Photophysical properties of isoelectronic oligomers with vinylene, imine, azine and ethynylene spacers bearing triphenylamine and carbazole end-groups

Ten symmetrical oligomers containing either triphenylamine or carbazole substituents as end-groups and 1,4-phenylenevinylene, 1,4-phenylene imine, azine and 1,4-phenylene ethynylene as π-spacers, have been synthesized by polycondensation reactions between aromatic aldehydes (4-formyltriphenylamine and 3-formyl N-hexylcarbazole) or iodides (4-iodotriphenylamine and 3-iodo N-hexylcarbazole) with bisphosphonate derivative, 1,4-diaminobenzene, hydrazine or 1,4-diethynylbenzene, respectively. These oligomers are models for the corresponding conducting polymers, have a well-defined molecular structure, can be highly purified using common methods and processed as thin films by vacuum evaporation, dip or spin coating. The oligomers preserve all of the properties and potential applications of the corresponding polymers. The structural characterization of these oligomers was performed using usual spectroscopic methods (1H-RMN, FT-IR and DSC) and their photophysical properties were analyzed by UV–Vis and fluorescence spectroscopy. Their redox properties were studied by cyclic voltammetry.

Graphical abstractA series of symmetrical arylamine oligomers containing triphenylamine and 3-carbazolyl N-hexyl groups as ends were prepared. An investigation of their optical and redox properties has evidenced a dependence on the nature of π-spacer and arylamine group.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► A series of symmetrical oligomers having two donors (triphenylamine or carbazole groups) have been synthesized and characterized. ► The donor end-groups are separated by various π-spacers. ► The position of λmax in the absorption and emission spectra is related to the donor and spacer nature. ► For donor groups the bathocromic shift of λmax is in the order carbazole < triphenylamine. ► For π-spacer the bathocromic shift of λmax is in the order phenylene–ethynylene < phenyleneimine < azine < phenylenevinylene.