Albrecht theory and anharmonic coupling in polyphenyl Raman spectra

Heimel, Georg; Somitsch, D.; Knöll, P.; Zojer, Egbert

doi:10.1016/s0379-6779(03)00374-6

Cited by 9 publications

(8 citation statements)

References 24 publications

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“…The C-H in-plane bending modes and the interring C-C stretching modes located at around 1220 and 1280 cm −1 are common indicators to identify the molecular conjugations at ambient condition (chain length and planarity). 39,[50][51][52][53][54] The energy separation of these two modes increases with increasing phenyl ring number in one molecule. And the intensity ratio of the POPs monotonously declines, but the pace of the declines slows, it almost converges to zero for the infinite long polymer (see Fig.…”

Section: Methodsmentioning

confidence: 99%

“…The intensity ratio is always used to indicate the molecular conjugation and the structural transition. [39][40][41][42][50][51][52][53][54] However, all these two peaks exhibit severe splits below the transition temperature, it makes the selects of the two peaks more difficult. Here, we choose two peaks with strongest intensities at around 1220 and 1280 cm −1 , respectively, and the results are compared with the P2P, P3P, and P4P.…”

Section: Methodsmentioning

confidence: 99%

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Order–disorder transition in p-oligophenyls

Zhang

Wang

Chen

2019

Phys. Chem. Chem. Phys.

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Poly(para-phenylene) has been recognized as one important family of conducting polymers upon doping with donors or acceptors. This system possesses a chain-like structure with infinite benzene rings linked with the single C-C bond. Oligophenyls as models of poly(para-phenylene) with short chains in the para position were found to exhibit superconductivity at transition temperatures ranging from 3 K to 123 K upon dopant. Structural studies have revealed that there exist the orderdisorder transitions in many p-oligophenyls with almost doubled lattice constants in the b and c directions at low temperatures, seemingly supporting the formation of the charge-density-wave order. Such a transition is of relevance to the understanding of the emergence of novel quantum functionality where unconventional polaronic interactions are relevant for the new emerging theory of superconductivity in this system. However, the accurate temperatures for the order-disorder transitions amongst these p-oligophenyls are still needed to be determined. The chain length effects on the order-disorder transitions in this system remain unknown. Here we report the systematic investigation of the evolution of vibrational properties of the crystalline p-oligophenyls over a wide temperature range. The order-disorder transition is identified by three indicators, the lowest energy peak together with the intensity ratios between the 1280 cm −1 and 1220 cm −1 modes and between the two modes at around 1600 cm −1 . A phase diagram of the order-disorder transition temperature as well as the melting curve for p-oligophenyls is thus established. The former is found to increase with the chain length and saturates at around 350 K for poly(para-phenylene).

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Order–disorder transition in p-oligophenyls

Zhang

Wang

Chen

2019

Phys. Chem. Chem. Phys.

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“…Consequently, it is often used to estimate the length of PPP materials. [33][34][35] The ratio of the intensities of these two peaks is also an indicator of the inter-ring torsion angle. [36][37][38][39] In PPP materials, all the molecular orbitals can be divided into delocalized orbitals and localized orbitals.…”

Section: CM −1 Mode and 1280 Cm −1 Modementioning

confidence: 99%

“…Therefore, these two peaks have also been suggested to estimate the conjugation of the molecules. 34,35,38,39 The identification of the chain length effects on POPs will be more clear if the basic starting compound benzene is included.…”

Section: Introductionmentioning

confidence: 99%

“…32 For POPs with a long C-C chain length, the ratio of the integral intensity of the 1280 cm −1 and 1220 cm −1 modes in the Raman spectra has often been used to distinguish the chain lengths between different compounds. [33][34][35] It thus serves as an indicator of the planarization of molecules at ambient conditions 36,37 or high pressures. 38,39 Meanwhile, the features of the two peaks at around 1600 cm −1 is also particular.…”

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confidence: 99%

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Chain length effects of p-oligophenyls with comparison of benzene by Raman scattering

Zhang

Chen

2018

AIP Advances

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Raman scattering measurements are performed on benzene and a number of p-oligophenyls including biphenyl, p-terphenyl, p-quaterphenyl, p-quinquephenyl, and p-sexiphenyl at ambient conditions. The vibrational modes of the intra-and intermolecular terms in these materials are analyzed and compared. Chain length effects on the vibrational properties are examined for the C-H in-plane bending mode and the inter-ring C-C stretching mode at around 1200 cm −1 and 1280 cm −1 , respectively, and the C-C stretching modes at around 1600 cm −1 . The complex and fluctuating properties of these modes result in an imprecise estimation of the chain length of these molecules. Meanwhile, the obtained ratio of the intensities of the 1200 cm −1 mode and 1280 cm −1 mode is sensitive to the applied lasers. A librational motion mode with the lowest energy is found to have a monotonous change with the increase in the chain length. This mode is simply relevant to the c axis of the unit cell. Such an obvious trend makes it a better indicator for determining the chain length effects on the physical and chemical properties in these molecules.

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Fermi resonance: A new way to investigate the planarization of p-quaterphenyl under high pressure

Han

Song

et al. 2020

Chemical Physics Letters

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Albrecht theory and anharmonic coupling in polyphenyl Raman spectra

Cited by 9 publications

References 24 publications

Order–disorder transition in p-oligophenyls

Order–disorder transition in p-oligophenyls

Chain length effects of p-oligophenyls with comparison of benzene by Raman scattering

Fermi resonance: A new way to investigate the planarization of p-quaterphenyl under high pressure

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