Paramagnetic resonance absorption

Bennett, J.E., Ingram, D.J.E., George, P., and Griffith, J.S. 1955. Paramagnetic resonance absorption of ferrihaemoglobin and ferrimyoglobin derivatives. Nature 176 394-394. 

The effects of an uncompensated electron are (1) to split the molecule s spectral lines into doublets, or in the case of certain diradicals, into triplets, (2) to make the molecule paramagnetic, (3) to catalyze the conversion of para and ortho hydrogen molecules, and (4) to cause paramagnetic resonance absorption. 

The method of paramagnetic resonance absorption makes use of the precession of the spinning impaired electron when it is placed in a magnetic field. This precession gives rise to absorption of radiation in the microwave region. The frequency at which the absorption takes place is given by the expression... 

The initial product of the inhibition step is not known in this case and may be a molecular complex.8 The direct reaction of the ethane with the peroxy radical is an example of a covalent compound giving a reaction resembling that of a related free radical. The molecular weight determination by Gomberg was therefore a necessary part of the proof that he was dealing with radicals and not merely an unusually reactive hydrocarbon. The presence of free radicals has since been confirmed by measurements of the paramagnetic susceptibility and the paramagnetic resonance absorption.9-10 The latter evidence also rules out an alter-... 

The primary measure of the amount of free radical must depend on those properties unambiguously due to the unpaired electron. In the past the most common method has been the measurement of the paramagnetic susceptibility, now subject to difficulties of quantitative interpretation. The method of paramagnetic resonance absorption is... 

Hie sodium derivative of triphenylboron gives several radical-like reactions but shows no paramagnetic resonance absorption. It probably exists as the dimer.87... 

A diradical is an atom or molecule containing two impaired electrons. The properties of diradicals are for the most part like those of monoradicals. They are paramagnetic and show paramagnetic resonance absorption. Although they are very reactive chemically, this is not a reliable criterion for the diradical state. Spectroscopically the diradical will probably be a triplet state if a double bond structure coupling the two electrons is geometrically possible. But when the two electrons are fairly well isolated from each other the state is probably a double doublet, like two independent radicals. 

Porphyrindine has been shown to be a diradical both by its paramagnetism and by paramagnetic resonance absorption.72-78... 

A diradical is likely to be more polarizable and a stronger base than the corresponding singlet state. If so, reaction with an acid should shift the equilibrium enough for the diradical to be detectable in otherwise diamagnetic substances. This seems to be the case for the substances shown below, in which paramagnetic resonance absorption indicates the presence of the diradical conjugate acid to the extent... 

A reaction analogous to the formation of metal ketyls is the formation of negative ion-radicals not only from aromatic nitro compounds but also from aromatic hydrocarbons like naphthalene. These substances are highly colored and exhibit paramagnetic resonance absorption.128... 

Thianthrene and diphenyl disulfide show no detectable paramagnetic resonance absorption in inert solvents, but appear to dissociate somewhat in sulfuric acid solution.78... 

Since the discovery of the phenomenon of paramagnetic resonance absorption by Zavoisky 19) in 1945, this method has been extensively applied to the study of the properties of unpaired electrons in various substances. A large amount of information has been obtained concerning the transition group elements in various valence states and is summarized in review articles 20) generally these elements have been studied in dilute concentration in a diamagnetic host crystal of known structure. 

Salihhov, S. G. Temperature dependence of paramagnetic resonance absorption of centimeter wavelength. Zh. Eksperim. i Teor. Fiz. 34, 39 (1958). 

In chemisorption, it is known that the surface atoms must have free valence electrons in order to form strong chemical bonds with gas molecules or atoms. Much recent work (15-18) using electron paramagnetic resonance absorption techniques has confirmed the presence of unpaired... 

Cohn, M., and J. Townsend A study of manganous complexes by paramagnetic resonance absorption. Nature 173, 1090 (1954). 

Tris[bis(trimethylsilyl)amido] vanadium(III) crystallizes from benzene as dark-brown, soft needles, extremely sensitive to air and moisture. This complex is paramagnetic 2.4 BM) but does not show electron paramagnetic resonance absorption at temperatures above that of liquid nitrogen. The compound is thermally unstable but gives a mass spectrum containing the parent molecular ion. Infrared spectra and electronic absorption spectra are given in Table II. The crystalline complex has the same trigonal structure as the Fe compound. ... 

Jain, P. L. Paramagnetic resonance absorption in high polymers. J. 

Fig. 3. Electron paramagnetic resonance absorption spectra of cytochrome c peroxidase and Compound ES at pH 7 and at 77°K (-------) enzyme and (—)...

In a similar way, sodium can interact with the k electrons of an aromatic compound such as naphthalene. Transfer of one electron leads to the formation of a sodium addition compound which is surprisingly stable in the presence of a few fairly specific solvents such as dimethyl ether, tetrahydrofuran, or 1,2-dimethoxyethane (26). These intensely colored sodium addition compounds have rather interesting properties. They have been shown to exhibit intense paramagnetic resonance absorptions, and hence must be assigned a charged free radical structure, as shown below (21) ... 

Fio. 11. Paramagnetic resonance absorption derivatives of (a) 1.2 wt %, (b) 3.6 wt %, and (c) 5.8 wt % reduced chromia-alumina samples at 77°K. Dashed lines separate jS-, S-, and y-phase resonances. A very weak y-phase type resonance appears in each sample (120). 

The theory of paramagnetic resonance absorption by the conduction electrons in a metal was developed at an early stage by Dyson [48] taking into account the diffusion of the electron in and out of the thin skin into which the radio-frequency (RF) field penetrates. The classical skin depth, S is given by... 

No paramagnetic resonance absorption is observed in compounds with... 

The existence of mononegative ions of aromatic hydrocarbons has been clearly demonstrated by the experiments of Lipkin et al. 17). These authors discussed the reaction of sodium metal with aromatic hydrocarbons in the presence of solvents such as 1,2-dimethoxyethane and tetrahydrofuran. They found that intensely colored solutions were formed, which exhibited strong paramagnetic resonance absorption, and concluded that free-radical ions were formed by the transfer of one electron to the aromatic compound. The reaction may be represented, using naphthalene as an example, by the equation... 

Hutchison CA, Mangum BW (1958) Paramagnetic resonance absorption in naphthalene in its phosphorescent state. J Chem Phys 29 952-953... 

Paramagnetic resonance absorption has also been observed at room temperature in aqueous solution of Ti with the following ligands Ti ligand ... 

Clyde A. Hutchison J and Weinstock B 1960 Paramagnetic resonance absorption in neptunium hexafluoride. J. Chem. Phys. 32(1), 56-61. 

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