Modulation of Difluoroboron Beta-Diketonate Solid-State Luminescence

Liu, Tiandong, Department of Chemistry, University of Virginia
Fraser, Cassandra, Department of Chemistry, University of Virginia

The study of difluoroboron [3 - diketonates(BFzbdks) achieved significant success in the past decade. Room temperature phosphorescence in poly(lactic acid) and mechanochromic luminescence (ML) were discovered and lead to potential applications in tumor hypoxia imaging and as mechanical force sensors. However, there are still important goals to expand their practical utilization. We systematically investigated BFzbdks luminescence in the solid state to gain greater insight into factors influencing the luminescence mechanism. Bromide, a known heavy atom, was introduced into difluoroboron benzoylnaphthoylmethane dyes to perturb their intramolecular charge transfer (ICT) emission. The heavy atom effect is more pronounced when the bromide is placed on the naphthyl ring than when it was on the phenyl group, which supports the hypothesis that the major arene donor is dominant in the ICT and emission process. The results demonstrate a new method to modulate BFzbdk emission, both singlet and triplet properties, and can help researchers to design fluorophores with desired photophysical properties. The mechanochromic luminescence of BFzbdks is related to intermolecular interactions and molecular stacking in the solid state. Diketonate aryl substituents were expected to influence ir1 dye packing and to alter 11-1: interactions. Thus, the arene effect in BFzbdk mechanochromic luminescence was examined. In brief, the ML behavior varies with arer1e substituent, though wavelength shifts upon smearing are less pronounced for these unsubstituted dyes compared to previously reported systems with electron donating alkoxyl substituents.

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MA (Master of Arts)
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