Atomic Hydrogen Production from Semi-clathrate Hydrates

Koh, Dong‐Yeun; Kang, Hyery; Park, Juwoon; Shin, Woong‐Chul; Lee, Huen

doi:10.1021/ja300567b

Cited by 27 publications

(29 citation statements)

References 20 publications

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“…Photochemical production is possible (Ceppatelli et al, 2011) but most work involves radiolysis. Free hydrogen atoms have been clearly identified by electron spin resonance (ESR) spectroscopy (Yeon et al, 2008;Shin et al 2011;Koh et al, 2012) as well as various small alkyl radicals (Takeya et al, 2004(Takeya et al, , 2005a(Takeya et al, , 2005b(Takeya et al, , 2007. Of particular relevance to the current work are studies of H atom transfer from one radical to another (Ohgaki et al, 2008;Kobayashi et al, 2012;Sugahara et al, 2012;Oshima et al 2014).…”

Section: Introductionmentioning

confidence: 93%

Investigation of H atom and free radical behaviour in clathrate hydrates of organic molecules

Mozafari

Chandrasena

McKenzie

et al. 2020

Radiation Physics and Chemistry

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Clathrate hydrates are icy materials composed of a lattice of water molecules containing well-defined cavities which can accommodate small guest molecules. Their large storage capacity makes clathrates attractive media for a variety of gas storage and separation applications, but there is relatively little information on the chemical stability and diffusion of guest molecules. At the fundamental level inter-cage transition energies have been calculated, but the results need to be tested with experimental data. Ideally this should involve single-atom transport, using an isotopic tracer or spin label. Muonium (Mu = µ + e-) qualifies on both counts. As a single-electron atom with the muon as nucleus it may be considered a light isotope of hydrogen. Furthermore muonium and its reaction products may be monitored by muon spin spectroscopy. In recent years we have used this method to probe H-atom and free radical behaviour in clathrate hydrates. The current work extends studies to benzene and acetone clathrate hydrates. Of note is the simultaneous detection of muonium and muoniated radicals in the same sample. This can happen when Mu is trapped in an empty cavity, remote from its reaction partner. Increase in temperature leads to transport of Mu between cages and results in encounters with reactive guest molecules. By studying the temperature dependence of Mu and radical signals, we have been able to determine the activation energy for transport of Mu between cavities.

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Section: Introductionmentioning

confidence: 93%

Investigation of H atom and free radical behaviour in clathrate hydrates of organic molecules

Mozafari

Chandrasena

McKenzie

et al. 2020

Radiation Physics and Chemistry

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show abstract

“…Recently, clathrate hydrates have been highly valued by both theoretical and experimental researchers because of the gas storage capacity and potential applications in icy materials . In such clathrate hydrates, water molecules as host molecules form a water cage through intermolecular hydrogen bonding to wrap various guest molecules, and the distance between two adjacent cages is generally 6 to 10 Å, such a distance is likely to lead to interactions between the guest species of the clathrate hydrate cavities.…”

Section: Introductionmentioning

confidence: 99%

Intriguing electric field effect on magnetic spin couplings in dielectron clathrate hydrates

