. Author manuscript; available in PMC: 2015 Oct 1.

Published in final edited form as: J Magn Reson. 2014 Sep 9;247:81–87. doi: 10.1016/j.jmr.2014.08.014

Table 3. Frequency Dependence of Relaxation Times and Mechanisms for Representative Trityl, Semiquinone, and Nitroxide Radicals.

Radical^a	Solvent	9 GHz			250 MHz			Ref.
Radical^a	Solvent	T₁ (μs)	1/T₁ (μs)^-1	mechanism	T₁ (μs)	1/T₁ (μs)^-1	mechanism
Trityl-OX31	H₂O^b	14	0.071	local mode	5.9	0.17	modulation of proton dipole interactions by trityl tumbling	[21]
Trityl-CH₃	H₂O^b	16	0.062	local mode	7.9	0.13	modulation of proton dipole interactions by trityl tumbling	[21]
25DTBSQ	C₂H₅OH	7.8	0.13	spin rotation + local mode	3.4	0.29	modulation of solvent proton interactions by solvent motion	This work
25DTBSQ	CH₃OH	5.0	0.20	spin rotation + local mode	3.4	0.29	modulation of solvent proton interactions by solvent motion	This work
Tempone-d₁₆	69% glycerol^b	2.2	0.45	modulation of A^d	0.25^e	4.0^e	modulation of A^d	[23]
Tempone-d₁₆	H₂O^c	0.58	1.7	spin rotation + modulation of A^d	0.60	1.7	spin rotation + modulation of A^d	[22, 23]

Abbreviations for radicals are defined in the papers cited

0.2 mM concentration

0.5 mM concentration

A refers to the nitrogen hyperfine coupling

Measured at 630 MHz