Research Synopsis: Chemistry of reactive intermediates, nuclear spin polarization, electron spin resonance
Heinz D. Roth and his group are interested in organic reaction mechanisms and elucidate structure and reactivity of short-lived free radicals or radical ions in solution or solid matrices. The structures are characterized by optical methods (including diffuse reflectance, DR), magnetic resonance techniques (electron spin resonance, EPR, or chemically induced dynamic nuclear polarization, CIDNP) and molecular orbital calculations. Thermal or photochemical rearrangements of radical ions are investigated by time-resolved electron or nuclear spin polarization or by trapping reactions. Incorporation of donor molecules into redox- or acid-base active zeolites may lead to cyclization, ring-opening or ring contraction.
Electronic structure of radicals
Pictorial representation of the spin density distribution of norcaradiene radical cation (bottom) and its SOMO (center) and LUMO (top) calculated by Spartan.
Molecular model visualizing the docking of 1,2-dithiolane radical cation optimized at the UHF/6-31G* level of theory, inside the straight channels of pentasil zeolite ZSM-5." Research supported by the National Science Foundation".
"Structure and Reactivity of Organic Radical Ions", H. D. Roth, Topics Curr. Chem., 163, 131 - 245 (1992).
"Ring-Opening of Vinylcyclopropane Radical Cations With Stereoselective 1,2-Hydrogen Migration" H. Weng, Q. Sheikh, H. D. Roth, J. Am. Chem. Soc., 1995, 117, 10655-10661.
"Radical Cations of Ethano-Bridged Dicyclopropyl Systems: Remarkable Stereo-electronic Effects" T. Herbertz, H. D. Roth J. Am. Chem. Soc., 1997, 119, 9574-9575.
"Electron Transfer Photochemistry of Chrysanthemyl Alcohol: An Intramolecular SN2' Reaction" T. Herbertz, H. D. Roth, J. Am. Chem. Soc., 1996, 118, 10954-10962.
"Electron Transfer Photochemistry of Tricyclo[4.3.1.01,6]deca-2,4-diene: Nucleophilic Capture of a Homoconjugated Radical Cationic System" T. Herbertz, F. Blume, H. D. Roth J. Am. Chem. Soc. 1998, 120, 4591-4599.
"Electron transfer photochemistry of homo-chrysanthemol: intramolecular nucleophilic attack on the cyclopropane ring" T. Herbertz, H. D. Roth, J. Org. Chem. 1999, 64, 3708-3713.
"Photoreactions of E-1-o-hydroxyphenyl-2-phenylcyclopropane"J. Delgado, A. Espinós, M. C. Jiménez, M. A. Miranda, R. Tormos, H D. Roth, J. Org. Chem. 1999, 64, 6541-6546.
"Oxidative Ring Contraction of 2-Phenyldithiane in ZSM-5: Restricted Mobility of 1,2-Dithiolane Radical Cations in Zeolite Channels" H. D. Roth, K. Shen, P. S. Lakkaraju, L. Fernandez, Chem. Commun. 1998, 2447-2448.
"UV-vis and IR spectroscopic characterization of diphenyl disulfide radical cation in acid zeolites and its rearrangement to thianthrenium radical cation" V. Martí, L. Fernández, V. Fornés, H. García, H. D. Roth, J. Chem. Soc., Perkin Trans. 2 1999,145-152.
"Extended diaryl diselenide radical cations in pentasil zeolite studied by EPR and optical spectroscopy" P. S. Lakkaraju, K. Shen, H. D. Roth, H. García, J. Phys. Chem.A 1999, 103, 7381-7384.
"The Beginnings of Organic Photochemistry", H. D. Roth, Angew. Chem., 1989, 101, 1220-1234; Angew. Chem. Int. Ed. Engl. 1989, 28, 1193-1207.
"A History of Electron Transfer and Related Reactions", H. D. Roth, Topics Curr. Chem. 1990, 156, 1-19.