Luo

2019

Int J of Quantum Chemistry

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Clathrate hydrates have appeared as promising icy materials as the radical, high-spin molecule, and even electron clathrate hydrates are found. In particular, dielectron clathrate hydrates are expected to develop as structural units for a novel class of icy magnetic materials because of not only possible spin coupling interaction, but also very sensitive response to electric field of the loosely bound electrons. However, electric field responses concerning the magnetic properties of such hydrates have not been reported so far. In this work, three representative dielectron clathrate hydrate model clusters (e 2 @4 6 6 8 BB, e 2 @5 12 6 2 BB, and e 2 @4 6 6 8 AB) were considered for the exploration of their magnetic spin coupling properties, electron distributions, and energy responses to applied electric field. The results calculated at the density functional theory level show that the energies and electron spin coupling properties of these dielectron clathrate hydrate clusters are quite sensitive to applied electric field, presenting intriguing variations. Most importantly, applied electric field can regulate the strength of spin coupling between two trapped electrons, and even could realize the magnetic interconversion of such dielectron cluster structures between antiferromagnetic and paramagnetic or diamagnetic characteristics. Clearly, the intriguing variations should be attributed to the diffuse character, special mobility and polarizable properties of such trapped electrons, and especially the susceptible redistributions of two electrons (including the electron cloud shape and distance between two electron centers) to the electric field. This work opens up the possibility of designing novel icy magnetic materials with sensitive electric field responses of the magnetic properties. K E Y W O R D S density functional theory calculation, dielectron clathrate hydrate cluster, electric field effect, magnetic spin coupling, through electron-permeating H-bond coupling channel 1 | INTRODUCTIONRecently, clathrate hydrates have been highly valued by both theoretical and experimental researchers [1][2][3][4][5][6][7][8][9][10][11] because of the gas storage capacity and potential applications in icy materials. [9] In such clathrate hydrates, water molecules as host molecules form a water cage through intermolecular hydrogen bonding to wrap various guest molecules, and the distance between two adjacent cages is generally 6 to 10 Å, such a distance is likely to lead to interactions between the guest species of the clathrate hydrate cavities. Clathrate hydrates encapsulating free radicals, high-spin substances, charged ions, or even excess electrons (EEs) are likely to exhibit rich magnetic properties [12][13][14] and other properties. [15,16] As a

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“…Thus, hydrogen atoms have been created and studied in several clathrate systems by gamma radiolysis. [18][19][20] Similarly, small organic free radicals have been created by radiolysis at low temperature and their behaviour monitored by ESR as the temperature was raised. [21][22][23][24][25] There is clear evidence from some of these experiments of H-atom transfer from an alkyl radical in one cavity to a guest molecule in a neighbouring cage.…”

Section: Introductionmentioning

confidence: 99%

Characterization of free radicals in clathrate hydrates of pyrrole, thiophene, and isoxazole by muon spin spectroscopy

et al. 2018

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Gas hydrates have long been of interest to the petrochemical industry but there has been growing interest in potential applications for carbon dioxide sequestration and hydrogen storage. This has prompted many fundamental studies of structure and host-guest interactions, but there has been relatively little investigation of chemical reactions of the guest molecules. In previous work we have shown that it is possible to use muon spin spectroscopy to characterize H-atom-like muonium and muoniated free radicals formed in clathrate hydrates. Muonium forms in clathrate hydrates of cyclopentane and tetrahydrofuran, whereas furan and its dihydro-derivatives form radicals. The current work extends studies to clathrates hydrates of other 5-membered heterocycles: thiophene, pyrrole and isoxazole. All form structure II hydrates. In addition to the clathrates, pure liquid samples of the heterocycles were studied to aid in the assignment of radical signals and for comparison with the enclathrated radicals. Similar to furan, two distinct radicals are formed when muonium reacts with thiophene and pyrrole. However, only one muoniated radical was detected from isoxazole. Muon, proton and nitrogen hyperfine constants were determined and compared with values predicted by DFT calculations to aid the structure assignments. The results show that Mu adds preferentially to the carbon adjacent to the heteroatom in thiophene and pyrrole, and to the carbon adjacent to O in isoxazole. The same radicals are formed in clathrates, but the spectra have broader signals, suggesting slower tumbling. Furthermore, additional signals in the avoided levelcrossing spectra indicate anisotropy consistent with restricted motion of the radicals in the clathrate cages.

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Atomic Hydrogen Production from Semi-clathrate Hydrates

Cited by 27 publications

References 20 publications

Investigation of H atom and free radical behaviour in clathrate hydrates of organic molecules

Investigation of H atom and free radical behaviour in clathrate hydrates of organic molecules

Intriguing electric field effect on magnetic spin couplings in dielectron clathrate hydrates

Characterization of free radicals in clathrate hydrates of pyrrole, thiophene, and isoxazole by muon spin spectroscopy

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