations [18,19,20,21,22], significantly shed light on the area of heterocycle stacking, this field is not fully elucidated and there are many information gaps. To date, such interactions have not been comprehensively investigated for oxadiazoles.
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