Phthalocyanine as a redox-active platform for organometallic chemistry

2018 ◽  
Vol 54 (15) ◽  
pp. 1829-1832 ◽  
Author(s):  
Wen Zhou ◽  
Daniel B. Leznoff
Keyword(s):  
Organometallic Chemistry ◽  
Oxidation States ◽  
Metal Centre ◽  
Carbon Chemistry ◽  
Alkyl Complexes ◽  
Redox Active ◽  
Wide Range ◽  
Ring Oxidation

The first structurally characterized phthalocyanine (Pc)-based PcM-aryl, PcM–alkynyl, and PcM–Wittig complexes (with any metal centre), and the first PcCr–alkyl complexes spanning three chromium and two Pc-ring oxidation states are presented, illustrating that this classical, redox-active macrocycle can support a wide range of metal–carbon chemistry.

General Cyclopropane Assembly via Enantioselective Redox-Active Carbene Transfer to Aliphatic Olefins

2018 ◽  
Author(s):  
Marc Montesinos-Magraner ◽  
Matteo Costantini ◽  
Rodrigo Ramirez-Contreras ◽  
Michael E. Muratore ◽  
Magnus J. Johansson ◽  
...  
Keyword(s):  
Total Synthesis ◽  
Asymmetric Synthesis ◽  
Chemical Space ◽  
Synthetic Approach ◽  
Asymmetric Cyclopropanation ◽  
Redox Active ◽  
Wide Range ◽  
Leaving Group ◽  
Stereoelectronic Properties ◽  
Carbene Transfer

Asymmetric cyclopropane synthesis currently requires bespoke strategies, methods, substrates and reagents, even when targeting similar compounds. This limits the speed and chemical space available for discovery campaigns. Here we introduce a practical and versatile diazocompound, and we demonstrate its performance in the first unified asymmetric synthesis of functionalized cyclopropanes. We found that the redox-active leaving group in this reagent enhances the reactivity and selectivity of geminal carbene transfer. This effect enabled the asymmetric cyclopropanation of a wide range of olefins including unactivated aliphatic alkenes, enabling the 3-step total synthesis of (–)-dictyopterene A. This unified synthetic approach delivers high enantioselectivities that are independent of the stereoelectronic properties of the functional groups transferred. Our results demonstrate that orthogonally-differentiated diazocompounds are viable and advantageous equivalents of single-carbon chirons<i>.</i>

scholarly journals Bioinspired organometallic chemistry

2002 ◽  
Vol 74 (1) ◽  
pp. 115-122 ◽  
Author(s):  
Lanny S. Liebeskind ◽  
Jiri Srogl ◽  
Cecile Savarin ◽  
Concepcion Polanco
Keyword(s):  
Organometallic Chemistry ◽  
Refractory Metal ◽  
Redox Active ◽  
The Stability ◽  
New Procedures ◽  
Sulfur Containing ◽  
Insight Into

Given the stability of the bond between a mercaptide ligand and various redox-active metals, it is of interest that Nature has evolved significant metalloenzymatic processes that involve key interactions of sulfur-containing functionalities with metals such as Ni, Co, Cu, and Fe. From a chemical perspective, it is striking that these metals can function as robust biocatalysts in vivo, even though they are often "poisoned" as catalysts in vitro through formation of refractory metal thiolates. Insight into the nature of this chemical discrepancy is under study in order to open new procedures in synthetic organic and organometallic chemistry.

scholarly journals Non-Stoichiometric Redox Active Perovskite Materials for Solar Thermochemical Fuel Production: A Review

Catalysts ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 611 ◽  
Author(s):  
Anita Haeussler ◽  
Stéphane Abanades ◽  
Julien Jouannaux ◽  
Anne Julbe
Keyword(s):  
Carbon Dioxide ◽  
Solar Energy ◽  
Energy Conversion ◽  
Operating Conditions ◽  
Solar Fuel ◽  
Fuel Production ◽  
Concentrated Solar Energy ◽  
Redox Active ◽  
Conversion Rates ◽  
Wide Range

