Deuterium nuclear magnetic resonance study of several cyclophosphazene inclusion compounds: guest conformation, dynamics, and intrachannel orientation

Meirovitch, Eva; Belsky, Igal

doi:10.1021/j150663a024

Cited by 10 publications

(8 citation statements)

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“…The derived absolute orientation of the trioxane guests is a direct consequence of the spatial constraints imposed by the cyclophosphazene lattice, as can be deduced from an inspection of the molecular dimensions of the trioxane guests and the cyclophosphazene host channel diameter. This is in agreement with a former 2 H NMR study on the benzene/cyclophosphazene inclusion compound, , in which the molecular C 6 -axes of the benzene guests also were found to be oriented perpendicular with respect to the host channel long axis.…”

Section: Resultssupporting

confidence: 92%

“…So far, only a few X-ray studies for cyclophosphazene inclusion compounds are known. , They showed that the host latticein analogy to the urea and thiourea inclusion compoundsis characterized by hexagonal channels. Likewise, 2 H NMR studies have been published on cyclophosphazene inclusion compounds with benzene and related compounds, which again revealed a high mobility of such guest molecules in the cyclophosphazene channels. − …”

Section: Introductionmentioning

confidence: 96%

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The Molecular Behavior of 1,3,5-Trioxane in a Cyclophosphazene Inclusion Compound: A²H NMR Study

2002

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Dynamic 2 H NMR techniques were employed to examine the ordering behavior and dynamics of perdeuterated 1,3,5-trioxane-d 6 in the inclusion compound with tris-(1,2-dioxyphenyl)-cyclotriphosphazene. The experimental data, obtained by variable-temperature line shape studies, spin-spin and spin-lattice relaxation, and 2D exchange experiments between 30 and 370 K, were analyzed in a quantitative way by carrying out theoretical calculations on the basis of various motional models. At room temperature, highly mobile trioxane guests are observed. They undergo various overall and conformational motions that give rise to a substantial orientational disorder within the hexagonal cyclophosphazene channels. For the present inclusion compound, the following guest motions could be assigned: (i) molecular rotation about the molecular C 3 -axis of the guests (rotational diffusion process), (ii) rotation about the host channel symmetry axis (3-fold jump process), (iii) overall fluctuation, and (iv) ring inversion. It could be shown that the two symmetry axes for rotational motions are oriented perpendicular to each other, that is, the C 3 -axes of the trioxane guests are inclined at an angle of 90°w ith respect to the channel long axis. The activation energies for the overall rotations were found to be rather low with values of 10.0 and 10.9 kJ/mol for the motion about the C 3 -axis and channel long axis, respectively. For the ring inversion process, an activation energy of 50.0 kJ/mol was derived that is almost identical with the values reported from previous solution NMR studies.

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Section: Resultssupporting

confidence: 92%

Section: Introductionmentioning

confidence: 96%

The Molecular Behavior of 1,3,5-Trioxane in a Cyclophosphazene Inclusion Compound: A²H NMR Study

2002

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“…can be incorporated, whereas thiourea channels have a preference toward bulkier guests, such as cycloalkanes and substituted cycloalkanes. , Up to now, numerous studies have been reported on urea and thiourea systems that have explored the thermal and structural properties of the host lattice as well as the dynamic features of the guest species. − The earlier information primarily was deduced from X-ray diffraction, differential scanning calorimetry (DSC), FT IR or NMR spectroscopy, − whereas solid-state NMR techniques ,− were employed for the evaluation of the guest dynamics in such inclusion compounds. Among these, 2 H NMR methods have demonstrated their particular suitability for the characterization of the molecular guests in such inclusion compounds, yielding information about the molecular conformation, local ordering, and order−disorder phenomena, as well as intra- and intermolecular guest motions. − …”

Section: Introductionmentioning

confidence: 99%

Solid-State²H NMR Studies of Cyclophosphazene Inclusion Compounds: Order and Dynamics of the Benzene Guests

Villanueva-Garibay

Müller

2004

J. Phys. Chem. B

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Variable-temperature 2 H NMR investigations were been carried out to study the molecular behavior of perdeuterated benzene in the inclusion compound with tris(1,2-dioxyphenyl)cyclotriphosphazene. A comprehensive variable-temperature 2 H NMR study is presented comprising line shape studies and spin-spin and spin-lattice relaxation experiments. The experimental data clearly indicate the presence of highly mobile guest species at room temperature. Sample cooling gives rise to characteristic line shape effects at around 140 K that can be attributed to a slowing of the rotational motion (nondegenerate three-fold jump processes) of the guest species about the cyclophosphazene channel long axis. The rotation of the benzene molecules about their molecular C 6 axes can be followed to even lower temperatures (∼40 K). A quantitative analysis of the experimental data is achieved by appropriate computer simulations taking into account various motions of the benzene guests. The derived activation energies for the overall rotations are rather small with values of 5.4 ( 0.3 and 4.2 ( 0.1 kJ/mol for motion about the channel long axis and 2.1 ( 0.1 kJ/mol for rotation about the molecular C 6 axis. However, these values are larger than those reported earlier for aliphatic cyclic guests, which directly points to stronger nonbonded guest-host interactions in the present systems. The guest ordering is described by an almost perpendicular orientation of the benzene C 6 axis with respect to the cyclophosphazene channel long axis. The ordering of the benzene guests, which is reduced by fast overall fluctuations of small amplitude, is substantially higher than that observed in related systems, which again can be attributed to the aforementioned guest-host interactions.

