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Site Directed Spin Labeling and EPR Spectroscopic Studies of Pentameric Ligand-Gated Ion Channels
Published on: July 4, 2016
Electron spin relaxation properties of atomic hydrogen encapsulated in octavinyl POSS cages
George Mitrikas1, Stavroula Menenakou1
1Institute of Nanoscience and Nanotechnology, N.C.S.R. Demokritos, 15310 Athens, Greece. g.mitrikas@inn.demokritos.gr.
Abstract:
The electron spin relaxation times of encapsulated atomic hydrogen in the vinyl derivative of silsesquioxane (R8Si8O12) cages (R = CH[double bond, length as m-dash]CH2) are studied in detail by pulse electron paramagnetic resonance (EPR) methods in the temperature range between 10 and 300 K. The temperature dependence of the spin-lattice relaxation time, T1, shows similar behaviour with previously studied derivatives that typically involve Raman and thermally activated processes. The room-temperature phase-memory time TM = 9 μs is comparable to those reported for different alkyl derivatives and exhibits a characteristic temperature dependence with a considerable reduction below 200 K as a result of dynamic effects like methyl group rotation. However, this reduction is modest for the vinyl derivative since the minimum observed TM = 5 μs is much longer than the value of 1 μs reported for methyl-containing derivatives like R = C2H5, C3H7 (n-propyl), or OSi(CH3)2H. This discrepancy is attributed to the different rotation dynamics of the vinyl group, as evidenced by the determined activation energy and rotation frequency.
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