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Nishikiori, Shin-ichi; Soma, Tomoaki; Iwamoto, Toschitake

doi:10.1023/a:1007968716019

Cited by 19 publications

(17 citation statements)

References 11 publications

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“…Exchange rates are determined by visually matching the experimental data with the simulated spectra. We calculate the model shape using the program reported by Nishikiori et al 31 with a quadrupolar coupling constant ͑QCC͒ determined from spectra acquired in the slow exchange regime and a model that considers site exchange of the 2 H nuclei by 180°rotations. The only adjustable parameters are the site-exchange rate k r and the population difference at each of the two nonequivalent sites, which is determined by the asymmetry parameter S, as defined in Fig.…”

Section: B Solid State 2 H Nmr Measurementsmentioning

confidence: 99%

Dipolar rotor-rotor interactions in a difluorobenzene molecular rotor crystal

et al. 2006

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In this paper, we characterize the rotational dynamics and observe rotor-rotor interactions within a crystalline, three-dimensional array of dipolar molecular rotors. The rotating portion of each rotor molecule consists of a dipolar fluorine-substituted phenyl group. The phenyl rotors are connected by acetylene linkages to bulky triphenyl methyl groups which are held rigid in the crystal lattice. These custom synthesized rotor molecules allow control over the molecular spacing in the lattice, the dipole strength, and the rotational hindrance, thus permitting formation of systems with rapid thermal rotation and strong dipole-dipole interactions, which is of interest for studying new phases and collective phenomena. Dielectric and 2 H NMR spectroscopy measurements are used to map the rotational potential, and to explore the influence of rotor-rotor interactions. Interactions due to dipole-dipole effects are studied using a Monte Carlo simulation, while contributions from steric interactions between rotors are investigated using molecular mechanics methods. Both contributions are needed explain the dielectric spectroscopy results.

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Section: B Solid State 2 H Nmr Measurementsmentioning

confidence: 99%

Dipolar rotor-rotor interactions in a difluorobenzene molecular rotor crystal

et al. 2006

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“…For our studies, we take advantage of the well-characterized spectral changes occurring upon rotation of phenylene groups about their 1,4-axis, typically by 180°angular displacement, which are commonly referred to as phenylene flips. 13,14 An isotopically labeled sample of 3-d 4 for dynamic NMR was prepared as shown in Scheme 1 using 1,4-dibromobenzene-d 4 . The spectra were acquired with a quadrupole echo pulse sequence 15 with a 90°pulse of 2.25 µs, with echo and refocusing delays of 50 and 40 µs, respectively.…”

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confidence: 99%

Improved Physical Properties and Rotational Dynamics in a Molecular Gyroscope with an Asymmetric Stator Structure

2006

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[structure: see text] A molecular gyroscope consisting of a 1,4-diethynylphenylene rotator linked to trityl and triptycyl groups (3) showed significantly improved physical properties and faster rotational dynamics than analogous symmetric bis(trityl) (1) or bis(triptycyl) (2) structures. An activation energy of 7.9 kcal/mol for 3 was determined by 2H NMR. This is ca. 4-6 kcal/mol lower than that of compound 1. The different dynamics of the three compounds can be qualitatively understood in terms of their different packing coefficients.

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“…The line shape simulation was performed using our original program, which was written in our previous studies of guest molecular motions. 9 The value of the Quadrupole Coupling Constant (QCC) was set to 163(2) kHz and the asymmetry parameter (g) to zero for the 1,4-dioxane molecule in a static state in our simulations. These values were obtained from a 2 H-NMR powder pattern observed on neat C 4 D 8 O 2 at 203 K.…”

Section: Single Crystal X-ray Diffractionmentioning

confidence: 99%

“…For simulating powder patterns in an intermediate speed region, numerical calculation is necessary. 9,11 This simulation was carried out by varying the jump rate for the ring inversion and that for the rotational motion independently. The results are shown in Fig.…”

Section: Dynamics Of 14-dioxanementioning

confidence: 99%

Crystal structure and dynamic properties of a bimetallic cyano complex Cd(C4H8O2)Cu(CN)3 with an interpenetrating 3D framework containing a 1,4-dioxane bridging ligand as a rotor

Sato

Nishikiori

2007

Dalton Trans.

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The title complex Cd(C(4)H(8)O(2))Cu(CN)(3) has a 3D twofold interpenetrating framework structure. The structural base of the framework is a planar hexagonal network complex of [Cu(CN)(3)Cd](infinity) ,which is formed with cyanides connecting the coordination sites of Cu(i) ions with a triangle planar form and the equatorial coordination sites of Cd(ii) ions with a trigonal bipyramid form. The networks are stacked and a 1,4-dioxane molecule coordinates to two Cd(ii) ions in alternate networks as a bridging ligand. The 1,4-dioxane ligand penetrates a hexagonal window of the network sandwiched between the bridged networks. This 1,4-dioxane bridge completes the 3D twofold interpenetrating framework structure. (2)H-NMR powder patterns of the deuterated complex Cd(C(4)D(8)O(2))Cu(CN)(3) revealed the dynamics of the 1,4-dioxane bridge as a rotor. Above 253 K, the 1,4-dioxane ligand undergoes rotational motion combined with a ring inversion between two chair conformations. The free energy of activation DeltaG(double dagger) for the ring inversion was calculated to be 41.4(7) kJ mol(-1) at 298 K.

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Cited by 19 publications

References 11 publications

Dipolar rotor-rotor interactions in a difluorobenzene molecular rotor crystal

Dipolar rotor-rotor interactions in a difluorobenzene molecular rotor crystal

Improved Physical Properties and Rotational Dynamics in a Molecular Gyroscope with an Asymmetric Stator Structure

Crystal structure and dynamic properties of a bimetallic cyano complex Cd(C4H8O2)Cu(CN)3 with an interpenetrating 3D framework containing a 1,4-dioxane bridging ligand as a rotor

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