scholarly journals Remote Oxidative Activation of a [Cp*Rh] Monohydride

2021 ◽  
Author(s):  
Emily Boyd ◽  
Julie Hopkins Leseberg ◽  
Emma Cosner ◽  
Davide Lionetti ◽  
Wade Henke ◽  
...  
Keyword(s):  
Electrochemical Oxidation ◽  
Epr Spectroscopy ◽  
Redox Activity ◽  
Electrochemical Studies ◽  
Attractive Feature ◽  
Nmr Studies ◽  
Reactivity Pattern ◽  
Oxidative Activation ◽  
Half Sandwich

Half-sandwich rhodium monohydrides are often proposed as intermediates in catalysis, but little is known regarding the redox-induced reactivity accessible to these species. Here, the κ2-bis-diphenylphosphinoferrocene (dppf) ligand has been used to explore the reactivity that can be induced when a [Cp*Rh] monohydride undergoes remote (dppf-centered) oxidation by 1e–. Chemical and electrochemical studies showed that one-electron redox chemistry is accessible to Cp*Rh(dppf), including a unique quasi-reversible RhII/I process at –0.96 V vs. ferrocenium/ferrocene (Fc+/0). This redox manifold was confirmed by isolation of an uncommon Rh(II) species that was characterized by EPR spectroscopy. Protonation of Cp*Rh(dppf) with anilinium triflate yielded an isolable and inert monohydride, and this species was found to undergo a quasireversible electrochemical oxidation at +0.41 V vs Fc+/0 that corresponds to iron-centered oxidation in the dppf backbone. Thermochemical analysis predicts that this dppf-centered oxidation drives a dramatic increase in acidity of the Rh–H moiety by 23 pKa units, a reactivity pattern confirmed by in situ 1H NMR studies. Taken together, these results show that remote oxidation can effectively induce M–H activation and suggest that ligand-centered redox activity could be an attractive feature for design of new systems relying on hydride intermediates.

Properties of electrochemically generated primary cationradicals of phenyl- and 2-(4-tolyl)-1,3,4,7-tetramethylisoindoles

1980 ◽  
Vol 45 (6) ◽  
pp. 1669-1676 ◽  
Author(s):  
Pavel Kubáček
Keyword(s):  
Electrochemical Oxidation ◽  
Spin Polarization ◽  
High Spin ◽  
Epr Spectroscopy ◽  
Half Life ◽  
Electrochemical Behaviour ◽  
Epr Spectra ◽  
Electrochemical Generation ◽  
Splitting Constant ◽  
Reduced Temperature

The first step of electrochemical oxidation of 2-phenyl- and 2-(4-tolyl)-1,3,4,7-tetramethylisoindoles in anhydrous acetonitrile produces relatively stable cationradicals which have been studied by means of EPR spectroscopy using the method of internal electrochemical generation of radicals under reduced temperature. The same electrochemical behaviour of the both studied derivatives and identical EPR spectra of their cationradicals can be explained within the Huckel MO method. The largest contribution to the magnitude of splitting constant of nitrogen nucleus is due to π-σ-spin polarization of C-N bonds caused by high spin abundance of pz-AO of carbon atoms. Half-life of decomposition of the studied cationradicals is 4 min at -30°C.

scholarly journals Enzymatic Degradation of Phenazines Can Generate Energy and Protect Sensitive Organisms from Toxicity

mBio ◽  
2015 ◽  
Vol 6 (6) ◽  
Author(s):  
Kyle C. Costa ◽  
Megan Bergkessel ◽  
Scott Saunders ◽  
Jonas Korlach ◽  
Dianne K. Newman
Keyword(s):  
Microbial Communities ◽  
Pathogenic Fungi ◽  
Cell Types ◽  
Redox Activity ◽  
Mycobacterium Fortuitum ◽  
Active Metabolites ◽  
Content Type ◽  
Phenazine Production ◽  
Physiological Benefits

