Open AccessDOI
Thermodynamics of some long-chain biradicals studied by EPR spectroscopy
Sornampillai Sankarapandi,J. M. Rifkind,P. T. Manoharan +2 more
- Vol. 106, Iss: 6, pp 1329-1340
TLDR
In this article, four biradicals of differing chain lengths have been prepared by spin labeling the sulphhydryl groups of dithiothreitol, and temperature-dependent EPR spectra indicate that the dynamics of these Biradicals is associated with both fast and slow exchanges of conformations.Abstract:
Four biradicals of differing chain lengths have been prepared by spin-labelling the sulphhydryl groups of dithiothreitol. Temperature-dependent EPR spectra of these biradicals indicate that the dynamics of biradicals is associated with both fast and slow exchanges of conformations. The three-conformational model incorporating cage configuration is found to be more appropriate. Certain thermodynamic parameters of conformationalchanges have been calculated from the experimental EPR parameters, obtained by the use of simulation procedures developed recently.read more
References
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TL;DR: An improved force field for molecular mechanics calculations of the structures and energies of hydrocarbons is presented in this paper, where the problem of simultaneously obtaining a sufficiently large gauche butane interaction energy while keeping the hydrogens small enough for good structural predictions was solved with the aid of onefold and twofold rotational barriers.
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TL;DR: In this article, a general theory of the nonsaturated NMR spectra of chemically exchanging molecules is formulated and a connection is made with previous theories by taking limiting expressions of the general results.
Journal ArticleDOI
Alternating linewidths. A novel relaxation process in the electron resonance of biradicals
TL;DR: In this paper, the authors considered the factors affecting the electron resonance linewidths of a biradical, showing strong spin exchange, tumbling isotropically in solution and found that the hyperfine lines should alternate in width provided the dominant relaxation mechanism is a modulation of the exchange interaction between the unpaired electrons.
Journal ArticleDOI
On the mechanism of spin exchange in long-chain nitroxide biradicals
TL;DR: In this paper, it was shown that the E.S.R. spectra of long-chain nitroxide biradicals represent the superposition of the spectrum of the non-reacting radical moieties in the elongated conformation and of the cage where the radical mixtures are close together and can interact with each other.