Wright State University CORE Scholar Browse all Theses and Dissertations Theses and Dissertations 2012 Synthesis of Mixed Metal Trinuclear Cluster of Molybdenum and Tungsten and Their Electrochemistry in Ionic Liquids Jessica Ann Davis Wright State University Follow this and additional works at: https://corescholar.libraries.wright.edu/etd_all Part of the Chemistry Commons Repository Citation Davis, Jessica Ann, "Synthesis of Mixed Metal Trinuclear Cluster of Molybdenum and Tungsten and Their Electrochemistry in Ionic Liquids" (2012). Browse all Theses and Dissertations. 637. https://corescholar.libraries.wright.edu/etd_all/637 This Thesis is brought to you for free and open access by the Theses and Dissertations at CORE Scholar. It has been accepted for inclusion in Browse all Theses and Dissertations by an authorized administrator of CORE Scholar. For more information, please contact [email protected]. SYNTHESIS OF MIXED METAL TRINUCLEAR CLUSTER OF MOLYBDENUM AND TUNGSTEN AND THEIR ELECTROCHEMISTRY IN IONIC LIQUIDS. A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science By JESSICA ANN DAVIS B.A., Chemistry, East Carolina University, 2009 2012 Wright State University WRIGHT STATE UNIVERSITY GRADUATE SCHOOL August 18, 2012 I HEREBY RECOMMEND THAT THE THESIS PREPARED UNDER MY SUPERVISION BY Jessica Ann Davis ENTITLED Synthesis of Mixed Metal Trinuclear Cluster of Molybdenum and Tungsten and Their Electrochemistry in Ionic Liquids BE ACCEPTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF Master of Science. ____________________________ Vladimir Katovic, Ph.D. Thesis Director ___________________________ David Grossie, Ph.D., Chair Department of Chemistry Committee on Final Examination ____________________________ Vladimir Katovic, Ph.D. ____________________________ David Grossie, Ph.D. ____________________________ David Dolson, Ph.D. ____________________________ Andrew Hsu, Ph.D. Dean, School of Graduate Studies ABSTRACT Davis, Jessica A. M.S., Department of Chemistry, Wright State University, 2012. Synthesis of Mixed Metal Trinuclear Cluster of Molybdenum and Tungsten and Their Electrochemistry in Ionic Liquids Research is being done to find a material to improve the efficiency of the ethanol fuel cell by using a platinum free catalyst. Mo2WO2(O2CCH3)6 cluster was synthesized using Mo2(O2CCH3)4 dimer and Na2WO4. One ionic liquid, EMImBF4, was synthesized using methylimidazolim and chloroethane in the first step, and EMImCl and NaBF4 in the second step. The electrochemical properties of the ionic liquid and the metal cluster were studied. A potential window for the EMImBF4 was found to be 3.2 V. The ionic liquid has a wider potential window, and allowed for the observation of the redox properties of Mo2WO2(O2CCH3)6. The electrochemistry showed that Mo2WO2(O2CCH3)6 cluster can be reduced to metal by reduction at -2.0 V. Finally, Mo2WO2(O2CCH3)6 cluster was deposited onto a platinum electrode. iii TABLE OF CONTENTS PAGE I. INTRODUCTION …………………………………………………………. 1 ALCOHOL FUEL CELL …………………………………………………. 1 METHANOL FUEL CELL ………………………………………………. 3 ETHANOL FUEL CELL …………………………………………………. 4 METAL CLUSTER COMPOUNDS ……………………………………... 6 EARLY TRANSITION METALS ………………………………………... 8 LATE TRANSITION METALS ………………………………………….. 9 TRINUCLEAR METAL CLUSTERS ……………………………………. 9 BINUCLEAR METAL CLUSTERS ……………………………………… 10 TETRANUCLEAR METAL CLUSTERS ………………………………... 12 HEXANUCLEAR METAL CLUSTERS …………………………………. 13 MOLTEN SALTS …………………………………………………………. 13 IONIC LIQUIDS …………………………………………………………... 14 USES OF IONIC LIQUIDS ……………………………………………….. 17 ELECTROCHEMICAL METHODS ……………………………………… 18 iv TABLE OF CONTENTS (CONTINUED) POTENTIMETRY …………………………………………………………. 18 COULOMETRY …………………………………………………………… 18 VOLTAMMETRY ………………………………………………………… 19 CYCLIC VOLTAMMETRY ……………………………………………… 19 II. EXPERIMENTAL ………………………………………………………… 23 MATERIALS ……………………………………………………………... 23 SYNTHESIS OF 1-ETHYL-3-METHYLIMIDAZOLIUM CHLORIDE ... 23 SYNTHESIS OF 1-ETHYL-3-METHYLIMIDAZOLIUM TETRAFLOUROBORATE ……………………………… 24 SYNTHESIS OF Mo2(O2CCH3)4 ................................................................ 26 SYNTHESIS OF [Mo2WO2(O2CCH3)6(H2O)3](CH3SO3H)2 ………….… 26 INSTRUMENTATION ……………………………………………………… 27 III. RESULTS AND DISCUSSION ...………………………………………… 29 SYNTHESIS OF [Mo2WO2(O2CCH3)6(H2O)3](CH3SO3H)2 …………….. 29 SYNTHESIS OF EMImBF4 ……………………………………………. 30 ELECTROCHEMISTRY OF EMImBF4 ………………………………… 31 THE IDENITITY OF Mo2WO2(O2CCH3)6 ……………………………... 33 ELECTROCHEMISTRY OF Mo2WO2(O2CCH3)6 …………………….. 39 v TABLE OF CONTENTS (CONTINUED) IV. CONCLUSION .………………………………………………………… 44 V. REFERENCES …………………………………………………………. 45 vi LIST OF FIGURES FIGURE PAGE 1. Consumption versus production of energy sources in United States …….. 