Molecular motion studied by NMR powder spectra. II. Experimental results for solid P4 and solid Fe(CO)5

Spiess, Hans Wolfgang; Grosescu, R.; Haeberlen, H.

doi:10.1016/0301-0104(74)85063-9

Cited by 119 publications

(53 citation statements)

References 15 publications

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“…The structure of the γ phase was determined to be monoclinic but close to orthorhombic [9]. The P 4 tetrahedra in both the alpha and beta structures show librational disorder 5 while the arrangement in the γ phase is virtually static [9]. Both of the low temperature transitions were found to be sluggish.…”

Section: Introductionmentioning

confidence: 96%

“…This study gave a transition temperature of approximately -80 o C at ambient pressure. An NMR study of wP found that cooling at ambient pressure to -165 o C resulted in a transformation to the γ phase [5]. On heating, a γ phase wP sample was found to transform to the β phase at -115 o C and then to the α phase at -77 o C. An x-ray study by Simon et al (1987) [6] found the β to α transition to be at -76.4 o C. A later study by Simon et al (1997) [7] found the beta to α transition occurred at -76.5 o C and the γ to beta transition occurred at -175 o C using differential thermal analysis and, from x-ray diffraction results, the α to β transition occurred at about -80 o C and the γ to β transition occurred at nearly -105 o C. A Raman study [8] found the β to α transition to occur at -78 o C and the γ to β transition to transpire at -183°C.…”

Section: Introductionmentioning

confidence: 99%

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Compressibility of cubic white, orthorhombic black, rhombohedral black, and simple cubic black phosphorus

Clark

Zaug

2010

Phys. Rev. B

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The effect of pressure on the crystal structure of white phosphorus has been studied up to 22.4 GPa. The α phase was found to transform into the α' phase at 0.87 ± 0.04 GPa with a volume change of 0.1 ± 0.3 cc/mol. A fit of a second order BirchMurnaghan equation to the data gave Vo = 16.94 ± 0.08 cc/mol and K o = 6.7 ± 0.5 GPa for the α phase and Vo = 16.4 ± 0.1 cc/mol and K o = 9.1 ± 0.3 GPa for the α' phase. The α' phase was found to transform to the A17 phase of black phosphorus at 2.68 ± 0.34 GPa and then with increasing pressure to the A7 and then simple cubic phase of black phosphorus. A fit of a second order Birch-Murnaghan equation to our data combined with previous measurements gave Vo = 11.43 ± 0.05 cc/mol and K o = 34.7 ± 0.5 GPa for the A17 phase, Vo = 9.62 ± 0.01 cc/mol and K o = 65.0 ± 0.6 GPa for the A7 phase and , Vo = 9.23 ± 0.01 cc/mol and K o = 72.5 ± 0.3 GPa for the simple cubic phase. PACS numbers:Phase transitions, crystallographic aspects of, 61.50.KsHigh-pressure effects, structural properties of materials, 81.40.Vw X-ray diffraction in crystal structure, 61.05.cp

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Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Compressibility of cubic white, orthorhombic black, rhombohedral black, and simple cubic black phosphorus

Clark

Zaug

2010

Phys. Rev. B

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“…Recent advances in solid state NMR techniques [3] have made available high resolution lineshapes for chemical shielding, and thus the possibility for much more detailed analysis of molecular motions in the solid state. Early studies of this type were made in cases for which the motion is of sufficiently high symmetry to reduce the powder lineshape to a single sharp line [4,5,7]. In such cases it is possible to distinguish.…”

Section: Introductionmentioning

confidence: 99%

NMR study of molecular reorientation under fivefold symmetry - solid permethylferrocene

Wemmer¹,

Ruben²,

Pines³

1981

J. Am. Chem. Soc.

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The ring reorientation in permethylferrocene has been studied using high resolution solid state 13 c NMR. The constraints which symmetry places upon the number and types of motional parameters which may be determined from the NMR spectrum are discussed. From comparison of the experimental lineshapes in the slow reorientation temperatures range with theoretical models for random rotations and symmetry related jumps, it is concluded that the reorientation occurs as jumps between symmetry related orientations with jumps of 2-n/5 highly favored over 4rr/5. The activation energy derived for the jump process is 13.5 kjoules/mole.

