Thiazole Boron Difluoride Dyes with Large Stokes Shift, Solid State Emission and Room‐Temperature Phosphorescence

The small Stokes shift and weak emission in the solid state are two main shortcomings associated with the boron‐dipyrromethene (BODIPY) family of dyes. This study presents the design, synthesis and luminescent properties of boron difluoro complexes of 2‐aryl‐5‐alkylamino‐4‐alkylaminocarbonylthiazoles. These dyes display Stokes shifts (Δλ, 77–101 nm) with quantum yields (ϕ (FL)) up to 64.9 and 34.7 % in toluene solution and in solid state, respectively. Some of these compounds exhibit dual fluorescence and room‐temperature phosphorescence (RTP) emission properties with modulable phosphorescence quantum yields (ϕ (PL)) and lifetime (τ(p) up to 251 μs). The presence of intramolecular H‐bonds and negligible π‐π stacking revealed by X‐ray crystal structure might account for the observed large Stokes shift and significant solid‐state emission of these fluorophores, while the enhanced spin‐orbit coupling (SOC) of iodine and the self‐assembly driven by halogen bonding, π‐π and C−H(…)π interactions could be responsible for the observed RTP of iodine containing phosphors.