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Issue 23, 2011
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Reversible solid-state mechanochromic fluorescence from a boron lipid dye

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Difluoroboron β-diketone complexes are versatile light-emitting molecules that exhibit tunable emission in both solution and the solid state. Among this class of dyes, difluoroboron dibenzoylmethane-polylactide (BF2dbmPLA) polymers have been investigated for their molecular weight dependent fluorescence where the polymer chain plays an important role in BF2dbm solid-state emission. Here the substituent effects were further examined with a lipid chain replacing polylactide. Surprising process dependent and reversible mechanochromic fluorescence was discovered for the boron dodecane complex (BF2dbmOC12H25). A thermally annealed spin-cast film of the lipid dye on glass exhibited blue fluorescence under UV light but after shearing or scratching, the mechanically perturbed region turned yellow-green. The blue coloration could be rapidly recovered by thermal treatment of the film. The phenomena were investigated by steady-state fluorescence spectroscopy at room, low, and high temperatures, in situfluorescence microscopy, fluorescence lifetime measurements, and X-ray diffraction. Consistent with previous findings, the ordered-to-amorphous structural change that occurs upon mechanical perturbation may increase molecular rotational freedom, allowing for more efficient excimer emission, which typically occurs at longer wavelengths.

Graphical abstract: Reversible solid-state mechanochromic fluorescence from a boron lipid dye

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Publication details

The article was received on 10 Nov 2010, accepted on 24 Jan 2011 and first published on 23 Feb 2011

Article type: Paper
DOI: 10.1039/C0JM03871G
J. Mater. Chem., 2011,21, 8295-8299

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    Reversible solid-state mechanochromic fluorescence from a boron lipid dye

    G. Zhang, J. P. Singer, S. E. Kooi, R. E. Evans, E. L. Thomas and C. L. Fraser, J. Mater. Chem., 2011, 21, 8295
    DOI: 10.1039/C0JM03871G

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