Synthesis of a Near-Infrared Emitting Squaraine Dye in an Undergraduate Organic Laboratory
Date of Original Version
Squaraines are a class of organic fluorophores that possess unique photophysical properties, including strong near-infrared absorption and emission. The synthesis of many squaraines involves the condensation of an electron-rich aromatic ring with squaric acid. These reactions are generally refluxed overnight in a benzene–butanol solvent mixture. Reported herein are modifications to the synthesis of a squaraine dye that allowed the experiment to be performed in an undergraduate laboratory setting. The desired compound was formed after a 2-h reflux, using toluene as a co-solvent rather than the more toxic benzene. Moreover, the photophysical properties of the synthesized squaraine compound were analyzed in a separate laboratory period and led to important pedagogical opportunities about the absorption and fluorescence of organic compounds.
Marks, P.; Levine, M. “Synthesis of a Near-Infrared Emitting Squaraine Dye in an Undergraduate Organic Laboratory.” J. Chem. Educ. 2012, 89, 1186-1189. Available at: http://pubs.acs.org/doi/abs/10.1021/ed300187d