ABSTRACTDiverse bacteria, including severalPseudomonasspecies, produce a class of redox-active metabolites called phenazines that impact different cell types in nature and disease. Phenazines can affect microbial communities in both positive and negative ways, where their presence is correlated with decreased species richness and diversity. However, little is known about how the concentration of phenazines is modulatedin situand what this may mean for the fitness of members of the community. Through culturing of phenazine-degrading mycobacteria, genome sequencing, comparative genomics, and molecular analysis, we identified several conserved genes that are important for the degradation of threePseudomonas-derived phenazines: phenazine-1-carboxylic acid (PCA), phenazine-1-carboxamide (PCN), and pyocyanin (PYO). PCA can be used as the sole carbon source for growth by these organisms. Deletion of several genes inMycobacterium fortuitumabolishes the degradation phenotype, and expression of two genes in a heterologous host confers the ability to degrade PCN and PYO. In cocultures with phenazine producers, phenazine degraders alter the abundance of different phenazine types. Not only does degradation support mycobacterial catabolism, but also it provides protection to bacteria that would otherwise be inhibited by the toxicity of PYO. Collectively, these results serve as a reminder that microbial metabolites can be actively modified and degraded and that these turnover processes must be considered when the fate and impact of such compounds in any environment are being assessed.IMPORTANCEPhenazine production byPseudomonasspp. can shape microbial communities in a variety of environments ranging from the cystic fibrosis lung to the rhizosphere of dryland crops. For example, in the rhizosphere, phenazines can protect plants from infection by pathogenic fungi. The redox activity of phenazines underpins their antibiotic activity, as well as providing pseudomonads with important physiological benefits. Our discovery that soil mycobacteria can catabolize phenazines and thereby protect other organisms against phenazine toxicity suggests that phenazine degradation may influence turnoverin situ. The identification of genes involved in the degradation of phenazines opens the door to monitoring turnover in diverse environments, an essential process to consider when one is attempting to understand or control communities influenced by phenazines.

In Situ Monitoring of Cement Gel Growth Dynamics. Use of a Miniaturized Permanent Halbach Magnet for Precise1H NMR Studies

2010 ◽  
Vol 49 (2) ◽  
pp. 613-622 ◽  
Author(s):  
Eleni Karakosta ◽  
George Diamantopoulos ◽  
Marios S. Katsiotis ◽  
Michael Fardis ◽  
Georgios Papavassiliou ◽  
...  
Keyword(s):  
Growth Dynamics ◽  
In Situ Monitoring ◽  
Gel Growth ◽  
Nmr Studies

A kinetic study of mechanochemical halogen bond formation by in situ31P solid-state NMR spectroscopy

2017 ◽  
Vol 53 (71) ◽  
pp. 9930-9933 ◽  
Author(s):  
Yijue Xu ◽  
Lysiane Champion ◽  
Bulat Gabidullin ◽  
David L. Bryce
Keyword(s):  
Activation Energy ◽  
Solid State ◽  
Nmr Spectroscopy ◽  
Kinetic Study ◽  
Solid State Nmr ◽  
Halogen Bond ◽  
Bond Formation ◽  
Nmr Studies ◽  
Solid State Nmr Spectroscopy

In situ 31P solid-state NMR studies of mechanochemical halogen bond formation provide insights into the cocrystallisation process and an estimate of the activation energy.

In Situ ATR-IR Observation of the Electrochemical Oxidation of a Polycrystalline Boron-Doped Diamond Electrode in Acidic Solutions

2018 ◽  
Vol 122 (48) ◽  
pp. 27456-27461 ◽  
Author(s):  
Taiga Ogose ◽  
Seiji Kasahara ◽  
Norihito Ikemiya ◽  
Nagahiro Hoshi ◽  
Yasuaki Einaga ◽  
...  
Keyword(s):  
Electrochemical Oxidation ◽  
Boron Doped Diamond ◽  
Acidic Solutions ◽  
Diamond Electrode ◽  
Boron Doped ◽  
Boron Doped Diamond Electrode

Voltammetric and in situ FTIRS study of the electrochemical oxidation of aniline from aqueous solutions buffered at pH 5

2001 ◽  
Vol 501 (1-2) ◽  
pp. 186-192 ◽  
Author(s):  
F. Cases ◽  
F. Huerta ◽  
P. Garcés ◽  
E. Morallón ◽  
J.L. Vázquez
Keyword(s):  
Aqueous Solutions ◽  
Electrochemical Oxidation ◽  
In Situ Ftirs
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