Molecular motion of benzene, n-hexane, and cyclohexane in potassium zeolite L studied by deuterium NMR

Silbernagel, B. G.; Garcia, Armando R.; Newsam, J. M.; Hulme, R.

doi:10.1021/j100354a044

Cited by 47 publications

(37 citation statements)

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“…This suggests that the molecule sits close enough to the channel walls so that the aromatic 6‐rings can interact with the zeolite's counterions (K + ). Experimental results and calculations have shown that the preferred adsorption sites for benzene in zeolite L are the counterions located in the channel walls 34–37. Such a position would result in a slight hindrance of these motions and an increase of the energy needed to activate them.…”

Section: Discussionmentioning

confidence: 99%

Electronic and Vibrational Properties of Fluorenone in the Channels of Zeolite L

Devaux

Minkowski

Calzaferri

2004

Chemistry A European J

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Fluorenone (C13H8O) was inserted into the channels of zeolite L by using gas-phase adsorption. The size, structure, and stability of fluorenone are well suited for studying host-guest interactions. The Fourier transform IR, Raman, luminescence, and excitation spectra, in addition to thermal analysis data, of fluorenone in solution and fluorenone/zeolite L are reported. Normal coordinate analysis of fluorenone was performed, based on which IR and Raman bands were assigned, and an experimental force field was determined. The vibrational spectra can be used for nondestructive quantitative analysis by comparing a characteristic dye band with a zeolite band that has been chosen as the internal standard. Molecular orbital calculations were performed to gain a better understanding of the electronic structure of the system and to support the interpretation of the electronic absorption and luminescence spectra. Fluorenone shows unusual luminescence behavior in that it emits from two states. The relative intensity of these two bands depends strongly on the environment and changes unexpectedly in response to temperature. In fluorenone/zeolite L, the intensity of the 300 nm band (lifetime 9 micros) increases with decreasing temperature, while the opposite is true for the 400 nm band (lifetime 115 micros). A model of the host-guest interaction is derived from the experimental results and calculations: the dye molecule sits close to the channel walls with the carbonyl group pointing to an Al3+ site of the zeolite framework. A secondary interaction was observed between the fluorenone's aromatic ring and the zeolite's charge-compensating cations.

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Section: Discussionmentioning

confidence: 99%

Electronic and Vibrational Properties of Fluorenone in the Channels of Zeolite L

Devaux

Minkowski

Calzaferri

2004

Chemistry A European J

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“…Nuclear magnetic resonance (NMR) measurements of hydrocarbon mobility in zeolites show that the rates of conformational changes are significantly slower than in the bulk (64). Picosecond measurements of reorientation times support this, showing moderately slower relaxation times (by a factor of 3) when a polar molecule (nitroben-zene) adsorbs to porous glass (65).…”

Section: Other Probes Of Surface Dynamicsmentioning

confidence: 97%

Motions and Relaxations of Confined Liquids

Granick

1991

Science

951

697

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When a liquid is confined in a narrow gap (as near a cell membrane, in a lubricated contact between solids, or in a porous medium), new dynamic behavior emerges. The effective shear viscosity is enhanced compared to the bulk, relaxation times are prolonged, and nonlinear responses set in at lower shear rates. These effects are more prominent, the thinner the liquid film. They appear to be the manifestation of collective motions. The flow of liquids under extreme confinement cannot be understood simply by intuitive extrapolation of bulk properties. Practical consequences are possible in areas from tribology and materials processing to membrane physics.

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“…These values are (g Q ) consistent with the results of Silbernagel et al (93.0 kHz). 13 The QCC value is approximately half of that in rigid state kHz). 16 Solid also shows the (QCC 0 \ 193 ^3 benzene-d 6 half value above 135 K. 16,17 The benzene ring undergoes a fast rotation around the axis, while the ring plane is C 6 Ðxed.…”

Section: Benzenementioning

confidence: 99%

“…The mutual exchange is restricted. In the case of benzene/silicalite, spectral simulation has been performed assuming the presence of three components, but without presenting the detailed results of the simulation.8 Silbernagel et al 13 have studied the molecular motions of benzene, n-hexane and cyclohexane in KL zeolite. They discussed the mode of motion from the line shape qualitatively, and estimated the activation energy of the motion for and n-hexane-from the temperature depen-benzene-d 6 d 14 dence of the spinÈlattice relaxation time, Since the time T 1 .…”

Section: Introductionmentioning

confidence: 99%