Germanium-centered free radicals studied by muon spin spectroscopy

2014 ◽  
Vol 92 (6) ◽  
pp. 508-513 ◽  
Author(s):  
Robert West ◽  
Kerim Samedov ◽  
Amitabha Mitra ◽  
Paul W. Percival ◽  
Jean-Claude Brodovitch ◽  
...  
Keyword(s):  
Free Radicals ◽  
Density Functional ◽  
Muon Spin ◽  
Coupling Reaction ◽  
Transverse Field ◽  
Coupling Constants ◽  
Muon Spin Rotation ◽  
Functional Theory ◽  
Hyperfine Constant ◽  
Germanium Compounds

Transverse-field muon spin rotation (TF-μSR) spectra have been recorded for free radicals formed by positive muon irradiation of nine different divalent germanium compounds. Muon-electron hyperfine coupling constants (Aμ) were determined from the spectra and compared with values predicted from density functional theory molecular orbital (DFT-MO) calculations on the muoniated radicals formed by muonium addition to the germanium atom. The muon hyperfine constants for germylenes containing N–Ge bonds are generally quite large, from 593 to 942 MHz, indicating strong interaction between the muon and the unpaired electron in these radicals. The radical derived from one of the germylenes exhibited a significantly lower muon hyperfine constant, suggesting that in this case the muoniated germyl radical undergoes a coupling reaction to form a digermanyl radical, which is what is detected by μSR.

Radical addition to ruthenocene at low temperatures: characterization of ruthenocenyl radicals by μSR spectroscopy

2018 ◽  
Vol 96 (3) ◽  
pp. 358-362 ◽  
Author(s):  
Iain McKenzie
Keyword(s):  
Dft Calculations ◽  
Spin Relaxation ◽  
Muon Spin ◽  
Transverse Field ◽  
Relaxation Mechanism ◽  
Coupling Constants ◽  
Muon Spin Rotation ◽  
Electron Spin Relaxation ◽  
Spin Resonance ◽  
Experimental Values

The radicals formed by muonium (Mu) addition to ruthenocene at low temperature (4–200 K) have been characterized by transverse field muon spin rotation (TF-μSR) and avoided level crossing muon spin resonance (ALC-μSR) spectroscopy. The structures of the muoniated radicals have been identified by comparing the experimentally measured muon hyperfine coupling constants with values obtained from DFT calculations (UB3LYP/DGDZVP). Mu addition was observed at the ruthenium and at the cyclopentadiene (Cp) rings, both from the exterior and interior directions. Closer agreement between the DFT calculations and the experimental values are obtained if it is assumed the structures of the Mu adducts of the Cp rings are distorted due to interactions with neighbouring molecules. Changes in the ALC-μSR spectra with temperature indicated that the electron spin relaxation rate of the Cp adducts increases with temperature; however, the specific spin relaxation mechanism is unknown.

scholarly journals Superconductivity of Bi-III phase of elemental bismuth: Insights from muon-spin rotation and density functional theory

2018 ◽  
Vol 98 (14) ◽  
Author(s):  
Rustem Khasanov ◽  
Hubertus Luetkens ◽  
Elvezio Morenzoni ◽  
Gediminas Simutis ◽  
Stephan Schönecker ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Muon Spin ◽  
Spin Rotation ◽  
Muon Spin Rotation ◽  
Functional Theory

Radiolabelling Measurements of Radicals Derived from Terpenoid Volatile Organic Conpounds (VOCs) Adsorbed in Porous Carbon

2006 ◽  
Vol 31 (3) ◽  
pp. 159-188 ◽  
Author(s):  
Christopher J. Rhodes
Keyword(s):  
Free Radicals ◽  
Porous Carbon ◽  
Muon Spin ◽  
Activation Parameters ◽  
Transverse Field ◽  
Spin Rotation ◽  
Muon Spin Rotation ◽  
Longitudinal Field ◽  
Reorientational Motion ◽  
Volatile Organic

Radiolabelled free radicals were formed by the addition of muonium-a radioactive hydrogen atom with a positive muon as its nucleus-to α-pinene, β-pinene, dihydrocarvone, dihydrocarveol and dipentene, each as adsorbed in porous carbon. The radicals were identified using transverse-field muon spin rotation (TF-MuSR) and the activation parameters associated with their reorientational motion were measured using longitudinal-field muon spin relaxation (LF-MuSRx). Two distinct adsorbed fractions were detected in each sample, characterised by activation energies in the range 2-6 kJ/mol and 12-16 J/mol respectively.

Assessing the Calculation of Exchange Coupling Constants and Spin Crossover Gaps Using the Approximate Projection Model to Improve Density Function Calculations

2019 ◽  
Author(s):  
Xianghai Sheng ◽  
Lee Thompson ◽  
Hrant Hratchian
Keyword(s):  
Density Functional Theory ◽  
Exchange Coupling ◽  
Density Functional ◽  
Spin Crossover ◽  
Coupling Constants ◽  
Spin Projection ◽  
Coupling Constant ◽  
Projection Model ◽  
Functional Theory

This work evaluates the quality of exchange coupling constant and spin crossover gap calculations using density functional theory corrected by the Approximate Projection model. Results show that improvements using the Approximate Projection model range from modest to significant. This study demonstrates that, at least for the class of systems examined here, spin-projection generally improves the quality of density functional theory calculations of J-coupling constants and spin crossover gaps. Furthermore, it is shown that spin-projection can be important for both geometry optimization and energy evaluations. The Approximate Project model provides an affordable and practical approach for effectively correcting spin-contamination errors in molecular exchange coupling constant and spin crossover gap calculations.

