Structural characterization of a hybrid terpyridine-pyrazine ligand and its one-dimensional Zn^II coordination polymer: a computational approach to conventional and nonconventional intermolecular interactions

The structures of a new hybrid terpyridine-pyrazine ligand, namely 4'-[4-(pyrazin-2-yl)phenyl]-4,2':6',4''-terpyridine (L2), C₂₅H₁₇N₅, and its one-dimensional coordination polymer catena-poly[[bis(acetylacetonato-κ²O,O')zinc]-μ-4'-[4-(pyrazin-2-yl-κN⁴)phenyl]-4,2':6',4''-terpyridine-κN¹], [Zn(C₅H₇O₂)₂(C₂₅H₁₇N₅)]_n or [Zn(acac)₂(L2)]_n (Hacac is acetylacetone), are reported. Packing interactions in both crystal structures are analyzed using Hirshfeld surface and enrichment ratio techniques. For the simpler structure of the monomeric ligand, further studies on the interaction hierarchy using the energy framework approach were made. The result was a complete picture of the intermolecular interaction landscape, which revealed some subtle details, for example, that some weak (at first sight negligible) C-H...N interactions in the structure of free L2 play a relevant role in the crystal stabilization.