Crystal Structure and Triboluminescence 2. 9-Anthracenecarboxylic Acid and Its Esters

Abstract

Triboluminescence activity is usually assumed to be a consequence of crystal dissymmetry; however, the multitude of reports of centrosymmetric triboluminescent materials cast doubt on that assumption. We examine here the connection between triboluminescence and crystal symmetry without prejudice, by synthesizing 12 esters of 9-anthracenecarboxylic acid and correlating their triboluminescence activity and that of the acid with crystal structure, purity, and photoluminescence. In this series, a noncentrosymmetric crystal structure is necessary but not sufficient for triboluminescence in relatively pure materials; impurities are necessary for triboluminescence activity in all centrosymmetric and one noncentrosymmetric materials. Crystallization motif and other structure factors were only weakly correlated with triboluminescence. The results provide evidence in support of a charge separation and recombination mechanism for the excitation of the triboluminescence.Supporting Information Available: For 3-4 and 6-12, complete lists of atomic coordinates, bond lengths, bond angles, and anisotropic displacement coefficients (52 pages); for 2-4 and 6-12, correlation of crystal cell parameters with stacking motif (1 page); and observed and calculated structure factors (46 pages). Ordering information is given on the current masthead page. CM960438R

Elastico-mechanoluminescence and crystal-structure relationships in persistent luminescent materials and II–VI semiconductor phosphors

“…The EML of persistent luminescent materials where the dopant is rare earth ions such as Eu 2 þ can be understood with respect to the following steps [56]: Many centric crystals such as saccharin [69] (space group P2 1 /a), triphenylphosphine [70] (space groups P2 1 /c and P1 ) , triphenylphosphine oxide [70] (space groups P2 1 /c and Pbca), 1-ethyl-2-methylpropyl 9-anthracenecarboxylate [71] (space group P2 1 /c), isopropyl 9-anthracenecarboxylate [71] (space group Pbca), 9-anthracenecarboxylate [71] (space group Pbca), and 1-methylpropyl 9-anthracenecarboxylate [71] (space group P1) grown from impure materials exhibit fracto ML, but such centric crystals grown from purified materials do not show fracto ML. These results indicate that the crystal-structures near the impurities may be in the non-centrosymmetric structures.…”

FLASHFOAM : a triboluminescent polymer foam for mechanical sensing.

“…The nominal density of all specimens was 0.08 g/cm 3 . Specimens were tested in a Dynatup 8250 Drop Tower impact tester (Instron Corp., Canton, MA).…”

“…At low magnifications, Figure 3a, the cell structure is indistinguishable to conventional unloaded structural polyurethane foams. 7,8 The foam is comprised of equi-axed cells and at the density of interest, ≈ 0.08 g/cm 3 , the cells are typically 300 µm to 500 µm in diameter. None of the powder additive was observed within the interior of the cells.…”

“…2 However, it is clear from other publications that the phenomena of triboluminescence cannot be comprehensively understood from the simple explanation invoked for sugar, as impurities can drive the emission in centrosymmetric structures. 3 Further, emission from non-crystalline sources is common as well. 4 With regard to the application of TL materials to damage sensing, work has been reported where TL particulates have been incorporated into fully dense polymer resins.…”

Crystal Structure and Triboluminescence Spectrum of A μ2-(ONC5H5) Bridging Dinuclear Europium(III) Complex

“…Several theories are raised to explain why the crystal having a centrosymmetric space group still exhibits triboluminescent activity. The importance of trace dopants in determining triboluminescent activity was proven for saccharin [7] and anthracene derivatives [8]. Random impurities may create local dissymmetry.…”