Transitions de phase structurales dans les polyphényles. IX. Affinements des structures du p-terphényle hydrogéné à 200 K (diffraction des rayons X) et du biphényle deutéré à 40 K (diffraction des neutrons)

Baudour, J. L.; Toupet, L.; Délugeard, Y.; Ghémid, S.

doi:10.1107/s0108270186092843

Cited by 34 publications

(24 citation statements)

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“…Biphenyl's conformation is governed by a double-well potential with a barrier height of 3 kJ mol-', which is to be compared with the experimental results of Baudour, Cailleau & Yelon (1977), demonstrating that the libration of the central phenyl ring in p-terphenyl is governed by a double-well potential with a barrier height of 2.5 kJ mol-1 We believe that this suffices to show that a real difference in behaviour between pterphenyl and biphenyl is very unlikely, in contrast to the opinion of Baudour et al (1986). For example, at 110 K a value of L22 = 46 deg 2 is observed to be compared with values of about 3 deg 2 for L11 and L33 (Charbonneau & D61ugeard, 1976).…”

Section: Biphenyl In the High-temperature Solid Statementioning

confidence: 99%

“…For example, at 110 K a value of L22 = 46 deg 2 is observed to be compared with values of about 3 deg 2 for L11 and L33 (Charbonneau & D61ugeard, 1976). Table 2 gives root-mean-square values for L22 as a function of the temperature, as summarized by Baudour et al (1986). The r.m.s, values follow a standard pattern, i.e.…”

Section: Biphenyl In the High-temperature Solid Statementioning

confidence: 99%

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Solids modelled by crystal field ab initio methods. 5. The phase transitions in biphenyl from a molecular point of view

Lenstra¹,

Alsenoy²,

Verhulst³

et al. 1994

Acta Crystallogr Sect B

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Section: Biphenyl In the High-temperature Solid Statementioning

confidence: 99%

Section: Biphenyl In the High-temperature Solid Statementioning

confidence: 99%

Solids modelled by crystal field ab initio methods. 5. The phase transitions in biphenyl from a molecular point of view

Lenstra¹,

Alsenoy²,

Verhulst³

et al. 1994

Acta Crystallogr Sect B

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“…The alternative is a single-well harmonic potential leading classically to the prediction (42) ~ T and, from the slope of (~£ vs. T, to an estimate of the frequency v (or the wave number //) of the harmonic oscillator. The debate has settled in favor of this latter alternative, but despite the fact that an (approximate) linearity between L22 and T has been noted explicitly [10], no one appears to have used the L2z(T ) data to propose a value for /'.…”

Section: Introductionmentioning

confidence: 99%

Dynamics in molecular crystals: An application of proton NMR to selectively protonated biphenyl. Do the rings flip together or independently?

et al. 2003

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The synthesis of a specific isotopomer, C6D4H(ortho)-H(ortho)D4C6 of biphenyl is reported. The intramolecular dipolar coupling of the protons leads to a well-resolved single-crystal proton nuclear magnetic resonance (NMR) spectrum and allows one to study the dynamics of the phenyl rings in a unique way. At room temperature and above, the most conspicuous dynamical mode consists of 180° ring flips. The present data together with previous measurements of the total flip rate allow us to conclude that the rings flip almost exclusively independently of each other. Between the incommensurate (IC) phase transition of biphenyl at 38 K andT=250 K, the prominent namical mode consists of oscillatory twists ϕ(t) of the two rings. The data allow us to infer the mean square, (φ2), of these twists. (φ2) is found to grow linearly withT for 50

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“…From the similarity of the p-terphenyl and pquaterphenyl structures, we can take 2q~ = 13.3 °, the value obtained by resolving the disorder in the hightemperature phase of p-terphenyl (Baudour et al, 1977(Baudour et al, , 1986). Thus we obtain the torsion angle 0o between two phenyl rings at equilibrium, when intramolecular interactions only are considered: 0o = 46.55 ~.…”

Section: \ Ool Oomentioning

confidence: 99%

Structural phase transition in polyphenyls. X. Potential barrier heights in crystalline polyphenyls and in gaseous biphenyl determined uniquely from diffraction data

Baudour¹

1991

Acta Crystallogr Sect B

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The analysis from X-ray or neutron diffraction data, of the librational motion around the long molecular axis of the p-terphenyl central ring permits resolution of its disorder: the phenyl rotation angle on either side of the average molecular plane is ¢ = _+ 13.3 c. This disorder is associated with a double-well potential between two twisted conformations, and the overall libration on each site, at the bottoms of the double well, has the mean-square amplitude (02) = 52.5 deg 2 at room temperature. The analysis also permits separation in (02) of the mean-square amplitude of the torsional g mode (0~) = 35 deg 2 from that of the external mode (0~) = 17.5deg 2. Thus it becomes possible to scale the parameters of a simple model describing inter-and intramolecular interactions in the whole family of polyphenyls. It is shown that the intramolecular potential between two adjacent phenyl rings cannot be described by a simple sinusoidal function but exhibits a steeper gradient near the planar conformation. This double potential well model accounts for disorder and libration in crystalline p-terphenyl and p-quaterphenyl. an estimation of potential barrier heights: V = 4.57 kJ mol-1 in p-terphenyl and 7.91 kJ mol-' in p-quaterphenyl in good agreement with NMR results. It agrees with the displacive nature of the biphenyl transition by giving in this case a barrier height, V = 1.25 kJ mol-~, significantly less than the thermal energy kT and a singly peaked probability density function associated with a large libration amplitude as observed experimentally. Combined with the estimation of librational amplitude from diffraction data it predicts a large increase of intermolecular interactions in biphenyl at low temperature and gives an estimation of the interactions involved in the low-temperature incommensurate phase of biphenyl. Indirectly it is one of the very few experimental determinations of the potential-energy curve for gaseous biphenyl, giving V0 = 10"82kJmol ~ for the planar conformation in agreement with the results of gas-phase electron diffraction for deuterated biphenyl.

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Transitions de phase structurales dans les polyphényles. IX. Affinements des structures du p-terphényle hydrogéné à 200 K (diffraction des rayons X) et du biphényle deutéré à 40 K (diffraction des neutrons)

Cited by 34 publications

References 0 publications

Solids modelled by crystal field ab initio methods. 5. The phase transitions in biphenyl from a molecular point of view

Solids modelled by crystal field ab initio methods. 5. The phase transitions in biphenyl from a molecular point of view

Dynamics in molecular crystals: An application of proton NMR to selectively protonated biphenyl. Do the rings flip together or independently?

Structural phase transition in polyphenyls. X. Potential barrier heights in crystalline polyphenyls and in gaseous biphenyl determined uniquely from diffraction data

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