Due to the requirement to develop carbon-free energy, solar energy conversion into chemical energy carriers is a promising solution. Thermochemical fuel production cycles are particularly interesting because they can convert carbon dioxide or water into CO or H2 with concentrated solar energy as a high-temperature process heat source. This process further valorizes and upgrades carbon dioxide into valuable and storable fuels. Development of redox active catalysts is the key challenge for the success of thermochemical cycles for solar-driven H2O and CO2 splitting. Ultimately, the achievement of economically viable solar fuel production relies on increasing the attainable solar-to-fuel energy conversion efficiency. This necessitates the discovery of novel redox-active and thermally-stable materials able to split H2O and CO2 with both high-fuel productivities and chemical conversion rates. Perovskites have recently emerged as promising reactive materials for this application as they feature high non-stoichiometric oxygen exchange capacities and diffusion rates while maintaining their crystallographic structure during cycling over a wide range of operating conditions and reduction extents. This paper provides an overview of the best performing perovskite formulations considered in recent studies, with special focus on their non-stoichiometry extent, their ability to produce solar fuel with high yield and performance stability, and the different methods developed to study the reaction kinetics.

scholarly journals Selenium– and tellurium–halogen reagents

2018 ◽  
Vol 3 (12) ◽  
Author(s):  
Tristram Chivers ◽  
Risto S. Laitinen
Keyword(s):  
Oxidation State ◽  
Halogen Bond ◽  
The Other ◽  
Oxidation States ◽  
Alkyl Aryl ◽  
Organic Selenium ◽  
Formal Oxidation State ◽  
Wide Range ◽  
Inorganic And Organic

Abstract Selenium and tellurium form binary halides in which the chalcogen can be in formal oxidation states (IV), (II) or (I). They are versatile reagents for the preparation of a wide range of inorganic and organic selenium and tellurium compounds taking advantage of the reactivity of the chalcogen–halogen bond. With the exception of the tetrafluorides, the tetrahalides are either commercially available or readily prepared. On the other hand, the low-valent species, EX2 (E = Se, Te; X = Cl, Br) and E2X2 (E = Se, Te; X = Cl, Br) are unstable with respect to disproportionation and must be used as in situ reagents. Organoselenium and tellurium halides are well-known in oxidation states (IV) and (II), as exemplified by REX3, R2EX2 and REX (R = alkyl, aryl; E = Se, Te; X = F, Cl, Br, I); mixed-valent (IV/II) compounds of the type RTeX2TeR are also known. This chapter surveys the availability and/or preparative methods for these widely used reagents followed by examples of their applications in synthetic inorganic and organic selenium and tellurium chemistry. For both the binary halides and their organic derivatives, the discussion is subdivided according to the formal oxidation state of the chalcogen.

Influence of Chromium Ions on the Dielectric Properties of the PbO-Ga2O3-P2O5 Glass System

2007 ◽  
Vol 62 (5-6) ◽  
pp. 315-323 ◽  
Author(s):  
Gnanaprakasm Little Flower ◽  
Maddireddy Srinivasa Reddy ◽  
Musugu Venkata Ramana Reddy ◽  
Nalluri Veeraiah
Keyword(s):  
Thermal Analysis ◽  
Differential Thermal Analysis ◽  
Dielectric Properties ◽  
Dielectric Breakdown ◽  
Breakdown Strength ◽  
Oxidation States ◽  
Optical Absorption Spectra ◽  
Dielectric Breakdown Strength ◽  
Chromium Ions ◽  
Wide Range

PbO-Ga2O3-P2O5 glasses containing different amounts of Cr2O3, ranging from 0 to 1.0 mol%, were prepared. The dielectric properties (viz., constant ε’, loss tanδ , ac conductivity σac over a wide range of frequencies and temperatures, dielectric breakdown strength) have been studied as a function of the concentration of chromium ions. An anomaly has been observed in the dielectric properties of these glasses, when the concentration of Cr2O3 is about 0.4 mol%. This anomaly has been explained in the light of different oxidation states of chromium ions with the aid of data of differential thermal analysis and optical absorption spectra of these glasses.

