Low-temperature carbon-13 magnetic resonance in solids.  6.  Methine carbons

Facelli, Julio C.; Orendt, Anita M.; Solum, Mark S.; Depke, Gisbert; Grant, David M.; Michl, Josef

doi:10.1021/ja00275a005

Cited by 33 publications

(19 citation statements)

References 1 publication

(8 reference statements)

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“…It is noted that bond contributions in the local bond frames become independent of the explicit molecular geometry, making a comparison in a series of molecules possible.11,28 This analysis has been used to analyze the 13C shielding tensors in methine and methyl carbons. 27,28 Semiempirical theories of chemical shielding are in general less successful than ab initio ones,41 but their simplicity and low computational cost make them appropriate for larger molecular systems for which current computational resources preclude the use of ab initio methods. In connection with the experimental work done in Utah, the very simple Pople model,55,56 using an MNDO wave function,57 has been used to rationalize the in-plane components of the 13C shielding tensors in pyrene.58…”

Section: Theoretical Methodsmentioning

confidence: 99%

Carbon-13 shielding tensors: experimental and theoretical determination

Facelli¹,

Grant²,

Michl³

1987

Acc. Chem. Res.

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Section: Theoretical Methodsmentioning

confidence: 99%

Carbon-13 shielding tensors: experimental and theoretical determination

Facelli¹,

Grant²,

Michl³

1987

Acc. Chem. Res.

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“…23 This is unlike most plastic crystalline phases which are frequently cubic. [25][26][27][28] The transition is a first order and associated with 5.4% increase in unit cell volume. [25][26][27][28] The transition is a first order and associated with 5.4% increase in unit cell volume.…”

Section: Introductionmentioning

confidence: 99%

What does pressure decide to cook with orientationally disordered plastic phase of cubane: An orientational glass or crystal?

Murugan

2005

The Journal of Chemical Physics

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The effect of pressure on the structure and reorientational motion of molecules in orientationally disordered (OD) crystalline phase of cubane has been investigated in detail using variable shape molecular simulations in constant-pressure constant-temperature ensemble. Complete orientational ordering occurs at a pressure of 1.0 GPa and the OD phase transforms to an orientationally ordered phase at this pressure. The transition is associated with a kink in the variation of structural parameters such as cell parameters, unit-cell volume, and interaction energy. This transition is also associated with an anomaly in specific heat. Above this transition pressure, the structural quantities display only smaller changes with further increase in pressure. The structure of high-pressure orientationally ordered (HPOO) phase has been characterized using radial distribution functions and orientational distribution function. From detailed analysis of the structure of HPOO phase we conclude that it is isostructural with low-temperature orientationally ordered phase. The OD phase has four times larger compressibility than the HPOO phase.

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“…Solid cubane undergoes a first‐order transition at 394 K from an orientationally ordered phase to a noncubic orientationally disordered (plastic) phase 4, 6–8. Although many studies have all shown evidence of this transition, the structure of the high‐temperature phase was not identified until recently.…”

Section: Introductionmentioning

confidence: 99%

Molecular interaction energies and optimal configuration of a cubane dimer

Николаев¹,

Verberck²,

Ionova³

2009

Int J of Quantum Chemistry

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ABSTRACT:We have studied the dependence of the binding energy of a cubane dimer on the mutual orientation of and the distance between the composing monomers employing the second-order Møller-Plesset perturbation scheme (MP2) with the ccpVDZ molecular basis set. We have found that the MP2 contribution from the molecular correlations is responsible for the bound state of the cubane dimer, whereas the Hartree-Fock contribution remains anti-bonding at all intermolecular distances. Starting with two molecules in the standard orientation and centers of mass at (0,0,0) and (0,0,d), respectively, the maximal binding energy is found at d ϭ 5.125 Å and one of the monomers rotated by 45°about the z-axis. This configuration implies that the hydrogen atoms belonging to different monomers tend to repel each other. The results are in agreement with experimental data on the optimal packing of cubane molecules in the solid state.

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Low-temperature carbon-13 magnetic resonance in solids. 6. Methine carbons

Cited by 33 publications

References 1 publication

Carbon-13 shielding tensors: experimental and theoretical determination

Carbon-13 shielding tensors: experimental and theoretical determination

What does pressure decide to cook with orientationally disordered plastic phase of cubane: An orientational glass or crystal?

Molecular interaction energies and optimal configuration of a cubane dimer

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