Randolph P. Thummel

Randolph P. Thummel
John & Rebecca Moores Professor
	Office: 123d Fleming Phone: (713) 743-2734 Email: thummel@uh.edu Education B.S., Brown University, 1967 Ph.D., University of California, Santa Barbara, 1971 Honors, Fellowships, etc. NIH Postdoctoral Fellow, Ohio State University, 1971-73 Fulbright Senior Research Scholar, 1990-91 Enron Teaching Excellence Award, 2000 UH Award for Excellence in Research, 2005 Homepage

Research Interests

Organic and Inorganic Chemistry

     Our main interest is the design and synthesis of novel ligand systems. Ligands, in the broadest sense, are species which interact with other species through the formation of non-covalent bonds: metal-ligand complexes are one good example. In that context, we have prepared a wide variety of derivatives of 2,2'-bipyridine, 2,2';6,2"-terpyridine and 1,10-phenanthroline (see 3D x-rays on homepage). In many cases we have used polymethylene bridging to control the conformation of the ligand as in the diphenanthrolines 1. The related terphenanthroline forms a helical trinuclear complex with Cu(I) which resembles the coiling of DNA (Figure 1). Aza-aromatic rings can be arranged in a parallel fashion to provide rigid syn-orthocyclophanes that complex two metals in a layered orientation. We have prepared chiral steroidal phenanthrolines such as 2 as well as a trans-chelating bipyridine analogue 3.

     Cavity shaped molecules possessing indole subunits can accept neutral organic guests by taking advantage of a well organized hydrogen-bonding assembly as shown by structure 4. Hosts of this type show excellent potential for binding a variety of biologically important molecules such as amides and ureas. Bridged bithiazolium and biimidazolium salts undergo the reversible transfer of one or two electrons to provide radical cations or neutral species such as 5. The redox properties and donor-acceptor abilities of these species can be tuned by varying the length of their polymethylene bridges.
     More recently we have become interested in using ligand design for the chemical utilization of solar energy. We are developing a combinatorial approach to the synthesis of new photosensitizers for semi-conductor based solar cells. We have also synthesized a new family of ruthenium catalysts that very efficiently convert water into dioxygen. Attempts are underway to make this process photocatalytic, leading to a practical system for solar water decomposition.

Figure 1. Trinuclear Cu(I)
complex of terphenanthroline.
Figure 2. A dinuclear Ru(II) catalyst
which can efficiently oxidize water.

Recent Publications

"Detection and Structural Characterization of Clusters with Ultrashort-Lived Electronically Excited States: IR Absorption Detected by Femtosecond Multiphoton Ionization," Nosenko, Y.; Kuniski, M.; Thummel, R. P.; Kyrychenko, A.; Herbich, J.; Waluk, J.; Riehn, C.; Brutschy, B. J. Am. Chem. Soc. 2006, 128, 10000-10001.

"7-Pyridylindoles: Synthesis, Structure, and Properties," Mudadu, M. S.; Singh, A.; Thummel, R. P. J. Org. Chem. 2006, 71, 7611-7617.

"Synthetic Approaches to Polypyridyl Bridging Ligands with Proximal Multidentate Binding Sites," Zong, R.; Wang, D.; Hammitt, R.; Thummel, R. P. J. Org. Chem. 2006, 71, 1676-175.

"Photosensitizers Containing the 1,8-Naphthyridyl Moiety and their Use in Dye Sensitized Solar Cells," Kukrek, A.; Wang, D.; Hou, Y.; Zong, R.; Thummel, R. Inorg. Chem. 2006, 45, 10131-T10137.

"Excited State Proton Transfer in 2,9-(Di-2’-pyridyl)-4,7-di(t-butyl)carbazole," Wiosna-Salyga, G.; Dobkowski, J.; Mudadu, M. S.; Sazanovich, I.; Thummel, R. P.; Waluk, J. Chem. Phys. Lett. 2006, 423, 288-292.

"[1,10]-Phenanthrolin-2-yl Ketones and their Coordination Chemistry," Bark, T. G.; Thummel, R. P. Inorg. Chem. 2005, 44, 8733-8739.

"2,2’;9’,2"-Terphenanthroline," Zong, R.; Thummel, R. P. Inorg. Chem. 2005, 44, 5984-5986.

"Ruthenium(II) Complexes of 1,12-Diazaperylene and their Interactions with DNA," Chouai, A.; Wicke, S.; Turro, C.; Bacsa, J.; Dunbar, K.; Thummel, R. P. Inorg. Chem. 2005, 44, 5996-6003.

"A New Family of Ru Complexes for Water Oxidation," Zong, R.; Thummel, R. P. J. Am. Chem. Soc. 2005, 127, 12802-12803.

"Enhanced Luminescence in a Pt(II) Complex Involving a Six-Membered Chelate Ring" Y.-Z. Hu, M. H. Wilson, R. Zong, C. Bonnefous, D. R. McMillin, and R. P. Thummel, JCS Dalton Trans. 2005, 354-358.

"The Design and Study of Bi[1,8]-naphthyridine Ligands as Potential Photooxidation Mediators in Ru(II) Polypyridyl Aqua Complexes" R. Zong, F. Naud, C. Segal, J. Burke, F. Wu, and R. Thummel, Inorg. Chem. 2004, 43, 6195-6202.

"Ru(II) Complexes of Di-[1,10]-phenanthrolinyl Diazines" D. Brown, R. Zong and R. P. Thummel, Eur. J. Inorg. Chem. 2004, 3269-3272.

"2,9-Di-(2'-pyridyl)-1,10-phenanthroline: a Tetradentate Ligand for Ru(II)" R. Zong and R. P. Thummel, J. Am. Chem. Soc. 2004, 126, 10800.

