Tripodal pyrene chromophores for semiconductor sensitization: new footprint design

Large footprint tripodal linkers for metal oxide nanoparticle sensitization, substituted with pyrene as the dye, and three COOR binding groups in para or meta position, were prepared to study the effect of the anchoring group position and of the footprint size on the sensitization processes. Two tripods based on tetraphenylsilane, (1-pyrenyl-4-ethynyl-phenyl)-tris(4-carbomethoxyphenyl-4-ethynyl-phenyl)silane, and (1-pyrenyl-4-ethynyl-phenyl)-tris(4-(4-methoxybenzyloxycarbonyl)phenyl-4-ethynyl-phenyl)silane, decomposed during hydrolysis, while the tetraphenyladamantane derivative, 1-(1-pyrenyl-4-ethynyl-phenyl)-3,5,7-(3-carbomethoxyphenyl-4-ethynyl-phenyl)adamantane, was chemically stable and was readily converted into the corresponding acid and bound to TiO2 films. The FT-IR-ATR spectrum of 1-(1-pyrenyl-p-ethynyl-phenyl)-3,5,7-(3-carboxyphenyl-4-ethynyl-phenyl)adamantane bound to TiO2 nanoparticles showed bands characteristic of carboxylate bidentate bonds. The UV–vis absorption and fluorescence emission in THF solution at room temperature were typical of pyrenes substituted with oligophenyleneethynylene linkers.