2 2. Major energy consumption source in the U.S. as of 2010 ……………….. 2 3. Methanol fuel cell …………………………...…………………………… 3 4. Ethanol Fuel Cell ……………...………………………………………… 4 4+ 5. Structure of [Mo6Cl8] ………………………………………………….. 7 + 6. Polynuclear complex, Cr3O(CH3CO2)6(H2O)3 ………………………….. 7 2+ 7. Early transition metal, Ta6Cl12 …………………………………………. 8 8. Late transition metal, [Mn2(CO)10] ………………………………………. 9 9. Geometries for trinuclear clusters ……………………………………….. 10 2- 10. Binuclear metal complex, [Re2Cl8] ……………………………………. 11 2- 11. MO diagram for [Re2Cl8] ……………………………………………… 11 12. Geometries of the tetranuclear clusters …………………………………. 12 4+ 13. Hexanuclear cluster, [Mo6Cl8] …….………………………………….. 13 14. Synthesis of ionic liquid, EMImBF4 .…………………………………… 15 15. Common cations used in ionic liquid …………………………………… 16 16. Thermogravimetric analysis for ionic liquids …………………………… 17 17. The three electrodes used in the cell …………………………………….. 20 18. Cyclic voltammetry scan ………………………………………………… 21 19. Reversible and Quasi reversible system …………………………………. 22 vii LIST OF FIGURES (CONTINUED) 20. Titration curve of chloride ion in EMImBF4 with silver nitrate .................. 25 21. Electrochemical cell with working electrode as platinum, reference electrode as Ag | AgCl, and auxillary electrode as platinum ……………………….. 28 22. Structure of Mo2WO2(O2CCH3)6(H2O)3](CH3SO3H)2 cluster ……………. 29 23. Infrared spectrum of EMImBF4 with 600 ppm of H2O …………………. 31 24. EMImBF4 after only one day on high vacuum ………………………….. 32 25. Cyclic voltammogram of EMImBF4 with 600 ppm of H2O …………….. 32 26. Electronic spectra of [Mo2WO2(O2CCH3)6(H2O)3](CH3SO3H)2 dissolved in H2O ………………………………………………………..……………. 33 27. Electronic spectra of [Mo2WO2(O2CCH3)6(H2O)3](CH3SO3H)2 dissolved in EMImBF4 ………………………………………………………………... 34 28. Electronic spectra of Mo3O2(OAc)6(H2O)3(CF3COO)2 in EMImBF4 …… 35 29. Electronic spectra of Mo3O2(OAc)6(H2O)3(CF3COO)2 in EMImBF4 ….... 36 30. NMR spectra for [Mo2WO2(O2CCH3)6(H2O)3](CH3SO3H)2 in D2O ……. 37 31. NMR spectra for Mo3O2(OAc)6(H2O)3(CF3COO)2 in D2O ……………… 38 32. NMR spectra for W3O2(OAc)6(H2O)3(CF3COO)2 in D2O ………………. 38 33. Cyclic voltammogram of Mo2WO2(O2CCH3)6(H2O)3](CH3SO3H)2 dissolved in EMImBF4 …………………………………………………………….. 40 34. Cyclic voltammogram after 24 hours of reduction ……………………… 41 35. Cyclic voltammogram after reduction ……………………………………..42 36. Platinum electrode before and after controlled reduction ……………….. 43 viii LIST OF TABLES TABLE PAGE 1. Reactions in the ethanol fuel ……………………………………………….. 5 2. Thermodynamic data for certain alcohols ………………………………….. 5 3. Bond strengths for transition metals ……………………………………….. 8 4. Cations and anions that can be selected to make ionic liquids ………….... 15 5. Common anions used in ionic liquids ………….…………………………. 16 6. Comparison of electronic spectra of clusters ………………………….…… 37 7. Comparison of NMR spectra of trinuclear clusters ……………………….. 39 ix ACKNOWLEDGEMENT I would like to thank Dr. Vladimir Katovic for the opportunity to join his research group. Thank you for all of your help, support, and guidance throughout this project. You have been a wonderful advisor. I would like to think Kelsi Eberst and Amanda Lock for helping me in the lab. I would like to thank Dr. David Dolson and Dr. David Grossie for helping me through my thesis defense. x DEDICATION To my grandfather, James Abbitt, who teaches me every day the true definition of strength and courage. I read a quote on time and I think it fits you so perfectly: “Be strong. Live honorably and with dignity. When you don't think you can, hold on”. I try to live my life everyday by your example. Your love and guidance has allowed me to become the woman I am today. Thank you for your constant and unfailing love, guidance, and support. I love you more than you will ever know. To my family, thank you for your understanding and support. I could not have gotten through this experience without each and every one of you. I love you all. xi I. INTRODUCTION ALCOHOL FUEL CELL Over the past decade, fuel cells have become a major area of research. Fuel cells are devices that convert chemical energy to electrical energy without the production of a significant amount of heat. The conventional fuels that are used right now are fossil fuels. They are formed through a natural process such as anaerobic decomposition of dead organisms. Fossil fuels take millions of years to form, so they are considered a non- renewable resource. The major use for the fossil fuels right now is as petroleum. The purpose of these fuels is to store energy that can be used at a later time to generate heat or do some form of work. There are many types of alternative fuels that are being used in fuel cells such as: methanol, ethanol, and hydrogen. An alternative fuel source could help