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- 1. Camille Biard ‘15 Southern Methodist University Chemistry/ Pre-Med
- 2. QuickSummaryofChemiluminescence What is it? It’s Importance Our Research Katie Krenek, Jian Cao of Dr. Lippert’s group
- 3. WhereDoesTheLightComeFrom? π (orbital) σ (orbital) Ground State π (orbital) σ (orbital) Excited State *The excited electron in the excited state then jumps back down into the sigma orbital and gives off the light. O-O bond is broken
- 4. Yue, Ling and Ya-Jun Liu. "Mechanism of AMPPD Chemiluminescence in a Different Voice." Journal of Chemical Theory and Computation (2013): 2300-2321.
- 5. Ouroptimizedm-Min structure Optimized Structure from Supporting Information of m-Min Comparison of S.I. vs OurWork
- 6. Frequency for SIT.S. m-MinO-O
- 10. IRCpathofT.S.m-MinO-O -4.16097, -998.903 0, -998.859 4.18633, -998.893
- 11. Conclusion &Acknowledgements - NewTransition state of m- MinO-O - More stable - Quicker product - Not a plausible reaction path
- 12. Acknowledgements -Dr.Tao andAshleigh Miller - Dr. Lippert and his research group - Southern Methodist University - All calculations were performed through SMU HPC, created by GaussView ‘09, and submitted to and calculated by Gaussian. - Undergraduate Research Association
- 13. -Yue, Ling, andYa-Jun Liu. "Mechanism of AMPPD Chemiluminescence in a DifferentVoice." Journal of ChemicalTheory and Computation 10 (2013): 2300-312. ACS Publications. Web. 21 Nov. 2013. <pubs.acs.org/JCTC>.
Editor's Notes
- Chemiluminescence is the emission of light by a substance that undergoes a chemical reaction without the increase of temperature. These reactions usually occur with highly oxidized molecules such as peroxide because the oxygen oxygen bond is relatively weak and when it breaks the atoms must reorganize themselves, which then give off the light. Chemiluminescent molecules are very important to us humans because of the light it emits and it has also been studied that these light emitting molecules can detect cancerous cell tissues; therefore, Chemiluminescent molecules are used to help detect the site of the tumor or cancerous cells by emitting light through those specific tissues of cancer patients. Our study revolves around computational chemical calculation studies of 1,2-dioxetanes, which are fairly well known light emitting molecules but are also unstable. We have been working with AMPPD which is fairly stable compared to other 1,2-dioxetanes and has been used in clinical diagnostics.
- This picture/ scheme is the proposed mechanism of AMPPD starting with the unstable intermediate AMPD. As described before, AMPPD is catalyzed by ALP. This then removes the phosphate group off the phenol. AMPPD becomes an unstable intermediate,m-AMPD, which then decays rapidly with the leaving group being the adamantone. m-MOB (anion) is formed, which is partially in the excited state and ground state. But, then relaxes completely into the ground state while releasing light. This is the proposed mechanism, but not the complete mechanism of the AMPPD decomposition. There is no actual known mechanism for this reaction.
- From our data and the supporting information data, both optimized forms through bond angles, dihedral angles, and bond lengths were the same. This shows that we have successfully reproduced the optimized structure of m-min… m-Min means the minimum or initial position before the structure m-AMPD begins to decay. Note, however, that m-Min is not m-AMPD because this optimized structure is lower energy and the oxygen oxygen bonds are broken.
- This is the normal mode of the Supportive information transition state m-MinO-O. Underneath, shows the imaginary frequency at this mode. Because of this imaginary frequency, we can determine that the transition stated found in Supportive information is an actual transition state of m-MinO-O. Also, please notice the oxygen oxygen movements and attraction towards each other.
- This looks similar to the normal mode we saw in the slide before; however, notice that the imaginary frequency is much lower and the oxygen oxygen do not attract towards each but rather the second oxygen (highlighted here) is more attracted to that carbon on the benzene ring. In fact, this imaginary frequency on the normal mode shows that we have discovered a new transition state.
- Here we’re looking at a perfect IRC path for the new found transition state of m-MinO-O. This IRC path defines the transition state by the gradient as well as which is the forward and backward steps.
- Here we’re looking at a perfect IRC path for the new found transition state of m-MinO-O. This IRC path defines the transition state by the gradient as well as which is the forward and backward steps.
- Because of this new found transition state, it has been concluded that through it’s imaginary frequency that it is more stable than the supporting information transition state; however, this new transition state is endothermic based off it’s IRC path and is not a plausible reaction path for m-AMPD. We will continue to study and understand this transition state, and also continue studying these’s highly unstable 1,2-dioextanes.