Novel semisquaraine regioisomers: isolation, divergent chemical reactivity and photophysical properties

A zwitterionic semisquaraine 1,3-regioisomer which exhibits distinct photophysical properties and chemical reactivity was isolated. Uniquely, this isomer has been identified as the reactive intermediate in the squaraine dye formation reaction rather than the neutral 1,2-isomer and opens up new avenues for the synthesis of novel dyes for optoelectronic applications.