"The Preparation and Study of Di-(2-quinolyl)- and Di(2-[1,8]naphthyridyl)- Derivatives of Pyrimidine and Pyrazine as Bridging Ligands for Ru(II)," Brown, D.; Muranjan, S.; Thummel, R. P. Eur. J. Inorg. Chem. 2003, 3547.

"A Friedländer Approach for the Incorporation of 6-Bromoquinoline into Novel Chelating Ligands," Hu, Y.-Z.; Zhang, G.; Thummel, R. P. Organic Letters 2003, 5, 2251.

"Cu(I) Complexes of 3,3'-Polymethylene Bridged Derivatives of 2,2'-Bi-1,10-Phenan-throline," Riesgo, E. C.; Hu, Y.-Z.; Thummel, R. P. Inorg. Chem. 2003, 42, 6648-6654.

"Pyrene-Bridged Bis-phenanthroline Ligands and their Dinuclear Ruthenium(II) Complexes," Chouai, L.; Wu, F.; Jang, Y.; Thummel, R. P. Eur. J. Org. Chem. 2003, 2774.

"Bi-1,10-phenanthrolines and Their Mono-nuclear Ru(II) Complexes," Hu, Y.-Z.; Xiang, Q.; Thummel, R. P. Inorg. Chem. 2002, 41, 3423.

"Chiral 2,2'-Bipyridines, 1,10-Phenanthrolines and 2,2':6,2"-Terpyridines: Syntheses and Applications in Asymmetric Homogeneous Catalysis," Chelucci, G.; Thummel, R. P. Chem. Revs. 2002, 102, 3129.

"Di-[1,10]-phenanthrolinyl Diazines: A New Family of Bis-tridentate Chelators," Brown, D.; Muranjan, S.; Y. Jang, Y.; Thummel, R. Org. Lett. 2002, 4, 1253.

"A Unique 2:1 Complex with a trans-Chelating Bis-pyridine Ligand," Hu, Y.-Z.; Chamchoumis, C.; Grebowicz, J. S.; Thummel, R. P. Inorganic Chem. 2002, 41, 2296.

"Ru(II) Complexes of Crowded Delocalized Diimine Ligands," Wu, F.; Thummel, R. P. Inorg. Chim. Acta 2002, 327, 26

"Fluorescence Quenching by Pyridine and Derivatives Induced by Intermolecular Hydrogen Bonding to Pyrrole Containing Heteroaromatics," Herbich, J; Kijak, M.; Zielinska, A,; Thummel, R. P.; Waluk, J. J. Phys. Chem. 2002, 106, 2158.

"Cyclometallated Complexes of Ru(II) with 2-Aryl-1,10-phenanthrolines," Bonnefous, C.; Thummel, R. P. Inorganic Chem. 2001, 40, 5851.

"Crowded Cu(I) Complexes Involving Benzo[h]quinoline: p-Stacking Effects and Long Lived Luminescent Excited States," Riesgo, E.; Bouvier, F.; Thummel, R. P.; Scaltrito, D.; Meyer, G. J. Inorganic Chem. 2001, 40, 3413.

"Evaluation of Diimine Ligand Exchange on Cu(I)," Bouvier, F.; Riesgo, E.; Thummel, R. P. Inorganic Chem. 2001, 40, 2541.

"Friedländer Synthesis of Chiral Alkyl-Substituted1,10-Phenanthrolines," Gladiali, S.; Chelucci, G.; Mudadu, M. S.; Thummel, R. P. J. Org. Chem. 2001, 66, 400.

"A Strong Enhancement of the Lanthanide-Centred Luminescence in Complexes with 4-Alkylated 2,2';6,2"-Terpyridines," Mürner, H.-R.; Chassat, E.; Thummel, R. P.; Bünzli, J.-C. G. J. Chem. Soc. Dalton Trans. 2000, 2809.

"Bidentate Ligands which Contain Pyrrole in Place of Pyridine," F. Wu, C. Chamchoumis, R. P. Thummel, Inorganic Chemistry 2000, 39, 584.

"Mono and Dinuclear Ru(II) and Os(II) Polypyridine Complexes Built Around Spiro-bridged Bis-phenanthroline ligands :Synthesis, Electrochemistry and Photophysics," A. Juris, L. Prodi, A. Harriman, R. Ziessel, M. Hissler, A. El-ghayoury, E. C. Riesgo and R. P. Thummel, Inorganic Chemistry 2000, 39, 3590.

"Solvent-induced Syn-anti Rota-merization of 2-(2'-Pyridyl)indole and the Structure of its Alcohol Complexes," A. Kyrychenko, J. Herbich, F. Wu, R. P. Thummel and J. Waluk, J. Am. Chem. Soc. 2000, 122, 2818.

"Self Assembly of a Diphenanthro- linylpyrene-bridged Cu(I) Trimer," C. Bonnefous, N. Bellec and R. P. Thummel, J. Chem. Soc., Chem. Commun. 1999, 1243.

"Ru(II) Complexes of 2-Aryl-1,10-Phenanthrolines: Synthesis, Structure, and Photophysical Properties," F. Wu, E. C. Riesgo, A. Pavalova, R. A. Kipp, R. Schmehl and R. P. Thummel, Inorganic Chemistry 1999, 38, 5620.

"Role of Ground State Structure in Photoinduced Tautomerization in Bifunctional Proton Donor-acceptor Molecules: 1H-Pyrrolo[3,2-h]quinoline and Related Compounds," A. Kyrychenko, J. Herbich, M. Izydorzak, F. Wu, R. P. Thummel, and J. Waluk, J. Am. Chem. Soc. 1999, 121, 11179.