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Abstract
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Three novel coordination compounds, namely [Pb(L)Cl]2 (1), [Pb(L)(NO2)]2.2(CH3OH) (2), and [Pb6(L)4(Cl)2(NCS)6].2(CH3OH) (3), where HL is 1-(pyridine-2-yl)aminoethylene-4-hexamethyleneimine thiosemicarbazide, have been synthesized and structurally characterized by elemental analysis, FTIR, 1H NMR spectroscopy, and single-crystal X-ray diffraction. The structural analysis reveals that the supramolecular architectures are modulated by the specific anions used during synthesis, leading to the formation of dimeric and hexanuclear units that further assemble into polymeric structures. A comprehensive DFT study at the PBE0-D3/def2-TZVP level was conducted to analyze the variety of non-covalent interactions that stabilize the solid-state structures, with a focus on tetrel bonding. Molecular electrostatic potential (MEP) surfaces identify three distinct sigma-holes at the Pb(II) centers, providing an electronic rationale for the observed directional tetrel bonds. Notably, compound 1 exhibits an unprecedented like-like Pbsingle bondPb contact that contributes to the formation of 1D polymeric chains. This intermetallic interaction was characterized using QTAIM and NCIplot methods, revealing its attractive and van der Waals nature, with a computed dimerization energy of −4.4 kcal/mol. These findings highlight the high coordination flexibility of Pb(II) and the role of tetrel bonding as structural linker in directing complex supramolecular assemblies.
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