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207Pb NMR Spectroscopy

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Ali Morsali – One of the best experts on this subject based on the ideXlab platform.

  • Syntheses and characterization of Pb(trz) n X2 (X = CH3COO−, NCS−, and n = 1, 2) complexes, and crystal structure of [Pb(trz)2(MeOH)](ClO4)2·H2O
    Journal of Coordination Chemistry, 2005
    Co-Authors: Ali Morsali

    Abstract:

    Lead(II) complexes with 2,4,6-tris(2-pyridyl)-1,3,5-triazine (trz) have been synthesized using a direct synthetic method and characterized by IR and 207Pb NMR Spectroscopy and CHN elemental analysis. The structure of [Pb(trz)2(MeOH)](ClO4)2·H2O was confirmed by X-ray crystallography. Single-crystal X-ray data for [Pb(trz)2(MeOH)](ClO4)2·H2O show the complex to be monomeric with the Pb having an unsymmetrical seven-coordinate geometry, coordinated by six nitrogen atoms of the trz ligands and one oxygen atom of MeOH. The arrangement of the ligands in the [Pb(trz)2(MeOH)](ClO4)2·H2O complex exhibits a coordination gap around the Pb(II), occupied possibly by a stereoactive lone pair of electrons on lead(II); the coordination around the lead atoms is hemidirected. Email: morsali_a@yahoo.com

  • One-Dimensional Holodirected Lead(II) Coordination Polymer, [Pb(μ2-TPPZ)(NO3)(ClO4)]n (TPPZ = 2, 3, 5, 6–tetra(2-pyridyl)pyrazine)
    Zeitschrift für anorganische und allgemeine Chemie, 2005
    Co-Authors: Ali Morsali, Ali Ramazani

    Abstract:

    A lead(II) complex with 2,3,5,6-tetra(2-pyridyl)pyrazine (TPPZ), nitrate, and perchlorate ligands has been synthesized and characterized by CHN elemental analysis and IR and 207Pb NMR Spectroscopy. The single crystal X-ray data of the [Pb2(μ-TPPZ)2(NO3)2(ClO4)2] compound show that the complex is a one-dimensional coordination polymer and that the Lead atom has a less-common, ten-coordinate holodirected geometry.

  • Syntheses and characterization of some new mixed-ligand lead(II) complexes, Pb(en)(CH3COO)X (X = NCS−, or ); Crystal Structure of [Pb(en)(CH3COO)(NO3)] n (en = ethane-1,2-diamine)
    Journal of Coordination Chemistry, 2004
    Co-Authors: Ali Morsali, Jafar Abedini

    Abstract:

    Lead(II) complexes with ethane-1,2-diamine (en) containing two different anions, [Pb(en)(CH3COO)X] (X = NCS−, or ), have been synthesized and characterized by CHN elemental analysis, IR, 1H NMR, 13C NMR and 207Pb NMR Spectroscopy. Single crystal X-ray data for [Pb(en)(NO3)(CH3COO)] show the complex to be polymeric. The Pb atom has an unsymmetrical five-coordinate geometry and the weak interaction of lead(II) with oxygen atoms of adjacent molecule produces polymeric units in the solid state. The en ligand and counter ions in this complex exhibit a coordination gap around the Pb(II) ion, occupied possibly by a stereoactive lone pair of electrons on lead(II), that may be affected by intermolecular hydrogen bonding.

Xiao-ming Chen – One of the best experts on this subject based on the ideXlab platform.

  • A new lead(II) complex of 2,2′-bipyridine, acetate and thiocyanate ligands: synthesis, characterization and crystal structure of [Pb(bpy)(NCS)(CH3COO)] n
    Journal of Coordination Chemistry, 2004
    Co-Authors: Ali Morsali, Xiao-ming Chen

    Abstract:

    A new lead(II) complex of 2,2′-bipyridine (bpy), acetate and thiocyanate has been synthesized and characterized by C H N elemental analysis, IR, 1H NMR, 13C NMR and 207PbNMR Spectroscopy. The structure of [Pb(bpy)(NCS)(CH3COO)] n was confirmed by X-ray crystallography. Single-crystal X-ray data show the complex to be a one-dimensional polymer as a result of thiocyanate ligand bridging with the basic repeating monomeric units [Pb(bpy)(NCS)(CH3COO)]. The Pb atom has an unsymmetrical five-coordinate geometry, being coordinated by two nitrogen atoms of bpy, two oxygen atoms of the acetate and one nitrogen atom of the thiocyanate anion. The arrangement of the bpy, acetate and nitrate ligands exhibits a coordination gap around the Pb(II) ion, occupied possibly by a stereoactive lone pair of electrons on lead(II), and the coordination around the lead atoms is hemidirected. There are π–π stacking interactions between the parallel aromatic rings.

  • a new lead ii complex of 2 2 bipyridine acetate and thiocyanate ligands synthesis characterization and crystal structure of pb bpy ncs ch3coo n
    Journal of Coordination Chemistry, 2004
    Co-Authors: Ali Morsali, Xiao-ming Chen

    Abstract:

    A new lead(II) complex of 2,2′-bipyridine (bpy), acetate and thiocyanate has been synthesized and characterized by C H N elemental analysis, IR, 1H NMR, 13C NMR and 207PbNMR Spectroscopy. The structure of [Pb(bpy)(NCS)(CH3COO)] n was confirmed by X-ray crystallography. Single-crystal X-ray data show the complex to be a one-dimensional polymer as a result of thiocyanate ligand bridging with the basic repeating monomeric units [Pb(bpy)(NCS)(CH3COO)]. The Pb atom has an unsymmetrical five-coordinate geometry, being coordinated by two nitrogen atoms of bpy, two oxygen atoms of the acetate and one nitrogen atom of the thiocyanate anion. The arrangement of the bpy, acetate and nitrate ligands exhibits a coordination gap around the Pb(II) ion, occupied possibly by a stereoactive lone pair of electrons on lead(II), and the coordination around the lead atoms is hemidirected. There are π–π stacking interactions between the parallel aromatic rings.

