Tetrel bonding stabilized supramolecular dimer versus coordination polymer, obtained from N'-benzoylpyrazine-2-carbohydrazonamide and lead(II) acetate

• A new tetranuclear Pb(II) complex with a pyrazine-based ligand is reported. • Self-assembly is driven by Pb···S and Pb···N tetrel bonding interactions. • DFT/QTAIM analyses confirm perchlorate anions act as supramolecular glue. Combining aqueous Pb(OAc) 2 with a methanolic solution of the ligand N' -benzoylpyrazine-2-carbohydrazonamide ( HL ) yielded two distinct lead(II) complexes. The minor product PbL(OAc)∙H 2 O ( 1 ∙H 2 O) was obtained in 8% yield as orange plates, while the major product Pb 2 L 2 (OAc) 2 n ∙2nMeOH ( 2 ∙2nMeOH) was obtained in 40% yield as orange needles. Both complexes were characterized by elemental analysis, FTIR and 1 H NMR spectroscopy, which confirmed ligand deprotonation. X-ray diffraction revealed distinct architectures: 1 ∙H 2 O features a monodentate acetate and a PbN 3 O 3 coordination core, forming supramolecular dimers via Pb∙∙∙N tetrel bonds. These dimers assemble into 1D chains through hydrogen bonds and π∙∙∙π interactions. In contrast, 2 ∙2nMeOH forms a 1D coordination polymer with bidentate acetates and PbN 5 O 4 coordination cores, which extend into a 2D sheet via an extensive network of tetrel bonds, hydrogen bonds and π∙∙∙π interactions. Furthermore, we employed DFT-based calculations to investigate the nature of the non-covalent interactions governing the crystal packing. The MEP surfaces, along with the QTAIM and NCI plot analyses, were used to characterize the key interactions, including tetrel bonds and electrostatically enhanced π∙∙∙π stacking between the coordinated pyrazine and phenyl rings, as well as secondary hydrogen bonds that complement primary interactions in the selected dimers. The analysis revealed that the Pb∙∙∙N interactions in 2 , which link the monomeric units into a coordination polymer, exhibit characteristics of a strong tetrel bond. This finding allows for the reinterpretation of compound 2 as a supramolecular polymer. We also used 2D plots of the ELF, RDG and Laplacian of the electron density (∇ 2 ρ) to further characterize selected Pb∙∙∙N tetrel bonds as non-covalent interactions involving σ-holes in 1 .