The Spectroscopic-Assisted Studies on Photophysics and Mechanochemistry of Anthracene-Based Materials
A series of 2,6-dialkoxyanthracenes are synthesized and their photophysical properties in liquid solution and solid state are studied. Both spectral lineshapes and luminescence decay kinetics of these molecules in dilute solution or in a polymer matrix are identical. We identify a conformational change in solution that leads to two emissive states that can interconvert. In the solid state, the crystal structures of 2,6-dialkoxyanthracenes change significantly with lengthening alkoxy chains from methoxy to hexyloxy, evolving from herringbone structures to face-to-face two-dimensional sheets. The results from temperature-dependent experiments on single crystals indicate the intermolecular couplings between molecules with longer alkoxy chains are quite different from the J-type aggregates seen in crystalline anthracene. By tuning the side chain length and modifying the crystal structures of 2,6-dialkoxyanthracenes, we can change the luminescence properties of the Frenkel excitons that exist in the crystals.
The 9-tert-butylanthracene (TBA) can undergo a reversible photoisomerization to the Dewar isomer. The dependence of both the formation and reversion of the Dewar isomer on pressure was investigated using absorption and fluorescence spectroscopy with TBA doped polystyrene as a model system. It is demonstrated that both the photoisomerization and its reverse reaction rates are decreased with higher pressure.