Solvent and Temperature Dependence of Spin Echo Dephasing for Chromium(V) and Vanadyl Complexes in Glassy Solution |
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| Institution: | 1. Department of Mathematics and Science Education, Nevşehir Hacı Bektaş Veli University, 50300, Nevşehir, Turkey;2. Department of Electronics and Automation, Ahi Evran University, 40100, Kırşehir, Turkey;1. Department of Chemistry, Taras Shevchenko National University, 64/13, Volodymyrska Street, Kyiv, 01601, Ukraine;2. National Academy of Science of Ukraine, STC “Institute for Single Crystals”, Khar’kov, Ukraine;1. Laboratoire d’Elaboration et Caractérisation Physico Mécanique et Métallurgique des Matériaux (ECP3M), Département de Génie Electrique, Faculté des Sciences et de la Technologie, Université Abdelhamid Ibn Badis de Mostaganem, 27000 Mostaganem, Algeria;2. Aix-Marseille Université, IM2NP-CNRS UMR 7334, Campus St. Jérôme, Case 142, 13397 Marseille Cedex 20, France;3. Laboratoire de physique computationnelle des matériaux (LPCM), Djillali Liabès University of Sidi Bel-Abbès, 22000, Algeria;1. Department of Chemistry, Indian Institute of Technology Bombay, Mumbai 400076, India;2. School of Science and the Environment, Division of Chemistry, Manchester Metropolitan University, Manchester, UK;3. School of Chemistry, Monash University, Clayton, Victoria 3800, Australia |
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| Abstract: | The solvent and temperature dependence of the rate constant for spin echo dephasing, 1/Tm, for 0.2 to 1.2 mM glassy solutions of chromyl bis(1-hydroxy-cyclohexanecarboxylic acid), CrO(HCA)−2; aquo vanadyl ion, VO2+(aq), and vanadyl bis(trifluoroacetylacetonate), VO(tfac)2were examined. At low temperatures where 1/T1⪡ 1/Tm, 1/Tmin 1:1 H2O:glycerol is dominated by solvent protons. At low temperature 1/Tmincreases in the order 1:1 H2O:glycerol or 9:1 CF3CH2OH:ethyleneglycol (no methyl groups) < 9:1i-PrOH:MeOH (hindered methyl groups) < 9:1n-PrOH:MeOH (less hindered methyl groups). This solvent dependence of 1/Tmis similar to that observed for nitroxyl radicals, which indicates that the effect of solvent methyl groups on spin-echo dephasing at low temperature is quite general. At higher temperatures the echo dephasing is dominated by spin–lattice relaxation and is concentration dependent. As the glass softens, echo dephasing is dominated by the onset of molecular tumbling. |
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