Coordination-Based Symmetric and Asymmetric Bilayers on Gold Surfaces

Moav, Tamar; Hatzor, Anat; Cohen, Hagai; Libman, Jacqueline; Rubinstein, Israel; Shanzer, Abraham

doi:10.1002/(sici)1521-3765(19980310)4:3<502::aid-chem502>3.3.co;2-2

Cited by 18 publications

(51 citation statements)

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“…Cu Underpotential Deposition (UPD). The coverage of the first monolayer was measured using Cu UPD. , The fraction of gold surface covered by the monolayers was determined by comparing the amount of charge required for Cu UPD at an Au/monolayer electrode with that for a bare Au electrode of the same geometric area, obtained by integration of the respective cathodic UPD peaks. The accuracy of the UPD coverage measurement is estimated at ±5%.…”

Section: Methodsmentioning

confidence: 99%

“…The use of metal ions as coordination links between layers may result in an ordered system wherein the structure as well as electronic and optical properties are determined by the redox activity or other properties of the metal ion chosen. The ligands involved in such a composite structure allow structural versatility and may impart novel photoelectronic behavior. − The use of a conducting support for multilayer construction provides electrical contact to the assembly; hence, metal substrates (especially gold) are often used as substrates in such systems. − …”

Section: Introductionmentioning

confidence: 99%

“…The bilayers can be prepared in a stepwise process, including formation of the SA monolayers of bishydroxamate ligand anchored to the gold via a cyclic disulfide, followed by binding of an 8-coordinating ion and a second layer of bishydroxamate ligand to complete the ion coordination. This process enabled the formation of a variety of compact bilayer structures on gold surfaces …”

Section: Introductionmentioning

confidence: 99%

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Coordination-Controlled Self-Assembled Multilayers on Gold

et al. 1998

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A new kind of multilayers based on metal-ion coordination was constructed on gold surfaces, where molecular layers are successively added using a highly controlled step-by-step procedure. A bifunctional ligand is used as the base layer, bearing a cyclic disulfide group to attach to the gold surface and a bishydroxamate group capable of ion binding. An 8-coordinating metal ion such as Zr4+ or Ce4+ is then coordinated to the bishydroxamate site, followed by exposure to a second ligand possessing four hydroxamate groups. The tetrahydroxamate molecule ligates to the metal ion (bound to the base layer) using two of its four hydroxamate groups and is free to bind a second metal ion at its other end. A sequence of adsorption steps using metal ions and tetrahydroxamate ligands was carried out, resulting in an ordered metal−organic multilayer. Multilayer structures comprising up to 10 tetrahydroxamate/metal ion layers were constructed, with full characterization at each step of multilayer formation using ellipsometry, contact angle measurements, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy. The multilayer morphology and mechanical properties were studied by scanning force microscopy. It is shown that different base ligands induce dramatic differences in the morphology and stiffness of the final multilayer. The possibility to construct segmented multilayers containing Zr4+ and Ce4+ ions at defined locations is presented.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Coordination-Controlled Self-Assembled Multilayers on Gold

et al. 1998

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“…Chemicals : Molecules 1 and 2 (Figure 1) were synthesized as previously reported 44. 52 Zirconium acetylacetonate (Zr(acac) 4 , Fluka, purum) was used without further purification. Chloroform (Biolab, AR) was passed through a column of activated basic alumina.…”

Section: Methodsmentioning

confidence: 99%

Comparison of a colorimetric and a high‐performance liquid chromatography method for the determination of fructan in pasture grasses for horses

Longland¹,

Dhanoa

Harris³

2012

J Sci Food Agric

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“…Synthesis: The synthesis of the active-ester precursor I (Scheme 2) was described earlier. [31] Scheme 2. Synthesis of the precursor I.…”

Section: Methodsmentioning

confidence: 99%

Bidentate Ligation of Heme Analogues; Novel Biomimetics of the Peroxidase Active Site

et al. 2002

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The multifunctional nature of proteins that have iron–heme cofactors with noncovalent histidine linkage to the protein is controlled by the heme environment. Previous studies of these active‐site structures show that the primary difference is the length of the iron‐proximal histidine bond, which can be controlled by the degree of H‐bonding to this histidine. Great efforts to mimic these functions with synthetic analogues have been made for more than two decades. The peroxidase models resulted in several catalytic systems capable of a large range of oxidative transformations. Most of these model systems modified the porphyrin ring covalently by directly binding auxiliary elements that control and facilitate reactivity; for example, electron‐donating or ‐withdrawing substituents. A biomimetic approach to enzyme mimicking would have taken a different route, by attempting to keep the porphyrin ring system unaltered, as close as possible to its native form, and introducing all modifications at or close to the axial coordination sites. Such a model system would be less demanding synthetically, would make it easy to study the effect of a single structural modification, and might even provide a way to probe effects resulting from porphyrin exchange. We introduce here an alternative model system based on these principles. It consists of a two component system: a bis‐imidazolyl ligand and an iron–porphyrin (readily substituted by a hemin). All modifications were introduced only to the ligand that engulfs the porphyrin and binds to the iron's fifth and sixth coordination sites. We describe the design, synthesis, and characterization of nine different model compounds with increased complexity. The primary tool for characterizing the environment of each complex FeIII center was the Extended X‐ray Absorption Fine Structure (EXAFS) measurements, supported by UV/Vis, IR, and NMR spectroscopy and by molecular modeling. Introduction of asymmetry, by attaching different imidazoles as head groups, led to the formation of two axial bonds of different length. Addition of H‐bonds to one of the imidazoles in an advanced model increased this differentiation and expanded the porphyrin ring. These complexes were found to be almost identical in structure to peroxidase active sites. Similarly to the peroxidases and other synthetic models, these compounds stabilize the green, compound I‐like intermediate, and catalyze the oxidation of organic substrates.

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Coordination-Based Symmetric and Asymmetric Bilayers on Gold Surfaces

Cited by 18 publications

References 0 publications

Coordination-Controlled Self-Assembled Multilayers on Gold

Coordination-Controlled Self-Assembled Multilayers on Gold

Comparison of a colorimetric and a high‐performance liquid chromatography method for the determination of fructan in pasture grasses for horses

Bidentate Ligation of Heme Analogues; Novel Biomimetics of the Peroxidase Active Site

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