清洁能源化学与材料实验室知识库

Obtaining π-conjugated room temperature ionic liquids (RTILs) is difficult because of the relatively strong π–π interaction among the π-moieties. Existing strategies by using bulky counterions greatly hindered further property optimization and potential applications of these intriguing functional fluids through simple ion exchange. Herein, four naphthalene-functionalized, π-conjugated RTILs with small counterions (Br⁻) have been facilely synthesized with high yields. Our strategy is to attach branched alkyl chains to the cationic backbone of the target compounds (2 a–d), which effectively tune inter- and intramolecular interactions. Compounds 2 a–d have satisfactory thermal stability (up to 300 °C) and low melting points (<−19 °C). Rheological measurements revealed the fluid character of 2 a–d, whose viscosity decrease with the increase of the alkyl chain length and temperature. The presence of the π-conjugated naphthalene moiety imparts 2 a–d photoluminescent properties in bulk solutions. Moreover, the absence of strong π–π stacking among the naphthalene units in solvent-free states enables them to be used as a new generation of photoluminescent inks.