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Synthesis and Characterization of Metallo-tetraarylazadipyrromethene Complexes

Synthesis and Characterization of Metallo-tetraarylazadipyrromethene Complexes. Anne Lam Damali Greenaway Mentors: Dr. Chris Hansen and Dr. Jianguo Shao. July 05, 2013. Objectives. To synthesize a ligand and metal complexes

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Synthesis and Characterization of Metallo-tetraarylazadipyrromethene Complexes

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  1. Synthesis and Characterization of Metallo-tetraarylazadipyrromethene Complexes Anne Lam Damali Greenaway Mentors: Dr. Chris Hansen and Dr. Jianguo Shao July 05, 2013

  2. Objectives • To synthesize a ligand and metal complexes • To characterize complexes using Electro-chemistry, IR, and UV-visible Spectroscopy

  3. Causes for Study • Metallo-tetraarylazadipyrromethene complexes exhibit potential application as • fluorescent chemosensors-molecules that change their fluorescence in response to substrate binding • in vitro fluorophores– molecules employed in  biochemistry, protein studies, and cell analysis • photosensitive drugs in Photodynamic Therapy

  4. Jablonski Diagram for the PDTprocess Our compounds exhibit strong absorption in the visible range (400 – 780 nm).

  5. Synthesis of Free-base Ligand 1,4 Michael Addition Reflux with CH3CO2NH4 Products confirmed by H-NMR

  6. Synthesis of Metallo-complexes Reflux with CH3CO2NH4 and CoCl2 · 6H2O 22 h Reflux with Ni(CH3CO2)2 · 4H2O 22 h Product purities tested with TLC Reflux with Cu(CH3CO2)2 1 h (free-base ligand) Ni Co Cu (pure)

  7. IR Spectra Ni complex 1Free Base (tetraarylazadipyrromethene)

  8. UV-Visible Spectra in CH2Cl2 Cu FB Co Ni 300 400 500 600 700 800 1Free Base (tetraarylazadipyrromethene) Wavelength (nm)

  9. UV-Visible Spectra in DMF Cu FB Co Ni 300 400 500 600 700 800 1Free Base (tetraarylazadipyrromethene) Wavelength (nm)

  10. Electrochemical Introduction • A potential is applied to an electrode immersed in a solution, forcing the oxidation/reduction of the analyte. • The concentration ratio of the Oxidized and Reduced species (near the electrode) adopts a value consistent with the Nernst Equation. • The magnitude of the current is then determined by • Electron-Transfer – the oxidation or reduction of analyte • Mass- Transfer- the transport (diffusion) of analyte to or from the electrode surface in an attempt to equalize the concentrations

  11. Cyclic Voltammetry (Theory) E1/2 E1/2 (-) (+) Reduction Oxidation (Electron Addition) (Electron Withdrawal) - e- A- A A A+ + e-

  12. Cyclic Voltammetry CH2Cl2,0.1M TBAP Oxidation Reduction * * -2.00 -1.50 -1.00 -0.50 0.00 0.50 0.75 1.00 1.25 1.50 Potential (V vs SCE) Potential (V vs SCE)

  13. Oxidations in CH2Cl2, 0.1M TBAP 0.50 0.75 1.00 1.25 1.50 Potential (V vs SCE)

  14. Reductions in CH2Cl2, 0.1M TBAP * * -2.00 -1.50 -1.00 -0.50 0.00 Potential (V vs SCE)

  15. Reductions in Pyridine, 0.1M TBAP * * -2.00 -1.50 -1.00 -0.50 0.00 Potential (V vs SCE)

  16. Copper Reductions DPV a) In Pyridine CV DPV b) In CH2Cl2 CV -1.50 -1.00 -0.50 0.00 Potential (V vs SCE)

  17. Different Scan Rates, CH2Cl2, 0.1 M TBAP Diffusion-Controlled mV/s 300 250 200 150 100 50 A B E C D -1.6 -1.2 -0.8 -0.4 0.0 0.0 0.4 0.8 1.2 Potential (V vs SCE) Potential (V vs SCE)

  18. Different Scan Rates, CH2Cl2, 0.1 M TBAP Diffusion-Controlled mV/s 300 250 200 150 100 50 A B E C D -1.6 -1.2 -0.8 -0.4 0.0 0.0 0.4 0.8 1.2 Potential (V vs SCE) Potential (V vs SCE)

  19. Conclusion • All three metallo-complexes exhibit two common reversible oxidations with greater relative ease as compared to the free base ligand. • Ni and Co complexes share reductive properties from 1st and 2ndpyrrole electron additions and 3rd (and likely 4th) phenyl electron additions. • Cu complex displays unique electro-reduction properties and the first reduction takes place on the Cu(II) center. • All redox processes are diffusion-controlled.

  20. Future Work • Purification is needed for Co and Ni complexes. • Fluorescence spectra will be examined. • Are Co, Ni and Cu complexes active catalysts for the DDT reductive dechlorination? • To find the solution why Cu complex has a special electro-reduction behavior as respect to Ni and Co complexes. • Different substituted groups can be introduced into phenyl rings to fine-tune the properties.

  21. Acknowledgments • This research was supported by Midwestern State University’s UGROW program and funded by the Welch Foundation. • Thanks to MSU chemistry department, Dr. Rincon, program director, and Drs. Hansen and Shao for advice and mentorship.

  22. References • Besette, A.; Ferreira, J. G.; Giguere, M.; Belanger, F., Desilets, D.; Hanan, G. S. Inorg. Chem. 2012, 51, 12132-12141. • O’Connor, A.; Mc Gee, M.; Likar, Y.; ponomarev, V.; Callanan, J. J.; O’shea, D. F.; Byrne, A.; Gallagher, W. Int. J. Canc. 2011, 130, 705-715. • Aniello, P.; Gallagher, J.F.; Muller-Bunz, H.; Wolowska, J.; McInnes, E. J.L.; O’Shea, D. F. Dalton Trans. 2009, 273-273. • Teets, T.; Partyka, J.; Updegraff III, J. J.; Gray, T. Inorg. Chem. 2008, 47, 2338-2346. • Gorman, A.; Killoran, J.; O’Shea, C.; Kenna, T.; Gallagher,W.M.; O’Shea, D. F. J. Am. Chem. Soc. 2004, 126, 10619-10631. • Kissinger, P. T.; Heineman, W. R.; J. Chem. Educ.1983, 60, 702-706.

  23. Questions?

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