Structure and chain polarization of long polyynes investigated with infrared and Raman spectroscopy1. (27th May 2013)

• Record Type: Journal Article
• Authors: Agarwal, N. R.; Lucotti, A.; Fazzi, D.; Tommasini, M.; Castiglioni, C.; Chalifoux, W.A.; Tykwinski, R. R.
• Other Names: Kiefer Johannes guestEditor.; Radi Peter guestEditor.; Giorgini Maria Grazia guestEditor.
• Is Part Of: Journal of Raman spectroscopy. Volume 44:Number 10(2013:Oct.)
• Page Start: 1398
• Page End: 1410
• Publication Date: 2013-05-27
• Subjects: polyynes -- sp‐carbon chains -- phonons -- Raman and IR spectroscopy -- density functional theory calculations; Raman spectroscopy -- Periodicals; 535.846
• DOI: 10.1002/jrs.4300
• Languages: English
• ISSNs: 0377-0486

Abstract

Abstract : Symmetrically and unsymmetrically endcapped polyynes (triisopropylsilyl – TIPS – and super trityl endcapping groups) have been studied with density functional theory calculations and Raman and infrared spectroscopy. This spectroscopic investigation provides general guidelines for studying the vibrational and structural features of sp‐carbon‐based materials, which nowadays are at the center of growing interest for the potential applications of nanostructured carbon materials in molecular electronics. On the basis of the description of CC stretching modes of polyynes in terms of longitudinal optical phonons of the parent infinite sp‐carbon chain, we have carried out the complete assignment of the observed infrared and Raman features in the 2300–1900 cm −1 range, for chain lengths in the range 4–20 triple bonds. This allows demonstration of polarization effects induced by an unsymmetric structure and deviations from chain linearity in long polyynes. Copyright © 2013 John Wiley & Sons, Ltd. Abstract : Using vibrational spectroscopy and density functional theory calculations, long symmetrically capped polyynes have been studied as a function of increasing chain length for phonon dispersions. Unsymmetrically capped polyynes have been also studied as a comparison. Raman and infrared data demonstrate polarization and structural effects for these series of long polyyne chains.