scholarly journals Intramolecular Mobility in Nitroxide Biradicals with Flexible Linkers

2020 ◽  
Vol 51 (9-10) ◽  
pp. 1031-1040
Author(s):  
Günter Grampp ◽  
Van Anh Tran ◽  
Petr V. Pantyukhov ◽  
Alexander I. Kokorin
Keyword(s):  
Thermodynamic Parameters ◽  
Spin Exchange ◽  
Thermodynamic Characteristics ◽  
Conformational Transitions ◽  
Polar Solvents ◽  
Paramagnetic Resonance ◽  
Solvent Viscosity ◽  
X Band ◽  
Intramolecular Mobility ◽  
Electron Paramagnetic

Abstract Intramolecular electron spin exchange has been studied by X-band electron paramagnetic resonance (EPR) spectroscopy in two long-chain flexible nitroxide biradicals existing in fluid solutions in three spectroscopy-different spatial conformations as a function of temperature, solvent viscosity and polarity. Certain thermodynamic parameters of the conformational transitions were calculated from the EPR spectra. The process of spin-exchange in these biradicals dissolved in five different alcohols was compared with that in the non-polar solvents (toluene) and aprotic (acetonitrile), as well as with two other biradicals studied earlier, and with thermodynamic characteristics of the solvents. A distinct correlation was found between macroscopic (solvent viscosity) characteristics of solvents and thermodynamic parameters of the intramolecular conformational transitions.

scholarly journals Photoreactivity of Hair Melanin from Different Skin Phototypes—Contribution of Melanin Subunits to the Pigments Photoreactive Properties

2021 ◽  
Vol 22 (9) ◽  
pp. 4465
Author(s):  
Krystian Mokrzynski ◽  
Shosuke Ito ◽  
Kazumasa Wakamatsu ◽  
Theodore G. Camenish ◽  
Tadeusz Sarna ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Singlet Oxygen ◽  
Near Infrared ◽  
Paramagnetic Resonance ◽  
Time Resolved ◽  
W Band ◽  
Epr Oximetry ◽  
X Band ◽  
Hair Samples ◽  
Electron Paramagnetic

Photoreactivity of melanin has become a major focus of research due to the postulated involvement of the pigment in UVA-induced melanoma. However, most of the hitherto studies were carried out using synthetic melanin models. Thus, photoreactivity of natural melanins is yet to be systematically analyzed. Here, we examined the photoreactive properties of natural melanins isolated from hair samples obtained from donors of different skin phototypes (I, II, III, and V). X-band and W-band electron paramagnetic resonance (EPR) spectroscopy was used to examine the paramagnetic properties of the pigments. Alkaline hydrogen peroxide degradation and hydroiodic acid hydrolysis were used to determine the chemical composition of the melanins. EPR oximetry and spin trapping were used to examine the oxygen photoconsumption and photo-induced formation of superoxide anion, and time-resolved near infrared phosphorescence was employed to determine the singlet oxygen photogeneration by the melanins. The efficiency of superoxide and singlet oxygen photogeneration was related to the chemical composition of the studied melanins. Melanins from blond and chestnut hair (phototypes II and III) exhibited highest photoreactivity of all examined pigments. Moreover, melanins of these phototypes showed highest quantum efficiency of singlet oxygen photogeneration at 332 nm and 365 nm supporting the postulate of the pigment contribution in UVA-induced melanoma.

An X-band time domain electron paramagnetic resonance spectrometer

Pramana ◽  
1986 ◽  
Vol 27 (5) ◽  
pp. 661-677 ◽  
Author(s):  
Ranjan Das ◽  
Balu Venkataraman ◽  
Vinod R Bhagat ◽  
Ajit S Ghangrekar ◽  
Thomas Kuruvilla ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Time Domain ◽  
Electron Paramagnetic Resonance Spectrometer ◽  
Paramagnetic Resonance ◽  
X Band ◽  
Electron Paramagnetic

X-band electron paramagnetic resonance of a quasi-bidimensional molecular composite [NH3(CH2)4NH3]CuCl4

1996 ◽  
Vol 97 (8) ◽  
pp. 669-674 ◽  
Author(s):  
Jean-Claude Bissey ◽  
René Berger ◽  
Pierre Béziade ◽  
Nguyen-Ba Chanh ◽  
Thierry Maris ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Paramagnetic Resonance ◽  
Band Electron ◽  
X Band ◽  
Electron Paramagnetic

scholarly journals Comparison of Continuous Wave and Rapid Scan X-band Electron Paramagnetic Resonance of Irradiated Clipped Fingernails

2016 ◽  
Vol 172 (1-3) ◽  
pp. 133-138 ◽  
Author(s):  
Hanan Elajaili ◽  
Joseph McPeak ◽  
Alexander Romanyukha ◽  
Priyanka Aggarwal ◽  
Sandra S. Eaton ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Continuous Wave ◽  
Paramagnetic Resonance ◽  
Band Electron ◽  
Rapid Scan ◽  
X Band ◽  
Electron Paramagnetic

Eu2+-Containing Luminescent Perovskite-Type Hydrides Studied by Electron Paramagnetic Resonance

2016 ◽  
Vol 230 (5-7) ◽  
Author(s):  
Nathalie Kunkel ◽  
Rolf Böttcher ◽  
Tilo Pilling ◽  
Holger Kohlmann ◽  
Andreas Pöppl
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Lattice Site ◽  
Metal Hydrides ◽  
Ligand Field ◽  
Site Symmetry ◽  
Paramagnetic Resonance ◽  
Band Electron ◽  
X Band ◽  
Electron Paramagnetic ◽  
Perovskite Type

AbstractMetal hydrides exhibit interesting properties as hosts for Eu(II) containing luminescent compounds due to the nephelauxetic effect and the strong ligand field of the hydride anion. In order to elucidate the lattice site symmetry of europium dopants, Q-band and X-band electron paramagnetic resonance (EPR) spectra were collected on LiMH

Nitrogen Centers in Nanodiamonds: EPR Studies

2010 ◽  
Vol 645-648 ◽  
pp. 1239-1242 ◽  
Author(s):  
Alexandra A. Soltamova ◽  
P.G. Baranov ◽  
Ivan V. Ilyin ◽  
A.Y. Vul' ◽  
S.V. Kidalov ◽  
...  
Keyword(s):  
Spin Echo ◽  
Natural Diamond ◽  
Electron Spin Echo ◽  
Atomic Nitrogen ◽  
Paramagnetic Resonance ◽  
W Band ◽  
High Pressure High Temperature ◽  
X Band ◽  
Epr Signal ◽  
Electron Paramagnetic

Electron paramagnetic resonance (EPR) and electron spin echo (ESE) at X-band (9.4 GHz) and W-band (94 GHz) have been used to study defects in natural diamond nanocrystals, detonation nanodiamond (ND) with a size of  4.5 nm and detonation ND after high-pressure high-temperature (HTHP) sintering with a size of  8.5 nm. Based on identification of atomic nitrogen centers N0 and nitrogen pairs N2+ detected by means of the high frequency EPR and ESE in natural diamond nanocrystals, atomic nitrogen centers N0 have been discovered in nanodiamond core in detonation ND and detonation ND after sintering. In addition EPR signal of multi-vacancy centers with spin 3/2 seems to be observed in diamond core of detonation ND.

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