Photoelectrochemical and thermal characterization of aromatic hydrocarbons substituted with a dicyanovinyl unit

Abstract

Seven aromatic hydrocarbons bearing a dicyanovinyl unit were prepared to determine the relationship between both the number of aromatic rings and location of acceptor substituent on their thermal and optoelectronic properties. Additionally, the density functional theory calculations were performed. The obtained compounds showed temperatures of the beginning of thermal decomposition in the range of 137–289 °C, being above their respective melting points found between 88 and 248 °C. They were electrochemically active and showed quasi-reversible reduction process (except for 2-(phen-1-yl)methylene)malononitrile). Electrochemically estimated energy band gaps were below 3.0 eV, in the range of 2.10–2.50 eV. The absorption and emission spectra were recorded in CHCl3 and NMP and in solid state. All compounds strongly absorbed radiation with absorption maximum ranging from 307 to 454 nm ascribed to the intramolecular charge transfer between the donor and acceptor units. The aromatic hydrocarbons were luminescent in all investigated media and exhibited higher photoluminescence quantum yields in the solid state due to the aggregation induced emission phenomena. Electroluminescence ability of selected compounds was tested in a diode with guest-host configuration. Additionally, the selected compound together with a commercial N719 was applied in the dye-sensitized solar cell.