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Combination of Scanning Probe Microscopy and Coordination Chemistry: Structural and Electronic Study of Bis(methylbenzimidazolyl)ketone and Its Iron Complex.

ABSTRACT: Here, we report the bulk synthesis of [FeII(BMBIK)Cl2] bearing the redox noninnocent bis(methylbenzimidazolyl)ketone (BMBIK) ligand and the synthesis of the similar complex [FeI(BMBIK)]+ on a Au(111) surface using lateral manipulation at the atomic level. Cyclic voltammetry and scanning tunneling spectroscopy are shown to be useful techniques to compare the coordination compound in solution with the one on the surface. The total charge, as well as the oxidation and spin state of [FeI(BMBIK)]+, are investigated by comparison of the shape of the lowest unoccupied molecular orbital (LUMO), visualized by tunneling through the LUMO, with theoretical models. The similar reduction potentials found for the solution and surface compounds indicate that the major effect of lowering the LUMO upon coordination of BMBIK to the iron center is conserved on the surface. The synthesis and analysis of [FeI(BMBIK)]+ using scanning tunneling microscopy, scanning tunneling spectroscopy, and atomic force microscopy are the first steps toward mechanistic studies of homogeneous catalysts with redox noninnocent ligands at the single molecule level.

SUBMITTER: Folkertsma E

PROVIDER: S-EPMC5410654 | biostudies-literature | 2017 Apr

REPOSITORIES: biostudies-literature

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Combination of Scanning Probe Microscopy and Coordination Chemistry: Structural and Electronic Study of Bis(methylbenzimidazolyl)ketone and Its Iron Complex.

Folkertsma Emma E van der Lit Joost J Di Cicco Francesca F Lutz Martin M Klein Gebbink Robertus J M RJM Swart Ingmar I Moret Marc-Etienne ME

ACS omega 20170410 4

Here, we report the bulk synthesis of [FeII(BMBIK)Cl2] bearing the redox noninnocent bis(methylbenzimidazolyl)ketone (BMBIK) ligand and the synthesis of the similar complex [FeI(BMBIK)]+ on a Au(111) surface using lateral manipulation at the atomic level. Cyclic voltammetry and scanning tunneling spectroscopy are shown to be useful techniques to compare the coordination compound in solution with the one on the surface. The total charge, as well as the ...[more]

PMID: 28474011

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Project description:This Account focuses on the coordination chemistry of the microbial iron chelators called siderophores. The initial research (early 1970s) focused on simple analogs of siderophores, which included hydroxamate, catecholate, or hydroxycarboxylate ligands. The subsequent work increasingly focused on the transport of siderophores and their microbial iron transport. Since these are pseudo-octahedral complexes often composed of bidentate ligands, there is chirality at the metal center that in principle is independent of the ligand chirality. It has been shown in many cases that chiral recognition of the complex occurs. Many techniques have been used to elucidate the iron uptake processes in both Gram-positive (single membrane) and Gram-negative (double membrane) bacteria. These have included the use of radioactive labels (of ligand, metal, or both), kinetically inert metal complexes, and Mössbauer spectroscopy. In general, siderophore recognition and transport involves receptors that recognize the metal chelate portion of the iron-siderophore complex. A second, to date less commonly found, mechanism called the siderophore shuttle involves the receptor binding an apo-siderophore. Since one of the primary ways that microbes compete with each other for iron stores is the strength of their competing siderophore complexes, it became important early on to characterize the solution thermodynamics of these species. Since the acidity of siderophores varies significantly, just the stability constant does not give a direct measure of the relative competitive strength of binding. For this reason, the pM value is compared. The pM, like pH, is a measure of the negative log of the free metal ion concentration, typically calculated at pH 7.4, and standard total concentrations of metal and ligand. The characterization of the electronic structure of ferric siderophores has done much to help explain the high stability of these complexes. A new chapter in siderophore science has emerged with the characterization of what are now called siderocalins. Initially found as a protein of the human innate immune system, these proteins bind both ferric and apo-siderophores to inactivate the siderophore transport system and hence deny iron to an invading pathogenic microbe. Siderocalins also can play a role in iron transport of the host, particularly in the early stages of fetal development. Finally, it is speculated that the molecular targets of siderocalins in different species differ based on the siderophore structures of the most important bacterial pathogens of those species.

Dataset Information

Combination of Scanning Probe Microscopy and Coordination Chemistry: Structural and Electronic Study of Bis(methylbenzimidazolyl)ketone and Its Iron Complex.

Publications

Combination of Scanning Probe Microscopy and Coordination Chemistry: Structural and Electronic Study of Bis(methylbenzimidazolyl)ketone and Its Iron Complex.

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