Synthesis and Characterization of Iron Nitrosyl Thiolate Complexes; Studies of Nitrite Reduction by Iron Thiolate Complexes
Author: 歐翰璋
Publisher:
Published: 2017
Total Pages: 95
ISBN-13:
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Author: 歐翰璋
Publisher:
Published: 2017
Total Pages: 95
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DOWNLOAD EBOOKAuthor: 郭晉廷
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Published: 2012
Total Pages: 84
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DOWNLOAD EBOOKAuthor: 吳宗翰
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Published: 2017
Total Pages: 107
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DOWNLOAD EBOOKAuthor: 陳南傑
Publisher:
Published: 2011
Total Pages: 90
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DOWNLOAD EBOOKAuthor: Laima Maria Baltusis
Publisher:
Published: 1979
Total Pages: 366
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DOWNLOAD EBOOKAuthor: Wen-Feng Liaw
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Published: 1989
Total Pages: 232
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DOWNLOAD EBOOKAuthor: Yubin Kwon
Publisher:
Published: 2016
Total Pages: 0
ISBN-13:
DOWNLOAD EBOOKThe activation of small molecules has been studied by the scientific field for many decades as it plays a key role in nature such as photosynthesis and respiration. Many of these reactions are catalyzed by metalloenzymes in nature where the transfer of electrons and protons are coupled for the reaction to move forward. Noncovalent interactions in the secondary coordination sphere of metalloenzymes play an important role in determining the activity and selectivity. Hydrogen bonds are the most common noncovalent interactions that metalloenzymes utilize to control the reactivity in the secondary coordination sphere. Therefore, it is important to develop compounds and catalysts that can move both protons and electrons. Recent studies have been done by several groups on the mechanism of nitrite reduction. Based on those findings, we developed a series of iron (II) pyridinediimine (PDI) complexes that contain pendant bases, with varying pKa values, located in the secondary coordination sphere. These ligands were synthesized, coordinated to iron (II) and reduced under carbon monoxide (CO) to store electrons within the ligand scaffold. These reduced complexes were then protonated to form hydrogen bonds and fine tune the reactivity. These PDI complexes that are capable of storing both electrons and protons were investigated to functionally mimic the metalloenzyme nitrite reductase. To date, the mechanism of nitrite reduction remains unknown. In an attempt to determine how nitrite binds to the metal of our PDI complex, we synthesized a dinitrosyl iron complex. The synthesis of this complex should help to determine the mechanism of nitrite reduction.
Author: Miguel Angel Camacho Fernandez
Publisher:
Published: 2010
Total Pages: 238
ISBN-13: 9781124548357
DOWNLOAD EBOOKAbstract: Recent developments involving the physiological implications of nitric oxide have spurred an intense interest in transition metal nitrosyl complexes, especially those that mimic the structures of biologically active metal nitrosyl complexes. In order to get insights on the electronic configuration, molecular orbital's interaction, and explain spectroscopic (NMR, EPR, and IR) observations, Density Functional Theory calculations were carried out on three series of metal nitrosyl complexes, Fe(NO)2 (P(OCH3)3)[eta]2-TCNE, [Fe2([mu]-RS)2(NO)4], and [Fe(NO)2(Im-H)]4 . The unusually high rotation barrier observed by NMR was explained through fragment analysis of Fe(NO)2 and TCNE. In addition, the difference of the g values between the reduced form of Roussin's red Esters and the typical dinitrosyl iron complexes is explained, for the first time, by of the difference in unpaired electron distributions between the two types of complexes, which provides the theoretical basis for the use of g value as a spectroscopic tool to differentiate these biologically active complexes.
Author: American Chemical Society. Meeting
Publisher:
Published: 1986
Total Pages: 1350
ISBN-13:
DOWNLOAD EBOOKAuthor: Jennifer Hess
Publisher:
Published: 2012
Total Pages:
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DOWNLOAD EBOOKThe significant role that nitric oxide plays in human physiology is linked to the ability of NO to bind to iron forming mono-nitrosyl iron complexes. Protein-bound and low-molecular-weight dinitrosyl iron complexes (DNICs) are known to form in excess NO. Studies of such biological DNICs have relied on their paramagnetism and characteristic EPR signal of g value of 2.03. It has been suggested that DNICs act in vivo as NO storage (when protein-bound) and transfer agents (when released by, for example, free cysteine). Biological DNICs, mainly resulting from iron-sulfur cluster degradation, are difficult to extract and isolate, thereby preventing their full characterization. Thus, development of synthetic DNICs is a promising approach to model and better understand the formation and function of biological DNICs, the scope of donor ligands that might coexist with Fe(NO)2 units, the redox levels of bio-DNICs, and establish other spectroscopic techniques appropriate for characterization. A series of N-heterocyclic carbene (NHC) and imidazole (Imid) complexes has been characterized as mimics of histidine-containing DNICs. The pseudo-tetrahedral L2Fe(NO)2 complexes have NO stretching frequencies and redox potentials that suggest the NHCs are slightly better donors than Imids, however the two types of ligands have similar steric properties. Both the EPR-active, {Fe(NO)2}9 and the EPR-silent, {Fe(NO)2}10 states can be accessed and stabilized by the NHC. Nitric oxide transfer studies have shown that only the {Fe(NO)2}9 complexes are capable of transferring NO to a suitable NO trapping agent. Deprotonation of the distal nitrogen functionality in the imidazolate ligands of [(Imidazole)2Fe(NO)2]- leads to aggregation forming molecular squares of {Fe(NO)2}9 units bridged by the imidazolates. These interesting tetrameric complexes are examined by X-ray diffraction, EPR, and Mössbauer studies. The paramagnetic tetrameric complexes have multiple redox events observed by cyclic voltammetry. Mössbauer spectral data of the tetrameric complexes are compared with Mössbauer data obtained for a series of NHC-containing DNICs. Iron and cobalt-containing mononitrosyl N2S2 model complexes of the nitrile hydratase enzyme active site demonstrate sulfur-based reactivity resulting in the formation of polymetallic complexes. In all cases, shifts in the nitrosyl stretching frequencies demonstrate substantial transfer of electron density from the (NO)M(N2S2) moiety to the metal-acceptor site.