Electron spin resonance study of nitric oxide adsorbed in NaA zeolite

Kasai, Paul H.; Gaura, R. M.

doi:10.1021/j100218a032

Cited by 35 publications

(29 citation statements)

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“…Similar species were observed in sulphated zirconia [45]. Although the spectra could be well accounted for by an S = 1 species featuring zero-field splittings, some uncertainty remained regarding the detailed structure, particularly if the NO units were arranged along a line as inferred in the original work [44]. To test this possibility, it is advantageous to treat the complex as two magnetically coupled S = 1/2 units and allow for nonparallel g-and electron-electron dipolar coupling tensors.…”

Section: B) Magnetically Coupled Cu2+-radical-radical Complexmentioning

confidence: 61%

“…NO tends to forro diamagnetic (NO)2 dimers arranged in a rectangular geometry in the solid state [43]. An unusual paramagnetic forro, first observed by Kasai et al [44] appears, however, when NaA zeolite is exposed to NO at high pressure. Thus, the X-and Q-band spectra exposed to NO at 13 kPa were assigned to a mixture of NO and (NO)2 species [22].…”

Section: B) Magnetically Coupled Cu2+-radical-radical Complexmentioning

confidence: 99%

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Applications of automatic fittings to powder EPR spectra of free radicals,S>1/2, and coupled systems

Lund

2004

Appl. Magn. Reson.

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An automatic fitting procedure has been employed to analyze experimentally studied paramagnetic complexes in powder form by electron paramagnetic resonance (EPR). A least-squares fitting procedure utilizing analytical derivatives of the theoretically calculated spectrum with respect to the g-, zero-field, nuclear quadrupole, and hyperfine tensors was used to refine those parameters. An anisotropic line width could also be fitted. The theoretically calculated spectra were obtained by matrix diagonalization of a general spin Hamiltonian allowing also magnetical[y coupled systems to be analyzed. A VO 2~ S = 1/2 complex showing g and hyperfine anisotropic interactions and free radical systems featuring Aro I =~ 0 transitions due to the direct field effect or the presence of quadrupolar nuclei have been analyzed as well as NO s species on surfaces and radiation defects employed for EPR dosimetry. Analysis of systems with S > 1/2 and magnetically coupled species has also been attempted.

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Section: B) Magnetically Coupled Cu2+-radical-radical Complexmentioning

confidence: 61%

Section: B) Magnetically Coupled Cu2+-radical-radical Complexmentioning

confidence: 99%

Applications of automatic fittings to powder EPR spectra of free radicals,S>1/2, and coupled systems

Lund

2004

Appl. Magn. Reson.

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“…= 1.99, g k = 1.86, A Y = 31 G typical for NO molecules adsorbed on Lewis acid sites of zeolites [35] can be distinguished in Fig. 4.…”

Section: Fe-nitrosyl Complexes With Intermediate Spin (S ¼ 3 2 )mentioning

confidence: 98%

Spin design of iron complexes on Fe-ZSM-5 zeolites

et al. 2005

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“…The geometric and electronic structure was instead further examined by considering previous ESR experimental and recent quantum-chemistry theoretical data. The structure proposed by Kasai et al [27] on the basis of ESR data consists of two monomeric units Na+---N-O O-N---Na + oriented along a common axis. The principal g-tensor component along this direction was observed to occur in the same direction as the maximum zero-field splitting due to the dipolar interaction between the unpaired electrons on each NO unit.…”

Section: Bonding Of (No)2 Triplet State Dimers In Zeolitesmentioning

confidence: 99%

“…At increased NO concentration a triplet-state dimer is formed. Kasai et al [27] have observed the (NO)2 tripletstate dimer in the Na-A zeolite with regular CW ESR and Yahiro et al [28][29][30] have further studied the dimer after ion exchange to replace Na + with other ions. Recent results obtained by CW and pulsed ESR, regarding the structure of a (NO)2 triplet-state dimer stabilized in a few zeolite and oxide systems are summarized here [31][32][33].…”

Section: Introductionmentioning

confidence: 99%

Structure and dynamics of radicals in zeolite matrices: ESR and theoretical studies

et al. 2003

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Amine radical cations of the type R3N "+ and [R3NCH2] "+, R = CH3, C2H5, C3H7, and nitric oxide, NO, have been used to probe the bonding to the surface and the dynamics of the radicals trapped in the confined space of cages or channels in the zeolite. Regular continuous-wave electron spin resonance (ESR) was employed to study the internal motion of the cation radicals formed by ~/-irradiation of amines and related ammonium ions, introduced during the synthesis of the zeolites A1-offretite, SAPO-37, SAPO-42 and AIPO4-5. The ESR spectra of [(CH3)3NCH2] " § radical cation in several studied systems changed reversibly with temperature, indicating dynamical effects. Free rotation about the >N-CH 2 bond of the [(CH3)3NCH2] "+ species was found to occur in the temperature range of 110 to 300 K, while the rotation about the >N-CH 3 bonds was hindered. The observations contima the theoretical prediction on the basis of density functional theory calculations, which indicate that the corresponding barriers ate of the order of 0.3 and 7 kJ/mol, respectively. The radical cations of the type R3N "+ with R = C:H 5, C3H 7 were found to undergo a different type of dynamics, involving a two-jump process of the methylene hydrogens next to the nitrogen. A cage or channel size effect on the stability and molecular dynamics was inferred in some cases. Pulsed ESR was employed to study the (NO)2 triplet-state dimers in Na-A type zeolite, with the purpose to resolve the interaction with surface groups, and to elucidate the role of the zeolite on stabilizing the triplet rather than the usual singlet state. Measurements performed at 5 K gave rise to Fourier transform spectra that were assigned to the dimer species interacting with one or more '3Na nuclei, with approximative parameters A(23Na) = (4.6, 4.6, 8.2) MHz and Q(Z3Na) = (-0.3, -0.3, 0.6) MHz for the hyperfine and nuclear quadrupote coupling tensors, respectively. The values are of similar magnitude as those determined for the NO---Na + complex. The stability of the triplet-state structure was attributed to an unusual geometric structure imposed by the zeolite matrix, with the N-O bonds along a line as in [O-N---Na+---N-O], which according to UHF ab initio calculations has a triplet ground state. 286W. Liu et al.

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Electron spin resonance study of nitric oxide adsorbed in NaA zeolite

Cited by 35 publications

References 0 publications

Applications of automatic fittings to powder EPR spectra of free radicals,S>1/2, and coupled systems

Applications of automatic fittings to powder EPR spectra of free radicals,S>1/2, and coupled systems

Spin design of iron complexes on Fe-ZSM-5 zeolites

Structure and dynamics of radicals in zeolite matrices: ESR and theoretical studies

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