  • Heteropolynuclear Sodium(I) Lead(II) Complex: Crystal and Molecular Structure of a Novel 3-D Polymer, [(en)Pb(μ3-ONO)2Na(μ3-ONO)2Na(μ-O2ClO2)Na]n
    Helvetica Chimica Acta, 2004
    Co-Authors: Ali Morsali, Xiao-ming Chen

    Abstract:

    A novel 3D polymeric heteropolynuclear sodium(I) lead(II) complex containing different ligands, [NaPb(ClO4)(en)(NO2)2] was synthesized and characterized by elemental analysis and IR, and 1H-, 13C-, and 207PbNMR Spectroscopy. The single-crystal X-ray data of [NaPb(ClO4)(en)(NO2)2]n established that the complex is a three-dimensional polymer, [(en)Pb(μ3-ONO)2Na(μ3-ONO)2Na(μ-O2ClO2)Na]n. The Pb and Na atoms have four- and eight-coordinate geometry, respectively. The lone pair of electrons at the PbII atom is ‘stereochemically active’.

Vincent L. Pecoraro – One of the best experts on this subject based on the ideXlab platform.

  • Lead(II) Binding in Natural and Artificial Proteins.
    Metal ions in life sciences, 2017
    Co-Authors: Virginia M. Cangelosi, Leela Ruckthong, Vincent L. Pecoraro

    Abstract:

    This article describes recent attempts to understand the biological chemistry of lead using a synthetic biology approach. Lead binds to a variety of different biomolecules ranging from enzymes to regulatory and signaling proteins to bone matrix. We have focused on the interactions of this element in thiolate-rich sites that are found in metalloregulatory proteins such as Pbr, Znt, and CadC and in enzymes such as δ-aminolevulinic acid dehydratase (ALAD). In these proteins, Pb(II) is often found as a homoleptic and hemidirectic Pb(II)(SR)3- complex. Using first principles of biophysics, we have developed relatively short peptides that can associate into three-stranded coiled coils (3SCCs), in which a cysteine group is incorporated into the hydrophobic core to generate a (cysteine)3 binding site. We describe how lead may be sequestered into these sites, the characteristic spectral features may be observed for such systems and we provide crystallographic insight on metal binding. The Pb(II)(SR)3- that is revealed within these α-helical assemblies forms a trigonal pyramidal structure (having an endo orientation) with distinct conformations than are also found in natural proteins (having an exo conformation). This structural insight, combined with 207Pb NMR Spectroscopy, suggests that while Pb(II) prefers hemidirected Pb(II)(SR)3- scaffolds regardless of the protein fold, the way this is achieved within α-helical systems is different than in β-sheet or loop regions of proteins. These interactions between metal coordination preference and protein structural preference undoubtedly are exploited in natural systems to allow for protein conformation changes that define function. Thus, using a design approach that separates the numerous factors that lead to stable natural proteins allows us to extract fundamental concepts on how metals behave in biological systems.

  • Pb-207 NMR Spectroscopy Reveals that Pb(II) Coordinates with Glutathione (GSH) and Tris Cysteine Zinc Finger Proteins in a PbS3 Coordination Environment
    Journal of inorganic biochemistry, 2011
    Co-Authors: Kosh P. Neupane, Vincent L. Pecoraro

    Abstract:

    Abstract 207Pb NMR Spectroscopy can be used to monitor the binding of Pb(II) to thiol rich biological small molecules such as glutathione and to zinc finger proteins. The UV/visible (UV/Vis) absorption band centered at 334 nM and the observed 207Pb signal in 207Pb NMR (δ ~ 5750 ppm) indicate that glutathione binds Pb(II) in a trigonal pyramidal geometry (PbS3) at pH 7.5 or higher with a 1:3 molar ratio of Pb(II) to GSH. While previous studies using UV/Vis and extended X-ray absorption fine structure (EXAFS) Spectroscopy were interpreted to show that the zinc binding domain from HIV nucleocapsid protein (HIV-CCHC) binds Pb(II) in a single PbS3 environment, the more sensitive 207Pb NMR spectra (at pH 7.0, 1:1 molar ratio) provide compelling evidence for the presence of two PbS3 structures (δ – 5790 and 5744 ppm), one of which is more stable at high temperatures. It has previously been proposed that the HIV-CCHH peptide does not fold properly to afford a PbS2N motif, because histidine does not bind to Pb(II). These predictions are confirmed by the present studies. These results demonstrate the applicability of 207Pb NMR to biomolecular structure determination in proteins with cysteine binding sites for the first time.

  • Probing a Homoleptic PbS3 Coordination Environment in a Designed Peptide Using 207Pb NMR Spectroscopy: Implications for Understanding the Molecular Basis of Lead Toxicity
    Angewandte Chemie (International ed. in English), 2010
    Co-Authors: Kosh P. Neupane, Vincent L. Pecoraro

    Abstract:

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