Resolving the Unpaired‐Electron Orbital Distribution in a Stable Organic Radical by Kondo Resonance Mapping

2019 ◽  
Vol 58 (32) ◽  
pp. 11063-11067 ◽  
Author(s):  
Laerte L. Patera ◽  
Sophia Sokolov ◽  
Jonathan Z. Low ◽  
Luis M. Campos ◽  
Latha Venkataraman ◽  
...  
Keyword(s):  
Unpaired Electron ◽  
Organic Radical ◽  
Kondo Resonance ◽  
Electron Orbital

First Observation of a Kondo Resonance for a Stable Neutral Pure Organic Radical, 1,3,5-Triphenyl-6-oxoverdazyl, Adsorbed on the Au(111) Surface

2012 ◽  
Vol 135 (2) ◽  
pp. 651-658 ◽  
Author(s):  
Jie Liu ◽  
Hironari Isshiki ◽  
Keiichi Katoh ◽  
Takaumi Morita ◽  
Brian, K. Breedlove ◽  
...  
Keyword(s):  
Organic Radical ◽  
Kondo Resonance

Nature of the Unpaired Electron Orbital in Some Low Spin Oxygen-Co Complexes

1968 ◽  
Vol 1 (1) ◽  
pp. 49-54 ◽  
Author(s):  
Hideo Kon ◽  
Norman E. Sharpless
Keyword(s):  
Unpaired Electron ◽  
Electron Orbital

Field-Ion Microscopy of BCC Metals: A Study of Image Differences and Topographical Variations

1973 ◽  
Vol 31 ◽  
pp. 114-115
Author(s):  
O. T. Inal ◽  
L. E. Murr
Keyword(s):  
Liquid Nitrogen ◽  
Liquid Nitrogen Temperature ◽  
Surface Atom ◽  
Image Brightness ◽  
Field Ion Microscopy ◽  
Topographic Features ◽  
Bcc Metals ◽  
Electron Orbital ◽  
Ion Microscopy ◽  
Field Ion Microscope

When sharp metal filaments of W, Fe, Nb or Ta are observed in the field-ion microscope (FIM), their appearance is differentiated primarily by variations in regional brightness. This regional brightness, particularly prominent at liquid nitrogen temperature has been attributed in the main to chemical specificity which manifests itself in a paricular array of surface-atom electron-orbital configurations.Recently, anomalous image brightness and streaks in both fcc and bee materials observed in the FIM have been shown to be the result of surface asperities and related topographic features which arise by the unsystematic etching of the emission-tip end forms.

Development of new magnetic organic conductors based on donor molecules with stable organic radical part

2004 ◽  
Vol 114 ◽  
pp. 533-535 ◽  
Author(s):  
H.-J. Lee ◽  
H.-B. Cui ◽  
H. Fujiwara ◽  
H. Kobayashi ◽  
E. Fujiwara ◽  
...  
Keyword(s):  
Organic Conductors ◽  
Organic Radical

Nitroxyl Modified Tobacco Mosaic Virus as a Metal-Free High-Relaxivity MRI and EPR Active Superoxide Sensor

2018 ◽  
Author(s):  
Madushani Dharmarwardana ◽  
André F. Martins ◽  
Zhuo Chen ◽  
Philip M. Palacios ◽  
Chance M. Nowak ◽  
...  
Keyword(s):  
Tobacco Mosaic Virus ◽  
Mosaic Virus ◽  
Single Molecule ◽  
Biological Fluids ◽  
Cellular Respiration ◽  
Organic Radical ◽  
Paramagnetic Resonance ◽  
Metal Free ◽  
Disease States

Superoxide overproduction is known to occur in multiple disease states requiring critical care yet non-invasive detection of superoxide in deep tissue remains a challenge. Herein, we report a metal-free magnetic resonance imaging (MRI) and electron paramagnetic resonance (EPR) active contrast agent prepared by “click conjugating” paramagnetic organic radical contrast agents (ORCAs) to the surface of tobacco mosaic virus (TMV). While ORCAs are known to be reduced <i>in vivo</i> to an MRI/EPR silent state, their oxidation is facilitated specifically by reactive oxygen species—in particular superoxide—and are largely unaffected by peroxides and molecular oxygen. Unfortunately, single molecule ORCAs typically offer weak MRI contrast. In contrast, our data confirm that the macromolecular ORCA-TMV conjugates show marked enhancement for <i>T<sub>1</sub></i> contrast at low field (<3.0 T), and <i>T<sub>2</sub></i> contrast at high field (9.4 T). Additionally, we demonstrated that the unique topology of TMV allows for “quenchless fluorescent” bimodal probe for concurrent fluorescence and MRI/EPR imaging, which was made possible by exploiting the unique inner and outer surface of the TMV nanoparticle. <a>Finally, we show TMV-ORCAs do not respond to normal cellular respiration, minimizing the likelihood for background, yet still respond to enzymatically produced superoxide in complicated biological fluids like serum.</a>

