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    A lead(II)-N′-isonicotinoylpyrazine-2-carbohydrazonamide complex system as a converter of aerial carbon dioxide to carbonate under electrochemical conditions with the formation of a single-component white light-emitting phosphor
    (Royal society of chemistry, 2024) Mahmoudi, Ghodrat; Garcia-Santos, Isabel; Labisbal, Elena; Castineiras, Alfonso; Alizadeh, Vali; Gomila, Rosa M.; Frontera, Antonio; Safin, Damir A.
    In this contribution, a novel binuclear heteroleptic complex [Pb2L2(CO3)]2CH(3)CN2MeOH (12CH(3)CN2MeOH) is reported, which was fabricated by electrochemical oxidation of a lead anode under an ambient atmosphere in a CH3CN : MeOH solution of N '-isonicotinoylpyrazine-2-carbohydrazonamide (HL). The CO32- anion was produced from the conversion of aerial CO2 by the Pb2+-L complex system under electrochemical conditions. In the structure of 1, ligand L exhibits a tridentate pincer-like N,N ',O-coordination mode, while the CO32- anion exhibits a tetradentate bridging coordination mode with one of the oxygen atoms exhibiting a bridging mu-coordination mode. The metal cations in the structure of 1 are in a five-membered N2O3 coordination environment, formed by covalent bonds. The molecular structure of 12CH(3)CN2MeOH is stabilized by a pair of intermolecular Pb & ctdot;N tetrel bonds formed with one of the NH2 nitrogen atoms of an adjacent complex molecule and with the acetonitrile nitrogen atom, and one Pb & ctdot;O tetrel bond formed with the carbonyl oxygen atom of the other adjacent complex molecule, yielding a 2D supramolecular sheet. This sheet is further stabilized by intermolecular N-H & ctdot;N-acetonitrile and N-H & ctdot;O-carbonate hydrogen bonds and pi(Pyrazine)& ctdot;pi(Pyridine) interactions. The optical properties of the complex were revealed by UV-vis spectroscopy and spectrofluorimetry in MeOH. It was established that the described complex is emissive upon excitation at 340 nm with a broad band from about 500 nm to 780 nm with a maximum at similar to 580 nm, accompanied by a shoulder at similar to 620 nm. The CIE-1931 chromaticity coordinates of (0.28, 0.36) fall within the white gamut of the chromaticity diagram. Thus, complex 1 is a single-component white light-emitting phosphor.
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    A Nanosized Porous Supramolecular Lead(II)-N′-phenyl(pyridin-2-yl)methylene-N-phenylthiosemicarbazide Aggregate, Obtained Under Electrochemical Conditions
    (American Chemical Society, 2024) Mahmoudi, Ghodrat; Garcia Santos, Isabel; Labisbal, Elena; Castineiras, Alfonso; Alizadeh, Vali; Gomila, Rosa M.; Frontera, Antonio; Safin, Damir A.
    A novel nanosized porous supramolecular nonanuclear complex [Pb9(HL)12Cl2(ClO4)](ClO4)3·15H2O·a(solvent) (1·15H2O·a(solvent)) is reported that was synthesized by electrochemical oxidation of a Pb anode under the ambient conditions in a CH3CN:MeOH solution of N′-phenyl(pyridin-2-yl)methylene-N-phenylthiosemicarbazide (H2L), containing [N(CH3)4]ClO4 as a current carrier. The supramolecular aggregate of 1 is enforced by a myriad of Pb···S tetrel bonds (TtBs) established with the thiocarbonyl sulfur atoms of adjacent species, which have been also analyzed by DFT calculations via 2D maps of ELF, Laplacian and RDG properties. Moreover, Pb···Cl TtBs with the central Cl- anion, and Pb···O TtBs with the three oxygen atoms of the ClO4- anion, were revealed. Notably, the molecular structure of 1 differs significantly from that recently reported by us [Pb2(HL)2(CH3CN)(ClO4)2]·2H2O (2·2H2O), which was obtained using a conventional synthetic procedure by reacting Pb(ClO4)2 with H2L in the same CH3CN:MeOH solution, thus highlighting a crucial role of the electrochemical conditions. The optical characteristics of the complex were investigated using UV-vis spectroscopy and spectrofluorimetry in methanol. The complex was found to be emissive when excited at 304 nm, producing a broad emission band ranging from approximately 420 to 600 nm with multiple peaks. The CIE-1931 chromaticity coordinates, calculated as (0.33, 0.24), suggest that the emission lies in the white region of the chromaticity diagram. Further investigation is needed to fully characterize the origin of this emission. © 2024 The Authors. Published by American Chemical Society.
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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.