Helically annelated and cross-conjugated β-oligothiophenes: A fourier transform Raman spectroscopic and quantum chemical density functional theory study

Reyes Malavé Osuna, Rocío Ponce Ortiz, Víctor Hernández, Juan Teodomiro López Navarrete, Makoto Miyasaka, Suchada Rajca, Andrzej Rajca, Rainer Glaser

Research output: Contribution to journalArticle

14 Scopus citations

Abstract

This article describes Fourier transform Raman/infrared spectroscopic studies to determine the conjugational properties of novel β- oligothiophenes, in which- thiophene rings are helically annelated, forming a cross-conjugated π-system. These helicenes may be viewed as fragments of the unprecedented carbon-sulfur (C2S)n helix, having a sulfur-rich molecular periphery. The B3LYP/6-31G** vibrational analysis of the experimental spectroscopic data for β-oligothiophenes with three, seven, and eleven thiophene rings indicates selective enhancement of a limited number of Raman scatterings. In particular, the enhancement of the Raman-active skeletal v(C=C) stretching modes in the 1400-1300-cm-1 region is related to the occurrence of a vibronic coupling between the highest-occupied molecular orbital and lowest-unoccupied molecular orbital frontier molecular orbitals. Decreased dispersion of enhanced Raman scatterings and greatly increased near degeneracy of the highest occupied MOs with the increasing number of annelated thiophene rings suggest significant electron localization in β-oligothiophenes, similar to that in cross-conjugated π-systems.

Original languageEnglish (US)
Pages (from-to)4854-4860
Number of pages7
JournalJournal of Physical Chemistry C
Volume111
Issue number12
DOIs
StatePublished - Mar 29 2007

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

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