Dependencies of the Raman spectra of p-oligophenyls on the chain length and the excitation wavelength

✍ Scribed by Hirofumi Ohtsuka; Yukio Furukawa; Mitsuo Tasumi

• Publisher: Elsevier Science
• Year: 1993
• Tongue: English
• Weight: 495 KB
• Volume: 49
• Category: Article
• ISSN: 1386-1425
• DOI: 10.1016/0584-8539(93)80097-t

✦ Synopsis

Ah&act

-The 1064nm excited Raman spectra of p-terphenyl, pquaterphenyl, p-quinquephenyl and psexiphenyl have been observed and compared with the 514.5 nm excited spectra. Dependencies of intensities of some major bands on the chain length and the excitation wavelength are discussed in terms of the preresonant Raman effect. A method for estimating the chain length from relative intensities is proposed. MOLECULAR structures and spectra of p-oligophenyls (Fig. l), a series of compounds starting at biphenyl, have received considerable attention over decades, because they are thought to provide useful information for the work aimed at establishing a general view on n-electron conjugation. Interest in this subject has increased [l-8] since poly(pphenylene) was found to show high electrical conductivities upon doping [9].

We have observed 1064 nm excited Fourier transform (FlJ Raman spectra from pterphenyl, p-quaterphenyl, p-quinquephenyl and p-sexiphenyl. The resultant spectra depend greatly on the chain length in accordance with the result of a previous study using 676.4 nm excitation [2]. In the present paper, we will show that dependencies of the relative intensities of some Raman bands on the chain length, if examined in detail, seem to clarify origins of the relevant bands. Information obtainable from comparisons of the Raman spectra observed with 1064 and 514.5 nm excitations will also be examined.

EXPERIMENTAL

Samples of p-terphenyl, p-quaterphenyl, p-quinquephenyl and p-sexiphenyl were purchased from the Tokyo Chemical Industry Co., and used without further purification. The powder samples sealed in a glass capillary tube (inner diameter, 1 mm) were employed for Raman measurements.