Helically Annelated and Cross-Conjugated -Oligothiophenes: A Fourier Transform Raman Spectroscopic and Quantum Chemic
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- 作者：Reyes Malavé ; Osuna ; Rocí ; o Ponce Ortiz ; Ví ; ctor Herná ; ndez ; Juan Teodomiro Ló ; pez Navarrete ; Makoto Miyasaka ; Suchada Rajca ; Andrzej Rajca ; Rainer Glaser
- 刊名：Journal of Physical Chemistry C
- 出版年：2007
- 出版时间：March 29, 2007
- 年：2007
- 卷：111
- 期：12
- 页码：4854 - 4860
- 全文大小：527K
- 年卷期：v.111,no.12(March 29, 2007)
- ISSN：1932-7455
文摘
This article describes Fourier transform Raman/infrared spectroscopic studies to determine the conjugationalproperties of novel 
le">-oligothiophenes, in which thiophene rings are helically annelated, forming a cross-conjugated 
-system. These helicenes may be viewed as fragments of the unprecedented carbon-sulfur (C2S)nhelix, having a sulfur-rich molecular periphery. The B3LYP/6-31G** vibrational analysis of the experimentalspectroscopic data for le">-oligothiophenes with three, seven, and eleven thiophene rings indicates selectiveenhancement of a limited number of Raman scatterings. In particular, the enhancement of the Raman-activeskeletal 
(C=C) stretching modes in the 1400-1300-cm-1 region is related to the occurrence of a vibroniccoupling between the highest-occupied molecular orbital and lowest-unoccupied molecular orbital frontiermolecular orbitals. Decreased dispersion of enhanced Raman scatterings and greatly increased near degeneracyof the highest occupied MOs with the increasing number of annelated thiophene rings suggest significantelectron localization in le">-oligothiophenes, similar to that in cross-conjugated -systems.
le">-oligothiophenes, in which thiophene rings are helically annelated, forming a cross-conjugated -system. These helicenes may be viewed as fragments of the unprecedented carbon-sulfur (C2S)nhelix, having a sulfur-rich molecular periphery. The B3LYP/6-31G** vibrational analysis of the experimentalspectroscopic data for le">-oligothiophenes with three, seven, and eleven thiophene rings indicates selectiveenhancement of a limited number of Raman scatterings. In particular, the enhancement of the Raman-activeskeletal (C=C) stretching modes in the 1400-1300-cm-1 region is related to the occurrence of a vibroniccoupling between the highest-occupied molecular orbital and lowest-unoccupied molecular orbital frontiermolecular orbitals. Decreased dispersion of enhanced Raman scatterings and greatly increased near degeneracyof the highest occupied MOs with the increasing number of annelated thiophene rings suggest significantelectron localization in le">-oligothiophenes, similar to that in cross-conjugated -systems.