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“…Recently, various studies dealing with the molecular dynamics of differ-ent guest molecules included in cyclophosphazene host component have been reported. [15][16][17][18][19][20] Solid state NMR spectroscopy is known to be very suitable for obtaining detailed information about molecular conformation, local ordering, order-disorder phenomena and motional features in molecular solids. 4,[21][22][23][24] Among these, dynamic 2 H NMR methods have been shown to be particularly suitable for the characterization of the motional features in solid materials, especially including the dynamics of the guests in various types of inclusion compounds.…”

Section: Introductionmentioning

confidence: 99%

“…4,[21][22][23][24] Among these, dynamic 2 H NMR methods have been shown to be particularly suitable for the characterization of the motional features in solid materials, especially including the dynamics of the guests in various types of inclusion compounds. 15,17,20,[25][26][27][28][29][30] Moreover, by variable temperature studies it is possible to follow different types of molecular processes over a large temperature range and thus different time scales.…”

Section: Introductionmentioning

confidence: 99%

Molecular dynamics and ordering of pyridine in its cyclophosphazene inclusion compound as evaluated by solid state 2H NMR spectroscopy

Villanueva-Garibay

Müller

2006

Phys. Chem. Chem. Phys.

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Variable temperature 2H NMR experiments (line shape analysis, relaxation studies) were carried out on the pyridine-d5-tris-(1,2-dioxyphenyl)-cyclotriphosphazene inclusion compound in the temperature range between 110-300 K. It is found that the pyridine guests are highly mobile throughout the whole temperature range covered here. The observation of three superimposed 2H NMR signals can be understood in terms of a particular (motionally averaged) orientation of the pyridine molecules, which is a consequence of the molecular symmetry of the pyridine guests and the imposed channel restrictions. The experimental data are consistent with a combined rotation on cone-small angle fluctuation model, which assumes a fast molecular reorientation between two superimposed cones with an opening angle for the inner cone between 59-73 degrees (angle of fluctuation between 1-3 degrees ). On the basis of this model assumption it is possible to reproduce both the experimental 2H NMR line shapes and the spin-lattice relaxation data in a quantitative way. The analysis of the partially relaxed spectra (inversion recovery experiments) yields the correlation times for this overall motional process. They follow an Arrhenius behavior from which an activation energy of 8.7 +/- 0.4 kJ mol(-1) is derived. The results are discussed in the framework of the published data for related systems.

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Deuterium nuclear magnetic resonance study of several cyclophosphazene inclusion compounds: guest conformation, dynamics, and intrachannel orientation

Cited by 10 publications

References 0 publications

The Molecular Behavior of 1,3,5-Trioxane in a Cyclophosphazene Inclusion Compound: A²H NMR Study

The Molecular Behavior of 1,3,5-Trioxane in a Cyclophosphazene Inclusion Compound: A²H NMR Study

Solid-State²H NMR Studies of Cyclophosphazene Inclusion Compounds: Order and Dynamics of the Benzene Guests

Molecular dynamics and ordering of pyridine in its cyclophosphazene inclusion compound as evaluated by solid state 2H NMR spectroscopy

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Deuterium nuclear magnetic resonance study of several cyclophosphazene inclusion compounds: guest conformation, dynamics, and intrachannel orientation

Cited by 10 publications

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The Molecular Behavior of 1,3,5-Trioxane in a Cyclophosphazene Inclusion Compound: A2H NMR Study

The Molecular Behavior of 1,3,5-Trioxane in a Cyclophosphazene Inclusion Compound: A2H NMR Study

Solid-State2H NMR Studies of Cyclophosphazene Inclusion Compounds: Order and Dynamics of the Benzene Guests

Molecular dynamics and ordering of pyridine in its cyclophosphazene inclusion compound as evaluated by solid state 2H NMR spectroscopy

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The Molecular Behavior of 1,3,5-Trioxane in a Cyclophosphazene Inclusion Compound: A²H NMR Study

The Molecular Behavior of 1,3,5-Trioxane in a Cyclophosphazene Inclusion Compound: A²H NMR Study

Solid-State²H NMR Studies of Cyclophosphazene Inclusion Compounds: Order and Dynamics of the Benzene Guests