title: Synthesis, spectroscopic properties, and electropolymerization of azulene dyads.
abstract: Four azulene dyads have been synthesized and studied by spectroscopic and electrochemical methods. A triarylamine, a boron-dipyrromethene (BDP or BODIPY), a porphyrin, and an isoalloxazine moiety have been linked to an extended π electron system at the 2-position of azulene, leading to the dyads 1-4, respectively. For the synthesis of 1-4, first 2-(4-ethynyl-phenyl)azulene (EPA) was prepared, which was further reacted with the halogenated chromophores by Pd-catalyzed cross-coupling reactions. The dyads 1-4 exhibit strong absorption bands in the visible range, which are dominated by the absorption spectra of the individual subchromophores. Fluorometric studies of 2-4 revealed that after excitation of the subchromophoric unit attached to the parent azulene moiety, quenching mainly through energy transfer to azulene is effective, whereas possible charge-transfer interactions play only a minor role. Potentiodynamic oxidation of the dyads 1-4 leads to the formation of polymer films, which are deposited at the electrode. The polymer film derived from 1 was further characterized by spectroelectrochemistry. During positive doping of poly-1, a strong absorption band appears at 13,200 cm(-1), which is typical for triarylamine radical cations. This band is overlapping with a broad absorption band in the low-energy region that might be caused by charge-transfer interactions within the polymer.
authors.affiliation: FB 8, Organische Chemie, Universität Siegen, Adolf Reichwein Strasse 2, D-57068 Siegen, Germany. noell@chemie.uni-siegen.de
authors.forename: Gilbert
authors.initials: G
authors.lastname: Nöll
authors.forename: Jörg
authors.initials: J
authors.lastname: Daub
authors.forename: Michaela
authors.initials: M
authors.lastname: Lutz
authors.forename: Knut
authors.initials: K
authors.lastname: Rurack