o-Hydroxydibenzoylmethanate of boron difluoride: A complex with multi-stimuli-responsive emission effects

Aromatic Difluoroboron β-Ketoiminate Complexes: Effect of Substituents on Mechanofluorochromism and Polymorphic Behavior

Aromatic difluoroboron β-ketoiminate complexes (ketimBF2) are structural nitrogen-containing analogues of aromatic difluoroboron β-diketonates (diketBF2). Aggregation-induced emission (AIE) and polymorphic behavior allow ketimBF2 to exhibit mechanofluorochromic (MFC) properties. A detailed comparative study of the luminescence of a wide range of ketimBF2 with H- and CH3-substituents of nitrogen atom and diketBF2 with various substituents of the chelate ring (methyl, phenyl, toluoyl, anisoyl, biphenyl, naphthyl, anthracyl) in the solid state was carried out. As a result, regularities of the influence of substituents on the luminescent and MFC properties for 21 dyes have been established. Replacing one oxygen atom in diketBF2 with nitrogen atom in the chelate ring (H-substituted ketimBF2) changes the nature of the molecular stacking in crystals, which is manifested in different MFC properties. The introduction of a methyl group into the chelate ring (CH3-substituted ketimBF2) induces steric hindrance, which prevents the efficient formation of supramolecular structures and, consequently, leads to the shortest-wavelength monomeric emission in the solid state in comparison with oxygen and H-substituted nitrogen analogues. Methoxy derivative of H-substituted ketimBF2 exhibits non-reversible fluorochromic switching after annealing and can be used as temperature indicator to control unauthorized heating of temperature-sensitive substances during transportation and storage.

Polymer films doped with boron difluoride ortho-hydroxydibenzoylmethanates: Solvatochromism and solvent-induced exciplex formation

The spectral properties and solvatochromic behavior of boron difluoride ortho-hydroxydibenzoylmethanates in polymer matrices with different polarity (polystyrene, polyvinyl chloride, polycarbonate, poly(methyl methacrylate)) were investigated. The specific interaction of polystyrene, polycarbonate and poly(methyl methacrylate) with the investigated fluorophores was revealed. It was shown that the dyes are capable to form exciplexes with phenyl rings of polystyrene. The spectral properties of polystyrene films doped with boron difluoride ortho-hydroxydibenzoylmethanates, which were obtained by the pouring method, significantly depend on the solvent from which they were formed. This makes it possible to control the luminescence color of the films at the manufacturing stage.

Synthesis, photophysical and electrochemical properties of novel and highly fluorescent difluoroboron flavanone β-diketonate complexes

A convenient method for the synthesis of flavanone difluoroboron complexes with strong absorption and fluorescence properties is described.