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FT Raman and DFT Study on a Series of All‐anti Oligothienoacenes End‐Capped with Triisopropylsilyl Groups |
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| Authors: | Reyes Malavé Osuna Víctor Hernández Prof. Dr. Juan T. López Navarrete Prof. Dr. Juan Aragó Pedro M. Viruela Prof. Dr. Enrique Ortí Prof. Dr. Yoshitake Suzuki Prof. Dr. Shigehiro Yamaguchi Prof. Dr. John T. Henssler Prof. Dr. Adam J. Matzger Prof. Dr. |
| Affiliation: | 1. Department of Physical Chemistry, University of Málaga, 29071 Málaga (Spain), Fax: (+34)?952‐132000;2. Instituto de Ciencia Molecular, Universidad de Valencia, P.O. Box 22085, 46071 Valencia (Spain), Fax: (+34)?963543274;3. Department of Chemistry, Graduate School of Science, Nagoya University, Furo, Chikusa, Nagoya, 464‐8602 (Japan);4. Department of Chemistry and the Macromolecular Science and Engineering Program, University of Michigan, 930 North University, Ann Arbor, Michigan 48109‐1055 (USA) |
| Abstract: | Herein, we study the π‐conjugational properties of a homologous series of all‐anti oligothienoacenes containing four to eight fused thiophene rings by means of FT Raman spectroscopy and DFT calculations. The theoretical analysis of the spectroscopic data provides evidence that selective enhancement of a very limited number of Raman scatterings is related to the occurrence in these oligothienoacenes of strong vibronic coupling between collective ν(C?C) stretching modes in the 1600–1300 cm?1 region and the HOMO/LUMO frontier orbitals (HOMO=highest occupied molecular orbital; LUMO=lowest unoccupied molecular orbital). The correlation of the Raman spectroscopic data and theoretical results for these all‐anti oligothienoacenes with those previously collected for a number of all‐syn oligothienohelicenes gives further support to the expectation that cross‐conjugation is dominant in heterohelicenes. Fully planar all‐anti oligothienoacenes display linear π conjugation which seemingly does not reach saturation with increasing number of annulated thiophene rings in the oligomeric chain at least up to the octamer. |
| Keywords: | acenes computational chemistry conjugation density functional calculations Raman spectroscopy |