Synthesis and fluorescence properties of novel squarylium–boron complexes

Abstract

A novel boron complex based on a squarylium dye was synthesized by a simple two-step procedure starting from the pyrrole derivative. The absorption and fluorescence maxima of the squarylium–boron complex were slightly blue-shifted relative to those of the corresponding squarylium dye, and the fluorescence quantum yield of the former increased significantly. Deprotonation of the squarylium–boron complex led to the formation of the corresponding anion, with a further blue-shift of the absorption and fluorescence maxima.