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

Abstract

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.

Direct Mechanocatalysis: Palladium as Milling Media and Catalyst in the Mechanochemical Suzuki Polymerization

“…The materials were also investigated via Raman spectroscopy (Figure C and Figure S3) where characteristic bands were observed at 1220 cm −1 (ν intra‐ring (C−C)), 1280 cm −1 (ν inter‐ring (C−C)), and 1600 cm −1 (δ in‐plane (C−H)) . Fitting the spectral peaks by a Lorentzian function and comparing the intensities of the peaks at 1220 cm −1 and 1280 cm −1 validated qualitatively the high degree of polymerization as calculated from FTIR. However, quantification was not possible with this technique, since the polymers were already too long (for further information see Section 4 in the Supporting Information) …”

Impact of Low‐Frequency Vibrations on Charge Transport in High‐Mobility Organic Semiconductors

“…Very recently, the comparative study of LF Raman spectra of oligophenyls ( n = 1–6) was reported in ref. . These spectra are presented in Figure b and show that the lowest‐frequency mode redshifts with n as in oligoacenes.…”

“…, and for oligophenyls from ref. . For tetracene and pentacene, the spectra corresponding to the two stable crystal structures (LT and HT phases, see Section 4.2) are shown.…”

Order–disorder transition in p-oligophenyls

“…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.…”

“…The intensity ratio of these two modes are also always used to estimate the molecular conjugation. 39,50,55 However, due to the drastic splits of these peaks, it becomes more difficult to distinguish the peaks. Here we choose two peaks located at around 1600 cm −1 with the strongest intensities, then calculate the intensity ratios of the five materials, the temperature dependent intensity ratios between the lower energy peaks and the higher energy peaks of POPs are presented in Figs.…”