N,N′-Di(pyridine-4-yl)-pyridine-3,5-dicarboxamide, a Pincer-Type Tricationic Compound; Synthesis, Crystal Structure, Hirshfeld Surface Analysis, and Computational Chemistry Studies

The synthesis, structure, and spectroscopic characterization of a pincer-type compound; N,N'-di(pyridine-4-yl)-pyridine-3,5-dicarboxamide is described(.) The tricationic pro-ligand (C20H22N5O2)(3+) bearing two pendant alkylated 4-pyridyl arms at the 3,5-positions of the central pyridyl group features three triflate anions (CF3SO3-) in the asymmetric unit. Two of the triflate ligands in the structure are connected to the pincer cation by strong N-H center dot center dot center dot O hydrogen bonds. The central N-methyl moiety is planar to a r.m.s deviation of 0.01, and the two adjacent N-methylpyridine moieties are out of the plane with dihedral angles of 33.62 degrees (3) and 86.08 degrees (3). The molecular packing structure of the compound shows an 18-molecule aggregate in a 3-dimensional supramolecular synthon stabilized by intermolecular N-H center dot center dot center dot O and C-H center dot center dot center dot O contacts. The Hirshfeld surface analysis and fingerprint plots show that the OH/HO contacts resulting from C-H center dot center dot center dot O intermolecular interactions contributed significantly to the overall surface interaction with a total percentage contribution of 35.4%. The pairwise interaction energy calculations were implemented with a Gaussian plugin in Crystal Explorer 17 at the B3LYP/6-31G(d,p) level of theory. Energy profile diagrams and interaction energy values indicate that the crystal structure was stabilized by a combination of electrostatic and dispersion forces in the crystal lattice.