Triplet Energy Studies of Thiophene and para-Phenylene Based Oligomers

Leandro A. Estrada, Victor A. Montes, Grigory Zyryanov, and Pavel Anzenbacher, Jr.*
Department of Chemistry and Center for Photochemical Sciences, Bowling Green State University, Bowling Green, Ohio 43403
J. Phys. Chem. B, 2007, 111 (25), pp 6983–6986
DOI: 10.1021/jp0726945
Publication Date (Web): May 25, 2007
Copyright © 2007 American Chemical Society
*

 To whom correspondence should be addressed. E-mail:  pavel@bgsu.edu.

Abstract

Abstract Image

A series of conjugated materials based on oligomers of the para-phenylene type and oligothiophenes was prepared, and their phosphorescence spectra were recorded at 77 K using a pulsed flash-lamp as a light source and gated detection. The triplet energies of the oligomers were estimated and correlated with their chemical structure. It was found that simple changes in the building block sequence in the thiophene-containing oligomers allowed for tuning the triplet energy from 1.86 to 2.35 eV (530−670 nm). Hypsochromic shifts and little variation of the triplet energy were obtained with increasing length of the π-system for thiophene end-capped oligomers, contrary to the usual behavior of unsubstituted oligomers. The experimental results were supported with theoretical computations from density functional theory (B3LYP/6-31G*) calculations, which indicated that changes in the geometry and delocalization of the triplet excited state account for the trends in the triplet energy evolution.

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History

  • Published In Issue June 28, 2007
  • Received April 5, 2007
    Revised May 3, 2007

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