Hexaethyl-2,4-dicarba-nido-hexaborane(8), Deprotonation and Complexation Studied by NMR Spectroscopy and Density Functional Theory (DFT) Calculations

2004 ◽  
Vol 59 (6) ◽  
pp. 685-691 ◽  
Author(s):  
Bernd Wrackmeyer ◽  
Hans-Jörg Schanz
Keyword(s):  
Density Functional Theory ◽  
Nmr Spectroscopy ◽  
Density Functional ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Analogous Reaction ◽  
Sandwich Complex ◽  
Dft Methods ◽  
Functional Theory ◽  
Nmr Data

Deprotonation of hexaethyl-2,4-dicarba-nido-borane(8) 2 leads first to the hexaethyl-2,4-dicarbanido- borate(1−) 3, and further deprotonation, using BuLi/KOtBu, gives the hexaethyl-2,4-dicarbanido- hexaborate(2−) 4. The reaction of 3 with FeCl2 affords the commo-ferracarborane [Fe(Et6-2,4- C2B4H)2] 5, and the analogous reaction of 4 leads to the anionic sandwich complex [Fe(Et6-2,4- C2B4)2]2− 6 which can be protonated to give 5. The complex 5 contains two hydrido ligands, each bridging the iron and two boron atoms. Reactions were monitored and the products were characterised by 11B NMR spectroscopy in solution. The geometries of the carboranes, the borates (all unsubstituted and permethyl-substituted) and the iron complexes (all unsubstituted) were optimised by DFT methods [B3LYP/6-311+G(d,p) or B3LYP/6-31+G(d)], and the relevant NMR data [chemical shifts δ11B, δ13C, δ57Fe, and coupling constants 1J(13C,1H), 1J(11B,1H), 1J(57Fe,1H), 1J(57Fe,11B)] were calculated at the same level of theory.

Intramolecular Motion in Organic free Radicals Studied by Muon Spin Rotation and Level-Crossing Spectroscopy

1988 ◽  
pp. 155-156
Author(s):  
P. W. Percival ◽  
J. -C. Brodovitch ◽  
S. -K. Leung ◽  
D. Yu ◽  
R. F. Kiefl ◽  
...  
Keyword(s):  
Free Radicals ◽  
Muon Spin ◽  
Spin Rotation ◽  
Muon Spin Rotation ◽  
Level Crossing ◽  
Intramolecular Motion

scholarly journals A novel selective fluorescent chemosensor for Fe3+ ions based on phthalonitrile dimer: synthesis, analysis, and theoretical studies

2020 ◽  
Vol 44 (5) ◽  
pp. 1254-1264
Author(s):  
Shaya AL-RAQA ◽  
İpek ÖMEROĞLU ◽  
Doğan ERBAHAR ◽  
Mahmut DURMUŞ
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Interaction Mechanism ◽  
Coupling Reaction ◽  
Cross Coupling ◽  
Density Functional Theory Calculations ◽  
Theoretical Studies ◽  
Functional Theory ◽  
Cross Coupling Reaction ◽  
Ft Ir

Phenyl-4,4-di(3,6-dibutoxyphthalonitrile) (3) was synthesized by the reaction of 1,4-phenylenebisboronic acid (1) and 4-bromo-3,6-dibutoxyphthalonitrile (2), using Suzuki cross-coupling reaction. The newly synthesized compound (3) was characterized by FT-IR, MALDI-MS, ESI-MS, 1H-NMR, 13C-NMR, and 13C-DEPT-135-NMR. The fluorescence property of phenyl-4,4-di(3,6- dibutoxyphthalonitrile) (3) towards various metal ions was investigated by fluorescence spectroscopy, and it was observed thatthe compound (3) displayed a significantly ‘turn-off’ response to Fe3+, which was referred to 1:2 complex formation between ligand (3) and Fe3+. The compound was also studied via density functional theory calculations revealing the interaction mechanism of the molecule with Fe3+ ions.

Theory of Nuclear Quadrupole Interactions of 14N, 17O, and 35Cl Nuclei in p-Cl-Ph-CH-N=TEMPO

2002 ◽  
Vol 57 (6-7) ◽  
pp. 527-531
Author(s):  
Junho Jeong ◽  
Tina M. Briere ◽  
N. Sahoo ◽  
T. P. Das ◽  
S. Ohira ◽  
...  
Keyword(s):  
Muon Spin ◽  
Hyperfine Interactions ◽  
Rotation Frequency ◽  
Coupling Constants ◽  
Muon Spin Rotation ◽  
Hartree Fock ◽  
Nuclear Quadrupole Interactions ◽  
Quadrupole Coupling ◽  
Nuclear Quadrupole ◽  
Asymmetry Parameters

The nuclear quadrupole coupling constants and asymmetry parameters have been studied for the 35Cl, 17O, and 14N nuclei in the molecular ferromagnet 4-(p-chlorobenzylideneamino)-TEMPO (2,2,6,6-tetramethyl- piperidin-1-yloxyl) using elctronic stuctures obtained by the Hartree-Fock procedure for the bare system and systems with trapped muon and muonium. Trends in the sizes of the coupling constants and asymmetry parameters for the various nuclei have been studied, and possible physical explanations have been proposed. For the systems with trapped muon or muonium, very substantial influences of the muon and muonium on the coupling constants and asymmetry parameters for the nuclei close to the trapping sites have been observed. The coupling constants and asymmetry parameters are found to be very different for the various nuclei, for the two cases where muon is trapped near chlorine and muonium near oxygen, indicating that, if experimental data were available to compare with theory, one could make conclusions about which of these two centers is responsible for the observed muon spin rotation frequency associated with the muon magnetic hyperfine interactions in these two trapped systems

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