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    A joint action of coordination, hydrogen and tetrel bonds toward a new 2D coordination polymer of lead(II) perchlorate and N'-isonicotinoylpyrazine-2-carbohydrazonamide
    (Elsevier b.v., 2025) Mahmoudi, Ghodrat; Garcia-Santos, Isabel; Safin, Damir A.; Fernández-Vazquez, Roi; Eftekhari-sis, Bagher; Gomila, Rosa M.; Frontera, Antonio
    A new 2D coordination polymer of lead(II) with N'-isonicotinoylpyrazine-2-carbohydrazonamide (HL) was readily produced by reacting with an equimolar amount of Pb(ClO4)2 in aqueous methanol solution. The resulting metallocomplex was isolated in the form of yellow prism-like crystals of {[PbL](ClO4)center dot 0.4H2O}n, suitable for a single crystal X-ray diffraction analysis, and was studied using FTIR and 1H NMR spectroscopy, and single crystal X-ray diffraction. The oxygen atoms of the ClO4- anion are disordered over two positions with an occupancy ratio of 60 % to 40 %. The minor occupancy is accompanied with the crystal water molecule, which, thus, yields 0.4 molecule per one [PbL](ClO4). Analysis of the crystal structure of the discussed complex allowed to reveal the formation of a dinuclear dimeric species [Pb2L2]2+ from the [PbL]+ cations through a pair of Pb center dot center dot center dot N tetrel bonds formed with the amide nitrogen atoms, which is further reinforced by a pair of pi center dot center dot center dot pi interactions formed between the pyrazine and pyridine rings. Three oxygen atoms from two perchlorate anions complete the coordination sphere (N4O4) of the metal cation, yielding an anionic {[PbL]2(ClO4)4}2- species, which is stabilized by a pair of N-H center dot center dot center dot O hydrogen bonds, formed by one of the NH2 hydrogen atoms and one of the oxygen atoms of the major occupancy of an adjacent perchlorate anion. In the crystal packing, the cations [PbL]+ are linked through the Pb-N coordination bonds formed with the pyridine nitrogen atom, yielding a 1D cationic coordination polymers {[PbL]n}n+ of a zig-zag structure, which, in turn, are linked into a 2D coordination network. The topology of this 2D network disclosed a uninodal 3-connected net of fes with the point symbol of (4 center dot 82). 2D layers are stacked with each other int a 3D supramolecular framework, which voids are filled by the perchlorate anions and crystal water molecules. DFT calculations have been performed to characterize the Pb center dot center dot center dot N/O tetrel bonding interactions along with more conventional hydrogen bonding that are crucial in the generation of the coordination polymer and its final 3D architecture.
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    Synthesis and characterization of a series of lead complexes with (pyrazinyl)benzohydrazone ligand and theoretical studies of their supramolecular dimerization in solid state
    (Elsevier b.v., 2025) Mahmoudi, Ghodrat; Garcia-Santos, Isabel; Novikov, Alexander S.; Kornilov, Dmitry A.; Fernández-Vazquez, Roi; Castiñeiras, Alfonso; Zangrando, Ennio
    We have synthesized a series of lead complexes with pyrazinyl-4-methylbenzoylhydrazone (HPyz) and different anions as ancillary ligands, namely [Pb(HPyz)Cl2] (1), [Pb(Pyz)(NO2)] (2), [Pb(Pyz)(NO3)(H2O)] (3), [Pb(Pyz) (NO2)0.5(NO3)0.5(H2O)] (4), and [Pb(Pyz)(SCN)(H2O)] (5). These complexes have been characterized by 1H NMR, IR, and X-ray diffraction techniques. All the complexes show a comparable coordination mode of the organic ligand while the supramolecular crystal structure is addressed by the anions and coordinated water molecules when present. In fact, the solid state is characterized by it-stacking interactions between pyrazine and phenyl rings. In particular, inspection of X-ray data reveals dimerization of centrosymmetric related species of these lead complexes via various noncovalent interactions. To assess the nature of these intermolecular interactions, the Hirshfeld surface analysis and DFT calculations, followed by topological analysis of the electron density distribution within the QTAIM approach and NCI analysis, have been carried out for the model structures based on the experimental X-ray diffraction analysis data. The Hirshfeld surface analysis for the X-ray structures reveals that in all cases crystal packing is determined primarily by intermolecular contacts involving hydrogen atoms. The QTAIM analysis of model structures demonstrates the presence of bond critical points for various intermolecular interactions responsible for the supramolecular dimerization of the studied lead complexes in solid state.