Benzothiazole-substituted boron difluoride formazanate dyes

Abstract

The incorporation of benzothiazole heterocycles into existing molecular frameworks has resulted in the production of a wide range of multifunctional molecular materials. However, this strategy has not yet been explored for an emerging class of boron difluoride dyes, derived from formazanate ligands, which often exhibit tuneable redox and optical properties. Here, we address this gap in the literature and describe the synthesis and characterization of a series of benzothiazole-substituted BF2 formazanates. The incorporation of benzothiazole resulted in absorption profiles that were shifted to lower energies and reduction events that were shifted to more positive potentials when compared to those of the triphenyl-substituted analogue. These results were corroborated by DFT and TD-DFT calculations that suggest that the incorporation of benzothiazole units results in stabilization of the LUMO level thereby narrowing the HOMO-LUMO gaps of this new family of readily accessible dyes. Fine-tuning of these parameters was demonstrated through variation of the supporting N-aryl substituents appended to the formazanate ligand backbone.