Electrochemistry of Redox Active Centres Encapsulated by Non-Covalent Methods

2010 ◽  
Vol 63 (2) ◽  
pp. 184 ◽  
Author(s):  
Suresh Gadde ◽  
Elizabeth K. Batchelor ◽  
Angel E. Kaifer
Keyword(s):  
Electron Transfer ◽  
Direct Electron Transfer ◽  
Electrochemical Behaviour ◽  
Research Work ◽  
Transfer Reactions ◽  
Molecular Receptors ◽  
General Terms ◽  
Redox Active ◽  
Wide Range ◽  
Active Centres

This manuscript presents a summary of recent research work on the electrochemical behaviour of redox active guests fully or almost fully encapsulated by suitable molecular receptors or molecular capsules. From the standpoint of their voltammetric behaviour the cyclodextrins have been shown to be very dynamic hosts, which hamper the observation of direct electron transfer to/from their inclusion complexes. Therefore, this Review is essentially concerned with research work on cucurbituril and cavitand-type hosts, which was mostly done in the author’s laboratory. In general terms, the observed voltammetric behaviour for encapsulated guests covers a wide range of possibilities. Cucurbituril and cavitand-type hosts afford more kinetically stable complexes, whose direct electrochemical behaviour is observable and tends to be kinetically slower than that of the free guests. However, the degree of kinetic attenuation varies over a wide range and, in some cases, challenges our ability to rationalize the data. Clearly, more variation in the host structures and more research work are required to improve our understanding of encapsulation effects on these electron transfer reactions.

scholarly journals Sulfur and Sulfur Compounds in Plant Defence

2012 ◽  
Vol 7 (3) ◽  
pp. 1934578X1200700 ◽  
Author(s):  
Ifeanyi D. Nwachukwu ◽  
Alan J. Slusarenko ◽  
Martin C. H. Gruhlke
Keyword(s):  
Natural Products ◽  
New Technologies ◽  
Plant Defence ◽  
Sulfur Compounds ◽  
Oxidation States ◽  
Chemical Structures ◽  
Wide Range ◽  
Sulfur Containing ◽  
Sulfur Containing Compounds

The multiplicity of chemical structures of sulfur containing compounds, influenced in part by the element's several oxidation states, directly results in diverse modes of action for sulfur-containing natural products synthesized as secondary metabolites in plants. Sulfur-containing natural products constitute a formidable wall of defence against a wide range of pathogens and pests. Steady progress in the development of new technologies have advanced research in this area, helping to uncover the role of such important plant defence molecules like endogenously-released elemental sulphur, but also deepening current understanding of other better-studied compounds like the glucosinolates. As studies continue in this area, it is becoming increasingly evident that sulfur and sulfur compounds play far more important roles in plant defence than perhaps previously suspected.

scholarly journals The Physiological Implications of S-Nitrosoglutathione Reductase (GSNOR) Activity Mediating NO Signalling in Plant Root Structures

Antioxidants ◽  
2020 ◽  
Vol 9 (12) ◽  
pp. 1206
Author(s):  
Leslie Ventimiglia ◽  
Bulent Mutus
Keyword(s):  
Plant Root ◽  
Post Translational Modification ◽  
No Donor ◽  
Stunted Growth ◽  
Cellular Environment ◽  
Redox Active ◽  
Irreversible Reduction ◽  
Wide Range ◽  
Response To Stress ◽  
Cysteine Thiols

Nitrogen remains an important macronutrient in plant root growth due to its application in amino acid production, in addition to its more elusive role in cellular signalling through nitric oxide (NO). NO is widely accepted as an important signalling oxidative radical across all organisms, leading to its study in a wide range of biological pathways. Along with its more stable NO donor, S-nitrosoglutathione (GSNO), formed by NO non-enzymatically in the presence of glutathione (GSH), NO is a redox-active molecule capable of mediating target protein cysteine thiols through the post translational modification, S-nitrosation. S-nitrosoglutathione reductase (GSNOR) thereby acts as a mediator to pathways regulated by NO due to its activity in the irreversible reduction of GSNO to oxidized glutathione (GSSG) and ammonia. GSNOR is thought to be pleiotropic and often acts by mediating the cellular environment in response to stress conditions. Under optimal conditions its activity leads to growth by transcriptional upregulation of the nitrate transporter, NRT2.1, and through its interaction with phytohormones like auxin and strigolactones associated with root development. However, in response to highly nitrosative and oxidative conditions its activity is often downregulated, possibly through an S-nitrosation site on GSNOR at cys271, Though GSNOR knockout mutated plants often display a stunted growth phenotype in all structures, they also tend to exhibit a pre-induced protective effect against oxidative stressors, as well as an improved immune response associated with NO accumulation in roots.

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