An electron spin resonance and CIDNP study of the structure and reactivity of some excited triplet biphenyl ketones

1977 ◽  
Vol 55 (7) ◽  
pp. 1175-1180 ◽  
Author(s):  
Harish M. Vyas ◽  
Jeffrey K. S. Wan
Keyword(s):  
Electron Spin Resonance ◽  
Low Temperature ◽  
Light Intensity ◽  
Oxygen Atom ◽  
Carbonyl Oxygen ◽  
Zero Field ◽  
Carbonyl Groups ◽  
Excited Triplet ◽  
Spin Resonance ◽  
Unpaired Spin

The correlation of structure and reactivity of some excited triplet biphenyl ketones was approached by a combined esr and CIDNP study. The low temperature esr study confirmed the assignment of the triplet π,π* as the lowest triplet state in these biphenyl ketones. An analysis of the zero-field energies suggests that these π,π* triplets have a structure with both the biphenyl and the carbonyl groups being coplanar. Consequently a substantial unpaired spin density may result at the carbonyl oxygen atom which could lead to abstraction reactions. The CIDNP results are consistent with the triplet photoreduction mechanism. The polarization is mainly due to the cage products and the polarization magnitude is therefore dependent upon the light intensity

Applications of ESR to Carbonaceous Materials

1982 ◽  
Vol 36 (1) ◽  
pp. 52-57 ◽  
Author(s):  
L. S. Singer ◽  
I. C. Lewis
Keyword(s):  
Free Radicals ◽  
Electron Spin Resonance ◽  
Low Temperature ◽  
Electron Spin ◽  
Paramagnetic Species ◽  
Carbonaceous Materials ◽  
Conduction Electrons ◽  
Spin Resonance ◽  
Higher Temperature ◽  
Low Temperature Pyrolysis

The applications of electron spin resonance (ESR) to carbonaceous materials are reviewed. The stable paramagnetic species observed in the products of low-temperature pyrolysis are odd-alternate neutral free radicals, whereas the unpaired spins of higher temperature carbons and graphites are primarily conduction electrons. The variety of ESR properties and phenomena requires special attention to techniques of measurement and interpretations of results. The relevance to the carbonization process of the free radicals observed by ESR is also discussed.

Paramagnetic resonance and optical absorption of trapped holes and electrons in irradiated KCI: Ag

1963 ◽  
Vol 271 (1345) ◽  
pp. 243-267 ◽  
Keyword(s):  
Electron Spin Resonance ◽  
Low Temperature ◽  
Optical Absorption ◽  
Electron Spin ◽  
Optical Absorption Spectra ◽  
Paramagnetic Resonance ◽  
Spin Resonance ◽  
Impurity Ions ◽  
Temperature Irradiation ◽  
Positive Holes

The electron spin resonance and optical absorption spectra of crystals of KCl containing silver impurity ions were examined after the crystals had been X -irradiated at 77 °K. It is shown that the silver impurity ions act as traps for both electrons and positive holes. A description is given of the annealing behaviour of the crystals after low-temperature irradiation.

scholarly journals The Coordination Chemistry of Phosphoryl Compounds Containing the -N(CH3)2 Group, XII.

1973 ◽  
Vol 28 (3-4) ◽  
pp. 104-106 ◽  
Author(s):  
M.W.G. De Bolster ◽  
B. Nieuwenhuijse ◽  
J. Reedijk
Keyword(s):  
Electron Spin Resonance ◽  
Metal Ion ◽  
Room Temperature ◽  
Esr Spectroscopy ◽  
Hyperfine Coupling ◽  
Hyperfine Coupling Constant ◽  
Zero Field ◽  
Coupling Constant ◽  
Spin Resonance ◽  
Temperature Electron

Room temperature electron spin resonance powder spectra have been recorded for some compounds of the type Mn(ligand)p(anion)2 with hexamethylphosphoramide and nonamethylimidodiphosphoramide as ligands (p = 1 - 4) and BF-4, NO-3, Cl-, Br-, I- and NCS-as anions.The values for the zero-field parameters, D and λ, have been determined and are compared with literature data. It is shown that ESR spectroscopy can be very helpful in elucidating the structures of manganese(II) complexes.The high values for the hyperfine coupling constant of the solvates suggest that in these complexes the bonding between the ligands and the metal ion is essentially ionic.

Sign in / Sign up

Export Citation Format

Share Document