Asymmetric Squaraine Dyes: Spectroscopic and Theoretical Investigation

A joint experimental and theoretical study is presented of two asymmetric squaraine dyes and their parent symmetric dyes. The definition of reliable essential-state models for asymmetric squaraines sheds light on the intriguing spectroscopic behavior of this class of molecules, showing inverted and normal solvatochromism in absorption and emission, respectively. This behavior is related to charge redistribution in the excited state, with important implications for optimal design of asymmetric dyes for solar cell applications.