Solvent-Sensitive Emitting Urea-Bridged bis-BODIPYs:Ready Access by aOne-Pot Tandem Staudinger/Aza-Wittig Ureation

Abstract

Herein we describe the synthesis and computationally aided photophysical characterization of a new set of urea-bridged bis-BODIPY derivatives. These new dyads are efficiently obtained by a one-pot tandem Staudinger/aza-Wittig ureation protocol, from easily accessible meso-phenyl ortho-azidomethyl BODIPYs. These symmetric bis-BODIPYs outstand by a high absorption probability and excellent fluorescence and laser emission in less polar media. Nevertheless, this emission ability decreases in more polar media, which is ascribed to a light-induced charge-transfer from the urea spacer to the dipyrrin core, a process that can be modulated by appropriate changes in the substitution pattern of the BODIPY core. Furthermore, this ureation protocol can also be employed for the direct conjugation of our BODIPY-azides to amine-containing compounds, thus providing access to fluorescent non-symmetric ureas.

Herein we describe the synthesis and computationally aided photophysical characterization of a new set of urea-bridged bis-BODIPY derivatives. These new dyads are efficiently obtained by a one-pot tandem Staudinger/aza-Wittig ureation protocol, from easily accessible meso-phenyl ortho-azidomethyl BODIPYs. These symmetric bis-BODIPYs stand out for their high absorption probability and excellent fluorescence and laser emission in less polar media. However, their emission efficiency decreases in more polar environments due to a light-induced charge-transfer process from the urea spacer to the dipyrrin core, which can be modulated through structural modifications of the BODIPY units. Additionally, the described ureation strategy enables the direct conjugation of BODIPY azides with amine-containing compounds, providing a versatile route to non-symmetric fluorescent ureas with potential applications in photonics and sensing.