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JCE Featured Molecules
William F. Coleman
Molecular Models of Compounds in Lightsticks January 2009 Featured Molecules The article “Glowmatography”, by Thomas S. Kuntzleman, Anna E. Comfort, and Bruce W. Baldwin, is the source of this month’s Featured Molecules (1). Three molecules from the paper have been added to the collection and several rhodamine derivatives were featured in the November 2007 column (2). The energy transfer agent in the lightsticks is 1,2-dioxetanedione, a cyclic peroxide and high energy dimer of carbon dioxide. Students at all levels would be interested to learn that the chemistry of a toy can be used in a wide variety of applications. For example, 1,2-dioxetanedione embedded in nanoparticles has recently been used to image hydrogen peroxide in cells (3).
1,2-Dioxetanedione, the energy transfer agent in lightsticks, is a cyclic peroxide and high energy dimer of carbon dioxide.
Wellesley College Wellesley, MA 02481
A number of polyaromatic compounds are included in Table 1 of the source paper (1). Rubrene, 5,6,11,12-tetraphenylnaphthacene, when optimized at the PM3 level, shows an interesting chiral twist to the napthacene backbone of about 37°. We find that twist to be present, but reduced to about 10° at the HF/6-31G(d) level, and a similar magnitude at the B3LYP/631G(d) level. A more complete DFT study is underway as our results do not agree with those of Käfer and Witte who find a somewhat larger twist angle (4). Those authors point out that the crystal structure of rubrene shows no twist. Rubrene also has many uses other than entertainment. It is an organic semiconductor used in LEDs, solar cells, and transistors, and has recently been shown to produce interesting self-assemblies on metal surfaces (5). Another polyaromatic compound, 5,12-bis(phenylethynyl) naphthacene, shows the expected planar structure and the molecular orbitals are consistent with a high degree of delocalization. This compound has been used to activate the bleaches in commercial teeth-whitening products (6). Other molecules from Table 1 (1) would provide students the qualitative experience of leaning about applications beyond the lightstick and the quantitative experience of optimizing structures to explore the ways in which the various substituents pack around the polycene backbone. Literature Cited
Rubrene, 5,6,11,12-tetraphenylnaphthacene, is a fluorescent dye contained in commercial lightsticks.
1. Kuntzleman, Thomas S.; Comfort, Anna E.; Baldwin, Bruce W. J. Chem. Educ. 2009, 86, 64. 2. Coleman, William F. Molecular Models of Dyes. J. Chem. Educ. 2007, 84, 1798; http://www.jce.divched.org/JCEWWW/Features/ MonthlyMolecules/2007/Nov/ (accessed Nov 2008). 3. Lee, D; Khaja, S; Velasquez, C. J.; Dasari, M.; Sun, C.; Petros, J.; Taylor, W.; Murthy, N. Nat. Mater. 2007, 6, 765. 4. Käfer, D; Witte, G. Phys. Chem. Chem. Phys. 2005, 7, 2850– 2853. 5. The Changing Face of Rubrene—nanotechweb.org; http://nanotechweb.org/cws/article/lab/35981 (accessed Nov 2008). 6. Teeth Whitening Agents Invention—FreshPatents.com; http:// www.freshpatents.com/Teeth-whitening-agents-dt20081023ptan20080260660.php (accessed Nov 2008).
Supporting JCE Online Material
http://www.jce.divched.org/Journal/Issues/2009/Jan/abs128.html Full text (HTML and PDF) with images in color Links to cited URLs and JCE articles Supplement Find “Molecular Models of Compounds in Lightsticks” in the JCE Digital Library at http://www.JCE.DivCHED.org/JCEWWW/ Features/MonthlyMolecules/2009/Jan/ 5,12-Bis(phenylethynyl)naphthacene is another fluorescent dye used in lightsticks.
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The molecules added to the collection this month are 1,2-dioxetanedione; 5,12-bis(phenylethynyl)naphthacene; rubrene (5,6,11,12-tetraphenylnaphthacene)
Journal of Chemical Education • Vol. 86 No. 1 January 2009 • www.JCE.DivCHED.org • © Division of Chemical Education