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“…The 13 C NMR spectrum of 13 C labeled Fe(CO) 5 exhibits only a single peak at all accessibly measured solution temperatures, indicating that 13 C nuclei shift between axial and equatorial positions faster than NMR spectroscopy is able to distinguish these two chemical environments (2)(3)(4). Careful analysis of IR, Raman, and NMR spectra of Fe(CO) 5 and various derivatives suggests that the exchange process possesses a low barrier and occurs on a time-scale of picoseconds (4)(5)(6). Nevertheless, the dynamics in solution have not been quantified.…”

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confidence: 98%

Determining Transition-State Geometries in Liquids Using 2D-IR

Cahoon

Sawyer

Schlegel

et al. 2008

Science

169

229

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Here, we demonstrate that ultrafast two dimensional infrared (2D-IR) spectroscopy provides evidence for the transition state involved in a simple thermal chemical reaction, the fluxionality of Fe(CO) 5 .Fluxionality refers to the rearrangement of a molecule between chemically indistinguishable structures.These reactions produce no net change in molecular structure, yet they are important for understanding the basic chemical behavior and reactivity of molecules in solution.Department of Chemistry, University of California, Berkeley, California 94720, and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 * These authors contributed equally and are listed alphabetically † corresponding author email address: cbharris@berkeley.edu 2 Fe(CO) 5 , an organometallic complex with five CO ligands arranged in a trigonal bipyramidal geometry, is a textbook example for fluxionality. In the late 1950s, nuclear magnetic resonance (NMR) spectroscopy revealed that this molecule rapidly exchanges its CO ligands between axial and equatorial sites. The 13 C NMR spectrum of 13 C labeled Fe(CO) 5 exhibits only a single peak at all accessibly measured solution temperatures, indicating that 13 C nuclei shift between axial and equatorial positions faster than NMR spectroscopy is able to distinguish these two chemical environments (2)(3)(4). Careful analysis of IR, Raman, and NMR spectra of Fe(CO) 5 and various derivatives suggests that the exchange process possesses a low barrier and occurs on a time-scale of picoseconds (4)(5)(6). Nevertheless, the dynamics in solution have not been quantified.From a general perspective, fluxional processes are simple chemical reactions in which a molecule briefly rearranges to a new symmetry and geometry as it crosses a transition state and then returns to its original geometry as it completes the reaction. We show for Fe(CO) 5 that during this process energy is exchanged between the vibrational modes of the reactive ligands. Quantification of this energy exchange provides direct information on the time-scale, transition state, and consequently, mechanism of the reaction.2D-IR spectroscopy has recently received much attention for its ability to monitor thermal reactions and chemical exchange on the femtosecond and picosecond time-scales. Conventionally, ultrafast timing of chemical reactions is achieved by photoinitiating the reactions with a short, intense laser pulse which electronically excites the molecules and typically leaves them with significant excess energy (1). In comparison, 2D-IR spectroscopy only requires vibrational excitation with an ultrafast IR laser pulse and allows the investigation of an entirely different class of thermally activated reactions in liquids at or close to equilibrium. Although similar to one-dimensional IR-pump, IR-probe experiments (1D-IR), 2D-IR spectroscopy separates the contributions to the 1D-IR spectrum into two frequency dimensions, which provides information on the correlations, anharmonicities, and exchange dynamics...

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Molecular motion studied by NMR powder spectra. II. Experimental results for solid P4 and solid Fe(CO)5

Cited by 119 publications

References 15 publications

Compressibility of cubic white, orthorhombic black, rhombohedral black, and simple cubic black phosphorus

Compressibility of cubic white, orthorhombic black, rhombohedral black, and simple cubic black phosphorus

NMR study of molecular reorientation under fivefold symmetry - solid permethylferrocene

Determining Transition-State Geometries in Liquids Using 2D-IR

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