Direct evidence for the glass-crystalline transformation in solid ethanol by means of a nitroxide spin probe

Kveder, Marina; Merunka, Dalibor; Ilakovac, Amon; Makarević, Janja; Jokić, Milan; Rakvin, Boris

doi:10.1016/j.cplett.2005.11.055

Cited by 16 publications

(20 citation statements)

References 22 publications

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“…The sample was deoxygenated in an argon atmosphere. Glassy and crystalline ethanol were prepared as described [1].…”

Section: Methodsmentioning

confidence: 99%

“…The sensitivity of electron paramagnetic resonance (EPR) spectroscopy to relaxation processes spanning the time scale from nanoseconds to milliseconds was exploited to characterize two different solid ethanol matrices, at 5-80 K. Incorporated paramagnetic nitroxyl radicals served as spin probe reporter groups for host matrix polymorphism [1]. As we showed previously [2], the maximal hyperfine splitting parameter, 2A max , derived from continuous wave EPR (cw-EPR) spectra discriminates between crystalline ethanol and ethanol glass.…”

Section: Introductionmentioning

confidence: 98%

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EPR study of crystalline and glassy ethanol

Kveder¹,

Merunka²,

Jokić³

et al. 2008

Journal of Non-Crystalline Solids

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“…The sample was deoxygenated in an argon atmosphere. Glassy and crystalline ethanol were prepared as described [1].…”

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

EPR study of crystalline and glassy ethanol

Kveder¹,

Merunka²,

Jokić³

et al. 2008

Journal of Non-Crystalline Solids

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“…From the apparent X-band cw-EPR rigid limit spectra, 16 maximal hyperfine splittings, 2A max , were estimated in both crystalline and glassy ethanol ͑Table I͒. That TEMPONE has a smaller hyperfine splitting than TEMPO is characteristic of the paramagnetic molecule itself, observed also in liquid ethanol.…”

mentioning

confidence: 99%

“…Glassy and crystalline states of ethanol were prepared as described. 16 It should be stressed that these two ethanol polymorphs are the most different ones 17 and regarding EPR spectroscopy could be unambiguously and reproducibly assigned from the thermal history of the spectra. EPR measurements were performed using a Bruker E-580 FT/CW X-band spectrometer equipped with an Oxford Instruments temperature unit ͑Ϯ0.1 K͒.…”

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confidence: 99%

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Electron spin-lattice relaxation in solid ethanol: Effect of nitroxyl radical hydrogen bonding and matrix disorder

et al. 2009

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The electron spin-lattice relaxation of 2,2,6,6-tetramethyl-1-piperidine-1-oxyl and 4-oxo-2,2,6,6-tetramethyl-1-piperidine-1-oxyl was measured at temperatures between 5 and 80 K in crystalline and glassy ethanol using X-band electron paramagnetic resonance spectroscopy. The experimental data at the lowest temperatures studied were explained in terms of electron-nuclear dipolar interaction between the paramagnetic center and the localized excitations, whereas at higher temperatures low-frequency vibrational modes from the host matrix and Raman processes should be considered. The strong impact of hydrogen bonding between the dopant molecule and ethanol host on the spin relaxation was observed in ethanol glass whereas in crystalline ethanol both paramagnetic guest molecules behaved similarly. DOI: 10.1103/PhysRevB.80.052201 PACS number͑s͒: 61.43.Fs, 76.30.Ϫv, 63.50.Ϫx, 65.60.ϩa Coupling of the electron spin to disorder modes of various doped matrices has been extensively studied due to the sensitivity of the approach toward dynamical properties of the observed systems.1-3 Research on disordered solids has shown that nitroxyl radicals can contribute toward the characterization of glass-forming materials, 4-6 providing experimental data for the development of self-consistent theories of molecular dynamics in glasses in general.7-10 The work presented here has been in part motivated by the lack of nitroxyl spin-lattice relaxation-time data measured below 20 K in disordered solids 11,12 and, to the best of the authors' knowledge, by the very few examples comparing paramagnetic relaxation rate data in glassy and crystalline states of the same compound. 13 Solid ethanol has been found to be a very convenient model system for the investigation of molecular solids, as it can be easily prepared in phases characterized by different types of disorder. 14,15 In our previous studies we have shown how, within the course of an X-band electron paramagnetic resonance ͑EPR͒ experiment, glassy and crystalline ethanol can be studied on the very same sample using incorporated nitroxyl radicals.5 Since nitroxyl radicals can be purposely tailored, in the context of this study we have chosen two almost identical paramagnetic probes, which differ only in one carbonyl group. We focused on the influence of hydrogen bonding between the incorporated paramagnetic guest molecule and the host matrix on the microscopic nature of probe/matrix dynamics. The central point is the comparative analysis of spin relaxation in crystalline and glassy states of the same host material. The experiments were performed in the temperature range 5-80 K, which is well below the ethanol glass transition ͑95 K͒. 14 The liquid ethanol ͓anhydrous, min. 99.8% ͑GC͒, p.a. from Kemika, Zagreb͔ and hexadeuteroethanol ͑deuteration degree Ͼ99.5% from Uvasol, Merck͒ were doped with the nitroxide paramagnetic spin-probe 2,2,6,6-tetramethyl-1-piperidine-1-oxyl ͑TEMPO͒ or 4-oxo-2,2,6,6-tetramethyl-1-piperidine-1-oxyl ͑TEMPONE͒ from Aldrich, at a concentration of 0.7 mM. Glass...

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Multifrequency Electron Spin‐Relaxation Times

Eaton

2011

Multifrequency Electron Paramagnetic Resonance

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Direct evidence for the glass-crystalline transformation in solid ethanol by means of a nitroxide spin probe

Cited by 16 publications

References 22 publications

EPR study of crystalline and glassy ethanol

EPR study of crystalline and glassy ethanol

Electron spin-lattice relaxation in solid ethanol: Effect of nitroxyl radical hydrogen bonding and matrix disorder

Multifrequency Electron Spin‐Relaxation Times

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