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Eric Sundberg and Lijuan Li California State University, Long Beach

Structural Characterization and Electronic Properties of a Cyclic Non-heme-iron-dinitrosyl Complex: [Fe(NO) 2 Imidazole] 4. Eric Sundberg and Lijuan Li California State University, Long Beach. Nitric Oxide Chemistry. 30 Years ago: A major contributor to smog

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Eric Sundberg and Lijuan Li California State University, Long Beach

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  1. Structural Characterization and Electronic Properties of a Cyclic Non-heme-iron-dinitrosyl Complex: [Fe(NO)2Imidazole]4 Eric Sundberg and Lijuan Li California State University, Long Beach

  2. Nitric Oxide Chemistry • 30 Years ago: • A major contributor to smog • An ingredient in cigarette smoke and automobile exhaust • A suspected carcinogen • An ozone depleting agent • Toxic, noxious chemical Koshland, D. E., Jr. Science 1992, 258, 1861-1902

  3. Nitric Oxide Chemistry • In 1992, it was named the “Molecule of the Year” by the journal Science in an article titled, “NO News is Good News” • In 1998 three gentlemen were awarded the nobel prize in medicine and physiology for their work involving the biological aspects of nitric oxide

  4. Nitric Oxide Chemistry Furchgott Ignarro Murad Discovered that nitric oxide works as a signaling molecule in the cardiovascular system http://www.nobel.se/medicine/laureates/1998/index.html

  5. Maintains blood pressure by dilating blood vessels Kills foreign invaders Involved in neurotransmission Involved in learning and memory processes Controls platelet aggregation Stimulates penile erections Nitric Oxide Chemistry Numerous Physiological Functions Feldman, P. L.; Griffith, O. W.; Stuehr, D. J. Chem Eng. News 1993, 71 (Dec), 26-38

  6. Nitrosyl (NO) on a hemoglobin molecule Nitrosyl attached to a non-heme molecule Heme Versus Non-heme + NO Muller, B.; kleschyov, A. L.; Stoclet, J. C. Br. J. Pharm. 1996, 119, 1281-1285

  7. Outline Non-heme iron Dinitroyls Synthesis Classification Characterization EPR and NMR Stability UV-vis Electrochemistry FT-IR X-ray Crystallography Density Functional Theory

  8. Synthesis Fe(CO)2(NO)2 + C3H4N2 Starting Material: Dicarbonyldinitrosyliron(0) Ligand: Imidazole

  9. After 2 Hours: After 24 Hours: Synthesis

  10. Characterization

  11. X-ray Crystallography shows a cyclic compound with an acetone molecule trapped inside Characterization

  12. Materials and Methods • Recrystallized [Fe(NO)2Im]4 • Nuclear Magnetic Resonance • Dissolved 50mg of sample into 2 mls of deuterated THF and transferred to a NMR tube • AC200 Spectrometer • Electron Paramagnetic Resonance • Dissolved 2 mg of sample into degassed 1 ml of THF and transferred to EPR tube • Brooker EMX Model EPR Spectrometer

  13. Materials and Methods • Electrochemistry • 3 electrode system with a gold working electrode • THF was used as the solvent • Scan Rate of 100 mV sec-1 • 10mM [Fe(NO)2(Imidazole)]4 solutionand a 0.1M electrolyte solution, (tetrabutylammonium perchlorate) • Computer Controlled Electrochemical Analyzer Autolab Electrochemical Insturments http://www.ecochemie.nl/

  14. Materials and Methods • UV-vis Spectroscopy • Varian 300 Bio UV-vis spectrophotometer • Dilution Series in THF: 0.1-0.8 mM Cary Uv-vis Spectrometer www.varianinc.com

  15. Materials and Methods • Stability • FT-IR spectroscopy (Nicholet 380 Spectrometer) • 0.2mM in THF at 15 and 30 minutes • Spin Density Functional Theory • Performed using X-ray crystallographic coordinates • Dr. Fu-Ming Tao at Cal. State Univ. Fullerton

  16. Nuclear Magnetic Resonance H1 1H NMR (H2&H3) (H1) H2&H3 9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1.0 0

  17. Nuclear Magnetic Resonance 13C NMR C1 C2&C3 C2&C3 C1 240 210 180 150 120 90 60 30 ppm

  18. Electron Paramagnetic Resonance g=2.03 20G Hyperfine Structure

  19. Electrochemistry

  20. UV-vis Spectroscopy MLCT d-d transitions

  21. Stability under Oxygen

  22. Spin Density Functional Calculations • Will provide wavefunction analysis of the molecule •  = a + b + c… • A diagram of the electron density on the molecule

  23. Spin Density Functional Calculations

  24. Spin Density Functional Calculations Single- Substituted Product Cyclic Product

  25. Conclusion • [Fe(NO)2Im]4 has been characterized by • X-ray Crystallography and FT-IR Spectroscopy • NMR and EPR techniques • Electrochemistry showed 2 chemically reversible reductions • UV-vis spectroscopy showed MLCT and d-d orbital transitions

  26. Conclusion • Low stability of compound in solution when exposed to oxygen • Spin Density Functional Theory showed excess electronic density on the imidazole • Potential Medicinal Applications

  27. Future Studies • Mass spectrometry • Elemental analysis • NMR studies of decomposed sample • Laser flash photolysis

  28. Acknowledgements • Dr. Lijuan Li • Dr. Ximeng Wang • The Beckman Scholars Foundation • Howard Huges Medical Institute

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