Aromatic Symmetric Cyclotrimers and Poly(arylenevinylene)s with Branched Aromatic Substituents in Vinylene Groups. Synthesis and Optical Properties

Abstract

New poly(arylenevinylene)s were realized by Ni0-catalyzed polymerization of aromatic dibromides, containing vinylene groups substituted completely with branched oligophenylenes. The monomers were synthesized by acylation of 1,3,5-triphenylbenzene or 1,3,5-tri-(diphenylyl)benzene with 4-bromobenzoyl chloride followed by the McMurry homocondensation in the presence of TiCl4 and Zn. Model cyclotrimers with 1,3,5-trisubstituted benzene core were synthesized and characterized. Their molar extinction coefficients and luminescence quantum yields were in the ranges (0.5–1.5)·105 M–1· cm–1 and 29–72%, respectively. The highest quantum yield 92% promising for further photophysical investigation was found for the cyclotrimer with tolan as substituent. The quantum yield of the cyclotrimers depended on both the symmetry of molecules and the amount of benzene rings in the ambience. The incorporation of the substituents of three-dimensional structure instead of benzene rings led the polymers to become rather highly emissive with fluorescence quantum yields of 22–23% in comparison to the value of 1% of polymer with benzene rings.