Azoimidazolium Salts as a Platform for Persistent Neutral Aminyl Radicals and Mesoionic Carbene Au(I) Complexes as Cell-Permeable Fluorophores.

Abstract

Strategic electronic matching between imidazolium precursors and aryldiazonium salts enables the synthesis of azoimidazolium derivatives via an operationally simple, base-promoted protocol that circumvents the need for column chromatography. The resulting azoimidazolium scaffolds serve as precursors of highly persistent neutral aminyl radicals, which exhibit remarkable stability with negligible decay after 3 weeks in the solid state. Furthermore, these salts were successfully employed as a versatile platform to access novel Au(I)-mesoionic carbene (MIC) complexes. When evaluated in living human glioblastoma A172 cells, these Au(I)-MIC acted as efficient, cell-permeable fluorophores with an unprecedented substituent-governed, dual-channel readout spanning from the green to the red region, governed by donor strength of the peripheral substituents.