Reorientation of benzene in its crystalline state: A model case for the analogy between nuclear magnetic resonance spin alignment and quasielastic incoherent neutron scattering

Fujara, F.; Petry, W.; Schnauss, W.; Sillescu, H.

doi:10.1063/1.455127

Cited by 43 publications

(24 citation statements)

References 13 publications

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“…The rotary dynamics of the benzene molecules in the solvent clathrate of 2 was also investigated by 2 H NMR with crystals grown from C 6 D 6 (34). In agreement with previous studies (36,37) and as expected for a volume-conserving process, benzene molecules were found to undergo in-plane whole-body rotations described by 60°jumps with rate constants exceeding 10 8 s Ϫ1 , even at 200 K.…”

Section: Rotational Dynamics In Crystalssupporting

confidence: 57%

Crystalline Molecular Machines: Encoding Supramolecular Dynamics into Molecular Structure

Garcia‐Garibay

2005

ChemInform

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Crystalline molecular machines represent an exciting new branch of crystal engineering and materials science with important implications to nanotechnology. Crystalline molecular machines are crystals built with molecules that are structurally programmed to respond collectively to mechanic, electric, magnetic, or photonic stimuli to fulfill specific functions. One of the main challenges in their construction derives from the picometric precision required for their mechanic operation within the close-packed, self-assembled environment of crystalline solids. In this article, we outline some of the general guidelines for their design and apply them for the construction of molecular crystals with units intended to emulate macroscopic gyroscopes and compasses. Recent advances in the preparation, crystallization, and dynamic characterization of these interesting systems offer a foothold to the possibilities and help highlight some avenues for future experimentation.crystal engineering ͉ molecular gyroscopes ͉ crystal dynamics ͉ molecular rotors T he design and construction of artificial mechanomolecular machines is one of the most interesting scientific challenges of our times (1, 2), and a deeper understanding of structure-property relations in several biological motors (3, 4) have led to considerable insights in the past few years. However, the formulation, design, and materialization of truly serviceable artificial molecular machines remains a major challenge. Whereas initial efforts have been centered on isolated molecules randomly tumbling in solution, most biomolecular systems and macroscopic machines are complex, multiple-component, densely packed assemblies, supported on membranes or within the bulk of larger structures.In this Perspective, I will describe our group's recent efforts on a quest to control the structure and dynamics of closed-packed molecular assemblies. Our thesis is based on the premise that information contained at the molecular level in the form of topology, size, shape, nonbonding interactions, electronic structure, etc. will dictate the aggregation, dynamics, actuation possibilities, and mechanical functions. One of our initial goals is to uncover the relation between supramolecular structure and intermolecular dynamics by taking advantage of dynamic stereochemistry, self-assembly, and crystal engineering. To document this relation with as high precision and certainty as possible, we have chosen the crystalline solid state as a promising model. Structural characterizations can be carried out by singlecrystal x-ray diffraction measurements, and dynamic properties can be determined over a wide range of time scales by techniques that include variabletemperature solid-state NMR, dielectric spectroscopy, and inelastic neutron scattering, among several others. From Molecular Structure Information to Self-Assembly and DynamicsA machine is defined as ''an assemblage of parts that transmits forces, motion, or energy from one to another in a predetermined manner'' (5). Not explicit in the dictionary'...

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Section: Rotational Dynamics In Crystalssupporting

confidence: 57%

Crystalline Molecular Machines: Encoding Supramolecular Dynamics into Molecular Structure

Garcia‐Garibay

2005

ChemInform

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“…In principle, detailed analysis of F ss ∞ (t p ) can provide quantitative information about the overall geometry of the anisotropic rotational motion. 39,50 Here, we do not adopt this approach since exact determination of the plateau height is difficult in our case where the width of the decay exceeds the dynamic range of the experiment. Nevertheless, further semi-quantitative insight is available from our result that F ss ∞ continuously decreases when the evolution time is extended.…”

