Anion driven tetrel bonding dictated supramolecular architectures of lead(ii) with a zwitterionic form of polydentate N′-(piperidine-1-carbonothioyl)picolinohydrazonamide

Abstract

Two novel supramolecular heteroleptic complexes [Pb2L2(NO3)2]n (1) and {[Pb3L3](ClO4)3}n·3.25nH2O (2·3.25nH2O), obtained from N′-(piperidine-1-carbonothioyl)picolinohydrazonamide (HL) and Pb(NO3)2 or Pb(ClO4)2 in aqueous methanol are reported. A crucial role of the auxiliary ligand (NO3−vs. ClO4−) was revealed as a driving force for the formation of the resulting architecture of complexes, which, in turn, are dictated by the formation of tetrel bonds. Complex 1 is constructed from heteroleptic dinuclear centrosymmetric species [Pb2L2(NO3)2], which, in turn, are formed from the heteroleptic mononuclear symmetry related [PbL(NO3)] units, linked through a pair of bonds formed between the metal cations and the thioamide nitrogen atoms. The metal cations form a weaker tetrel bond with the symmetry related nitrate atoms, yielding a 1D polymeric chain structure. These chains are interlinked through N-H⋯O hydrogen bonds, formed between the covalently coordinated nitrate oxygen atom and the NH2 hydrogen atom, yielding a 2D supramolecular architecture. Complex 2·3.25nH2O is constructed from the trinuclear species [Pb3L3](ClO4)3. The trinuclear cation is constructed from three [PbL]+ cations interlinked through two Pb-S and two Pb-N bonds, formed with the thiocarbonyl sulfur atoms and the amide nitrogen atoms. The cations [Pb3L3]3+ are interlinked through two Pb-N and two Pb-S bonds yielding a 1D supramolecular polymeric cationic chain {[Pb3L3]3+}n. The two metal cations corresponding to two [PbL]+ units, linked through a pair of the Pb-S bonds, are additionally bridged by two oxygen atoms of one of the perchlorate anions with the formation of two Pb⋯O tetrel bonds. The coordination spheres of the metal cations are filled by one of the oxygen atoms of two different perchlorate anions with the formation of tetrel bonds. One of these perchlorates also forms the N-H⋯O hydrogen bond within the trinuclear unit [Pb3L3](ClO4)3. 1D supramolecular chains {[Pb3L3]3+}n are interlinked through a myriad of hydrogen bonds formed by the perchlorate anions and crystallized water molecules. The tetrel bonds involving the counterions (Pb⋯O) have been also analysed by DFT calculations via a MEP surface plot and 2D maps of electron localization function (ELF), Laplacian of electron density (∇2ρ) and reduced density gradient (RDG), confirming their noncovalent nature. © 2024 The Royal Society of Chemistry.