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    Anion driven tetrel bonding dictated supramolecular architectures of lead(ii) with a zwitterionic form of polydentate N′-(piperidine-1-carbonothioyl)picolinohydrazonamide
    (Royal society of chemistry, 2024) Mahmoudi, Ghodrat; Garcia-Santos, Isabel; Castineiras, Alfonso; Fernandez-Vazquez, Roi; Gargari, Masoumeh Servati; Gomila, Rosa M.; Frontera, Antonio
    Two novel supramolecular heteroleptic complexes [Pb2L2(NO3)(2)](n) (1) and {[Pb3L3](ClO4)(3)}(n)3.25nH(2)O (23.25nH(2)O), 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 & ctdot;O hydrogen bonds, formed between the covalently coordinated nitrate oxygen atom and the NH2 hydrogen atom, yielding a 2D supramolecular architecture. Complex 23.25nH(2)O 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 & ctdot;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 & ctdot;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 & ctdot;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 (del(2)rho) and reduced density gradient (RDG), confirming their noncovalent nature.
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    Structural diversity and tetrel bonding significance in lead(ii) complexes with pyrazoylisonicotinoylhydrazone and varied anionic co-ligands
    (Royal Soc Chemistry, 2024) Mahmoudi, Ghodrat; Garcia-Santos, Isabel; Fernandez-Vazquez, Roi; Gomila, Rosa M.; Castineiras, Alfonso; Doustkhah, Esmail; Zangrando, Ennio
    Four lead(ii) complexes featuring pyrazoylisonicotinoylhydrazone ligand paired with various anionic co-ligands (azido, thiocyanato, nitrito, and nitrato) were synthesized and thoroughly examined using structural, analytical, and spectroscopic techniques. These ligands, in their mono-deprotonated state, bind to the lead(ii) ion in a tridentate manner through two nitrogen atoms and one oxygen atom. Single-crystal X-ray crystallography revealed the capacity of these molecular complexes to form larger aggregates influenced by the nature of the anion attached to the metal center. In every complex, the lead atom adopts a hemidirectional coordination environment, making it geometrically suited for tetrel bond formation. The crystal structures demonstrate that lead atoms engage in notably short interactions with nitrogen atoms, distances that are shorter than the sum of their van der Waals radii yet exceed the sum of their covalent radii. These tetrel bonds play a pivotal role in weaving the monomeric into self-assembled dimers or extended supramolecular 1D polymers. The formation and characteristics of these intriguing supramolecular structures observed in the solid state of each complex were further explored and validated through density functional theory (DFT) calculations and several computational tools like MEP, NCIPlot, QTAIM, and ELF methods.