One of the most important research interests in the field of organic photovoltaic devices (OPVs) is the development of new materials which can serve as light-absorbing electron donors and hole-conducting (ptype) semiconductors. In this context, 1,3-polyazulenes were synthesized chemically and electrochemically. Their spectroscopic and electrochemical properties are compared with those of the 1,3-oligoazulenes Az 1 -Az 6 . The UV-vis spectra of the neutral azulenes Az 1 -Az 6 show a linear correlation between the lowest absorption maximum and the inverse chain length 1/n leading to a band gap of E g ) 1.90 eV for infinite chain length. Derived from this correlation the effective conjugation length of chemically synthesized polyazulene is only about 10. By an alternative approach, a band gap of E g ) 1.46 eV was determined. Depending on the applied potential the oligomers Az 2 -Az 6 undergo up to two reversible oxidation processes or further polymerization which results in the formation of polymer films at the electrode. The potentiodynamic oxidation of chemically synthesized polyazulene leads to electrocrystallization at the electrode, whereas films of polyazulenes are obtained directly upon oxidation of Az 1 -Az 6 . Chemically and electrochemically generated polyazulenes adsorbed on Pt show similar electrochemical behavior upon positive doping. The spectroelectrochemical investigations in combination with density functional theory (DFT) calculations lead to the conclusion that polyazulene can be oxidized up to a doping level of one charge per three or four azulene units. At this stage polarons or polaron pairs are formed (depending on the doping level) but not bipolarons. At higher doping levels the polymers start to decompose.

The bis(triarylamine) systems 1−5 were synthesized and investigated by spectroscopic and electrochemical methods. They all have an aromatic five-membered ring system in common as a central part of their π-electron bridge. The absorption spectra are presented. All compounds undergo five oxidations whereupon only the first two are reversible under semi-infinite cyclic voltammetry conditions. The spectra of the radical cations and dications of 1−5 were collected upon stepwise titration with SbCl5. All monoradical cations exhibit rather intense absorption bands in the NIR region that are assigned to optically induced charge transfer between the amine redox centers or between the amine redox center and aromatic bridge. It is suggested that with CH2Cl2 as solvent the charge in 1 + and 2 + is localized mainly at the peripheral amine redox centers whereas 3 + and 4 + are symmetrically delocalized systems with the highest charge density at the bridge. Upon increasing the solvent polarity, solvent induced symmetry breaking occurs as previously reported for the anthracene derivative 7 + . Less clear is the situation in 5 + . The nonalternant azulene derivative 4 behaves entirely different with respect to its optical and electrochemical properties if compared with the alternant naphthalene compound 6. The 1,3-azulene bridging unit turns out to mediate a strong electronic coupling combined with a low-oxidation potential.