# Optical Absorption and Emission Properties of End-capped Oligothienoacenes: A Joint Theoretical and Experimental Study

 Title: Optical Absorption and Emission Properties of End-capped Oligothienoacenes: A Joint Theoretical and Experimental Study Author: Aspuru-Guzik, Alan; Delgado, Carmen Ruiz; Ferrón, Cristina Capel; Osuna, Reyes Malavé; Hernández, Víctor; Navarrete, Juan T. López; Sanchez-Carrera, Roel Note: Order does not necessarily reflect citation order of authors. Citation: Sánchez-Carrera, Roel S., M. Carmen Ruiz Delgado, Cristina Capel Ferrón, Reyes Malavé Osuna, Victor Hernández, Juan T. López Navarrete, and Alán Aspuru-Guzik. 2010. Optical absorption and emission properties of end-capped oligothienoacenes: a joint theoretical and experimental study. Organic Electronics 11(10): 1701-1712. Full Text & Related Files: Optical_Absorption_and_Emission_Properties.pdf (1.398Mb; PDF) Abstract: The electron–vibration coupling in a family of silyl end-capped oligothienoacenes is investigated on the basis of a joint experimental and theoretical study using UV–vis absorption and emission spectroscopies and density functional theory calculations. Well-resolved vibronic progressions are found in the low-temperature absorption and emission profiles of these silyl-functionalized organic molecules. As the size of the oligomer lengthens a bathochromic shift is observed in the near-UV–vis range, indicative of the extension of the effective π-conjugation. The absorption and emission bands are practically mirror-symmetric. The combination of two normal modes with frequencies of $$\sim 1500 cm^{−1}$$ and $$\sim 500 cm^{−1}$$ determines the main vibronic progression in absorption and emission for all the series, although for larger oligomers (n = 6, 7, and 8) the presence of low-frequency normal modes ($$\sim100 cm^{−1}$$) is also evident. The spacing of the vibrational features is slightly larger in absorption than in emission; this agrees with the predicted shifting of the C−C stretching modes of the inner-most ring toward the high-frequency region as a result of the reversal of the single–double C−C pattern in the electronic excited-state. Our calculations indicate that the contributions of the end-capping groups to the total relaxation energy of the $$S_0 \rightarrow S_1$$ and $$S_1 \rightarrow S_0$$ transitions are almost negligible. This result suggest that the vibronic structure and to a large extent the spectral profiles of the silyl end-capped oligothienoacenes are mainly determined by their respective oligothienyl core. Published Version: http://dx.doi.org/10.1016/j.orgel.2010.07.001 Terms of Use: This article is made available under the terms and conditions applicable to Open Access Policy Articles, as set forth at http://nrs.harvard.edu/urn-3:HUL.InstRepos:dash.current.terms-of-use#OAP Citable link to this page: http://nrs.harvard.edu/urn-3:HUL.InstRepos:9637920

### This item appears in the following Collection(s)

• FAS Scholarly Articles [5133]
Peer reviewed scholarly articles from the Faculty of Arts and Sciences of Harvard University