Section: Stimulated-echo Experimentsmentioning

confidence: 99%

2H NMR studies of glycerol dynamics in protein matrices

Herbers

Sauer

Vogel

2012

The Journal of Chemical Physics

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We use (2)H NMR spectroscopy to investigate the rotational motion of glycerol molecules in matrices provided by the connective tissue proteins elastin and collagen. Analyzing spin-lattice relaxation, line-shape properties, and stimulated-echo decays, we determine the rates and geometries of the motion as a function of temperature and composition. It is found that embedding glycerol in an elastin matrix leads to a mild slowdown of glycerol reorientation at low temperatures and glycerol concentrations, while the effect vanishes at ambient temperatures or high solvent content. Furthermore, it is observed that the nonexponential character of the rotational correlation functions is much more prominent in the elastin matrix than in the bulk liquid. Results from spin-lattice relaxation and line shape measurements indicate that, in the mixed systems, the strong nonexponentiality is in large part due to the existence of distributions of correlation times, which are broader on the long-time flank and, hence, more symmetric than in the neat system. Stimulated-echo analysis of slow glycerol dynamics reveals that, when elastin is added, the mechanism for the reorientation crosses over from small-angle jump dynamics to large-angle jump dynamics and the geometry of the motion changes from isotropic to anisotropic. The results are discussed against the background of present and previous findings for glycerol and water dynamics in various protein matrices and compared with observations for other dynamically highly asymmetric mixtures so as to ascertain in which way the viscous freezing of a fast component in the matrix of a slow component differs from the glassy slowdown in neat supercooled liquids.

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“…From our simulations, we obtain u 2 equal to 0.66 Å 2 for benzene at 270 K and to 0.80 Å 2 for (PyH)I at 290 K. As mentioned above QENS data for benzene and pyridinium iodide at different temperatures are available in the literature. 16,30 For benzene at 210 K, 246 K (Fig. 6), and 273 K and for (PyH)I at 296 K and 270 K (high temperature phase) the authors found that the QENS spectra are best fitted by a sixfold rotational model between equivalent sites on a circle of radius r in the molecular plane.…”

Section: Benzene and Pyridinium Iodidementioning

confidence: 97%

“…The same geometry of motion has been proposed earlier on the basis of NMR 15,38,39 and QENS data. 16,30 As the QENS experiment is particularly sensitive to the geometry of motion, a stringent test of the simulations consist in comparing the experimental EISF (EISF experim = A 0 (Q)) with that extracted from the simulated trajectories (EISF simulated ). EISF simulated were calculated directly in nMoldyn 40 using the expression: 28…”

Section: Benzene and Pyridinium Iodidementioning

confidence: 99%

“…Benzene molecules and pyridinium cations in the high temperature phase of (PyH)I) reorient between six equivalent minima. 15,16,30 However, in the low-temperature phase, the pyridinium cation jumps between potential minima having different energies. Finally, in the case of the pyridinium cation in (PyH)NO 3 its reorientation takes place between non-equivalent positions-at all temperatures studied.…”

Section: Introductionmentioning

confidence: 99%

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Dynamics in molecular and molecular-ionic crystals: A combined experimental and molecular simulation study of reorientational motions in benzene, pyridinium iodide, and pyridinium nitrate

Pajzderska

Ma²,

Wąsicki

2013

The Journal of Chemical Physics

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Molecular dynamics (MD) simulations for crystalline benzene (C(6)H(6)), pyridinium iodide [C(5)NH(6)](+)I(-), and pyridinium nitrate [C(5)NH(6)](+)NO(3)(-) have been performed as a function of temperature and pressure. Despite the similar shape of the benzene molecule and the pyridinium cation, the experimental and simulated data have showed clear differences in their dynamics. Therefore, the rotational dynamics have been explored in detail by comparing thoroughly the existing experimental results together with new quasielastic neutron scattering (QENS) data obtained for (PyH)NO(3) and molecular dynamics simulations. The correlation times, activation energy, geometry of motion of benzene molecule and pyridinium cation, isothermal compressibility, and activation volume obtained from the simulations are compared with the experimental results obtained by nuclear magnetic resonance and QENS methods. MD simulations have also revealed that reorientation of the pyridinium cation in pyridinium nitrate between two inequivalent positions is strongly affected by the hydrogen bond N-H···O between the cation and the anion and the influence of temperature on strength of the hydrogen bond is much more important than that of the pressure.

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Reorientation of benzene in its crystalline state: A model case for the analogy between nuclear magnetic resonance spin alignment and quasielastic incoherent neutron scattering

Cited by 43 publications

References 13 publications

Crystalline Molecular Machines: Encoding Supramolecular Dynamics into Molecular Structure

Crystalline Molecular Machines: Encoding Supramolecular Dynamics into Molecular Structure

2H NMR studies of glycerol dynamics in protein matrices

Dynamics in molecular and molecular-ionic crystals: A combined experimental and molecular simulation study of reorientational motions in benzene, pyridinium iodide, and pyridinium nitrate

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