Photophysical Study of Twop-Phenylenevinylene Oligomers End-Capped with Triphenylamine or Cyanoacetate Groups.

Abstract

The photophysical properties of two p‐phenylenevinylene trimer end‐capped with triphenylamine or cyanoacetate groups were investigated with special attention to the different donor‐acceptor character of the terminal units, relatively to a same central phenylenevinylene trimer. It is shown that these conjugated small molecules constitute a quite useful model system to understand how the end‐capped groups couple to the central molecular unit with respect to energy and/or electron transfer. The study of these two compounds in solution showed that after photoexcitation, the conformational relaxation leads to an increase in the conjugated backbone planarization. A more pronounced intramolecular charge transfer in the excited state of the molecule with two alkyl cyanoacetate groups as electron‐withdrawing ends was also found. The molecular structures of the two compounds are especially advantageous for electronic applications such as organic photovoltaics, for example, due to their narrow optical band gaps that potentially lead to a more efficient photon harvesting in the organic devices fabricated with these compounds.