Solvatochromic behaviour of new donor-acceptor oligothiophenes

Oligothiophene derivatives play a central role in the formulation of materials used in devices in the field of organic electronics. In this work we report the results of the study of UV-Vis absorption and fluorescence spectra, in several solvents, of a series of oligothiophenes recently synthesized in our laboratory. The studied oligothiophenes present different structures due to several factors: the Donor-Acceptor (D-A) or Acceptor-Donor-Acceptor (A-D-A) architecture; the number of thiophene rings in the backbone (ranging from three to eight); the number and position of solubilizing octyl chains in the backbone, and the type of acceptor moieties (from Knoevenagel condensation either with ethyl cyanoacetate or 3-ethylrhodanine). Since solvents with different polarities were adopted, we provide a detailed analysis on the observed positive and negative solvatochromism effects depending on the symmetry of the oligomers, the lengths of the backbones and the kind of acceptors adopted. Moreover, an electrochemical synthesis of a new donor-acceptor oligothiophene (which can be assumed as a model compound) by anodic dimerization is reported, along with the voltammetric analysis of the obtained product.