Make the ylides shine: synthesis and structure–property relationships of phospha-squaraines

Abstract

We report the synthesis and full characterization of a family of four phospha-squaraine dyes, obtained in a single step from squaric acid derivatives. Their structure–property relationships are investigated through a joint experimental/theoretical approach. All of these exotic ylides display strong absorbtion and emission in the red region of the spectrum, a rare feature for phosphorus ylides. Furthermore, they exhibit enhanced photostability compared to a standard squaraine reference.