Tetrahedral Oligothiophenes; Synthesis, X-ray Analysis, and Optoelectronic Properties of Highly Symmetrical, 3D-Branched Oligothiophenes

Tetrakis(bithienyl)methane and tetrakis(terthienyl)methane have been synthesized from tetrakis(2-thienyl)methane by use of Suzuki-Miyaura coupling as a key reaction. Their trimethylsilyl (TMS) derivatives are also synthesized, X-ray analysis reveals that each oliaothiophene moiety tends to adopt anti-conformations and show,v relatively small torsion angles between the adjacent thiophene rings. While the longest absorption maxima of these tetrakis(oligothienyl)methanes exhibit only a slight bathochromic shift compared to the corresponding linear oligothiophene derivative, tetrakis(bithienyl)methane and its TMS derivative exhibit an appreciable red-shift in their fluorescence spectra. The intramolecular interaction between thienyl groups of tetrakis(2-thienyl)methane is supported by DFT calculation.