Room-Temperature Electron Spin Relaxation of Triarylmethyl Radicals at the X- and Q-Bands

Room-Temperature Electron Spin Relaxation of Triarylmethyl Radicals at the X- and Q-Bands Full article

Journal

Journal of Physical Chemistry B
ISSN: 1520-6106

Output data

Year: 2015, Volume: 119, Number: 43, Pages: 13630-13640 Pages count : 11 DOI: 10.1021/acs.jpcb.5b03027

Authors

Kuzhelev Andrey A. ^2,3 , Trukhin Dmitry V. ^2,3 , Krumkacheva Olesya A. ^1,3 , Strizhakov Rodion K. ² , Rogozhnikova Olga Yu. ^2,3 , Troitskaya Tatiana I. ^2,3 , Fedin Matvey V. ^1,3 , Tormyshev Victor M. ^2,3 , Bagryanskaya Elena G. ^2,3

Affiliations

1	(Данные Web of science) RAS, SB, Int Tomog Ctr, Novosibirsk 630090, Russia
2	(Данные Web of science) RAS, SB, NN Vorozhtsov Novosibirsk Inst Organ Chem, Novosibirsk 630090, Russia
3	(Данные Web of science) Novosibirsk State Univ, Novosibirsk 630090, Russia

Triarylmethyl radicals (trityls, TAMs) represent a relatively new class of spin labels. The long relaxation of trityls at room temperature in liquid solutions makes them a promising alternative for traditional nitroxides. In this work we have synthesized a series of TAMs including perdeuterated Finland trityl (D-36 form), mono-, di-, and triester derivatives of Finland-D-36 trityl, the deuterated form of OX63, the dodeca-n-butyl homologue of Finland trityl, and triamide derivatives of Finland trityl with primary and secondary amines attached. We have studied room-temperature relaxation properties of these TAMs in liquids using pulsed electron paramagnetic resonance (EPR) at two microwave frequency bands. We have found the clear dependence of phase memory time (T-m similar to T-2) on the magnetic field: room-temperature T-m values are similar to 1.5-2.5 times smaller at the Q-band (34 GHz, 1.2 T) than at the X-band (9 GHz, 0.3 T). This trend is ascribed to the contribution from g-anisotropy that is negligible at lower magnetic fields but comes into play at the Q-band. In agreement with this, the difference between T-1 and T-m becomes more pronounced at the Q-band than at the X-band due to increased contributions from incomplete motional averaging of g-anisotropy. Linear dependence of (1/T-m - 1/T-1) on viscosity implies that g-anisotropy is modulated by rotational motion of the trityl radical. On the basis of the analysis of previous data and results of the present work, we conclude that, in the general situation where the spin label is at least partly mobile, the X-band is most suitable for application of trityls for room-temperature pulsed EPR distance measurements.

Kuzhelev A.A. , Trukhin D.V. , Krumkacheva O.A. , Strizhakov R.K. , Rogozhnikova O.Y. , Troitskaya T.I. , Fedin M.V. , Tormyshev V.M. , Bagryanskaya E.G.
Room-Temperature Electron Spin Relaxation of Triarylmethyl Radicals at the X- and Q-Bands

Journal of Physical Chemistry B. 2015. V.119. N43. P.13630-13640. DOI: 10.1021/acs.jpcb.5b03027 WOS Scopus РИНЦ

Full text from publisher

Published online:	Jun 4, 2015
Published print:	Oct 29, 2015

Web of science	WOS:000363994000018
Scopus	2-s2.0-84946043825
Elibrary	24968242
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