Supramolecular Enhancement of Aminoxyl ORCA Contrast Agents

2019 ◽  
Author(s):  
Hamilton Lee ◽  
Jenica Lumata ◽  
Michael A. Luzuriaga ◽  
Candace Benjamin ◽  
Olivia Brohlin ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Side Effects ◽  
Magnetic Resonance ◽  
Tobacco Mosaic Virus ◽  
Contrast Agents ◽  
Single Molecule ◽  
Organic Radical ◽  
Resonance Imaging ◽  
Physiological Conditions

<div><div><div><p>Many contrast agents for magnetic resonance imaging are based on gadolinium, however side effects limit their use in some patients. Organic radical contrast agents (ORCAs) are potential alternatives, but are reduced rapidly in physiological conditions and have low relaxivities as single molecule contrast agents. Herein, we use a supramolecular strategy where cucurbit[8]uril binds with nanomolar affinities to ORCAs and protects them against biological reductants to create a stable radical in vivo. We further over came the weak contrast by conjugating this complex on the surface of a self-assembled biomacromolecule derived from the tobacco mosaic virus.</p></div></div></div>

Alkyl 1-[2-(oxido anion)-, 3-, 4-, 5-alkyl substituted]phenyl ketyl radicals

1979 ◽  
Vol 44 (6) ◽  
pp. 1731-1741 ◽  
Author(s):  
Andrej Staško ◽  
Ľubomír Malík ◽  
Alexander Tkáč ◽  
Vladimír Adamčík ◽  
Eva Maťašová
Keyword(s):  
Electron Donor ◽  
Unpaired Electron ◽  
Grignard Reagents ◽  
Slight Effect ◽  
Benzene Nucleus ◽  
Alkyl Groups ◽  
Splitting Constant

Reactions of R2,R3-alkyl substituted 2-hydroxybenzenecarboxylic acids 2-HO-C6H2R2-COOH with Grignard reagents R1MgBr in the presence of nickel give stable aryl alkyl ketyl radicals 2-O--R2-, R3-C6H2-CO--R1 where R1 = CH3, C2H5, C2D5, n-C3H7 and R2,R3 = CH3, C2H5, i-C3H7, t-C4H9. The β protons of ketyl group are equivalent (splitting constant 1.25 mT) and non-equivalent (splitting constants within 0.5 to 1.5 mT) for R1 = methyl and other alkyl groups, respectively. Interaction of the γ protons with the unpaired electron was only observed in the case of R1 = n-propyl (splitting constants about 0.07 mT). The substituents R1 have but slight effect on values of splitting constants of the protons in R2,R3 and vice versa. Also splitting constants of the benzene nucleus (a4H = 0.55 mT, a6H = 0.44 mT) are only slightly affected by the substituents R1,R2,R3, which indicates dominant electron-donor effect of the oxido-anion group eliminating the relatively smaller contributions of the alkyl substituents.

ESR study of the structure and bonding situation in thiocyanatocopper(II) complexes with imidazole derivatives

1988 ◽  
Vol 53 (1) ◽  
pp. 56-60
Author(s):  
Anna Mašlejová ◽  
Reinhard Kirmse
Keyword(s):  
Unpaired Electron ◽  
Hyperfine Splitting ◽  
Esr Spectra ◽  
Ligand Field ◽  
Imidazole Derivatives ◽  
Bonding Parameters ◽  
Monomeric Complex ◽  
Structure And Bonding ◽  
Frozen Solutions ◽  
Planar Symmetry

ESR spectra of thianatocopper(II) complexes with imidazole derivatives were studied in ethanolic solutions at 295 and 123 K. Axialsymmetric spectra, attributed to the monomeric complex units, were obtained for the frozen solutions. The bonding parameters were interpreted by using calculated g, Cu-hyperfine, and 14N-ligand hyperfine splitting values. The Cu-N bond parameters indicate a considerable delocalization of the unpaired electron. The values of the isotropic Cu-hyperfine splitting suggest that the deviations from the planar symmetry of the CuN4 units are due to tetrahedral perturbation of the ligand field.

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