Thienyl Difluoroboron β-Diketonates in Solution and Polylactide Media

Difluoroboron β-diketonates (BF₂bdks) have impressive optical properties in both solution and the solid state. In particular, both fluorescence and roomerature phosphorescence are present when the dyes are confined to a rigid matrix, such as poly(lactic acid) (PLA). To expand the current knowledge and colour range capabilities of this unique type of multi-emitting chromophore, a series of thienyl-substituted BF₂bdk complexes have been synthesized. The photophysical properties were investigated in dichloromethane solution and in the solid state as dye/PLA blends. By varying donor ability, i.e. methyl, phenyl, methoxy, and thienyl substituents, and by changing the dye loading in the PLA media (0.1-10% dye loading) red-shifted emission was achieved, which is important for biological imaging applications. In dilute CH₂Cl₂ solution, complexes exhibited absorptions ranging from 350 to 420nm, solid-state fluorescence in PLA ranging from 390 to 500nm, and oxygen sensitive phosphorescence ranging from 540 to 585nm in PLA blends. Promising candidates as dye/PLA blends serve as models for dye-polymer conjugates for application as biological oxygen nanoprobes.