Tien-Sung Tom Lin
We have employed both cw and pulsed EPR techniques to study the structure and dynamics of paramagnetic species: reactive intermediates, such as free radicals; photo-induced paramagnetism, such as photo-excited triplet state; transition metal containing compounds and enzymes. Below are two areas of our current interests.
Applications of zero-field (ZF) EPR spectroscopy. Recently, we developed a field and frequency agile pulsed EPR spectrometer to measure the properties and dynamics of photo-excited triplet state of organic molecules in ZF and low magnetic field. The conventional wisdom regards the first order hyperfine interaction (HFI) between electron and nuclear spin is zero in ZF because the magnetic moment is negligible in ZF. We have demonstrated the HFI can be observed in ZF during the pulsed EPR FID detection period for the photo-excited triplet state of organic molecules after the application of a short microwave pulse. The measurements in ZF and near ZF (0.1 - 1.0 mT) show that organic molecules remember the events happen shortly before \the measurements. The molecular memory and associated selective spin population in the photo-excitation could render organic solids a new class of materials for quantum computing. We have observed the drastic changes of spectral profile when we turn on a magnetic field as small as 0.4 mT by a field jump technique. We believe this is a promising experimental technique to examine a particular interaction, such as hyperfine, quadrupole, or other types of interactions by imposing a selective external field during the FID period. The technique allows us to examine the natural line width, spin-spin relaxation, dynamic nuclear polarization, and phase transition induced by molecular motions (Fig. 1).
Chemistry in the confined space of mesoporous silica (MPS) materials. We have studied the catalytic reactions and reaction pathways of enzymes and biomimetic model compounds immobilized in the nanochannels of MSP materials (pore diameter of 2 - 10 nm) by spectroscopic techniques: Uv-Visible, IR, EPR and NMR. These reactions are carried out in the nanopores (nanoreactors), which effectively make the concentration much higher and avoid the random attacks between fast-reacting species. Nanoreactors therefore open up the possibility of "single molecule chemistry" otherwise accessible only in extreme dilution. The nanopores of MPS provide proper environment, electrostatic attraction, geometry and configuration, to facilitate catalytic reactions, increase the stability of catalytic centers, and yield high turnover number (Fig. 2). Site-isolation of native enzymes and biomimetic complexes through encapsulation in porous solid materials further allow the use of less sterically demanding ligands while retains structural stability (Fig. 3).
L. L. Dugan, D. M. Turetsky, C. Du, D. Lobner, M. Wheeler, R. Almli, C. K.-F.Shen, T.-Y. Luh, D. W. Choi, and T.-S. Lin, "Carboxyfullernes as Neuroprotective Agents", Proc. Natl. Acad. Sci., 94, 9434 -9439 (1997).
Jun Lang, David J. Sloop, and Tien-Sung Lin, "Dynamics of p-terphenyl crystals at the phase transition temperature: A zero-field EPR study of the photo-excited triplet state of pentacene in p-terphenyl crystals" J. Phys. Chem. - A, 111, 4731- 4736 (2007).
Tomoaki Yago, Tien-Sung Lin, Gerhard Link, and Gerd Kothe, "Pulsed Electron Nuclear Double Resonance Studies of the Photo-excited Triplet State of Pentacene in p-Terphenyl Crystals at Room Temperature" J. Chem. Phys. 127, 114503 ( 2007).
Chia-Hung Lee, Tien-Sung Lin, and Chung-Yuan Mou, "Mesoporous Materials for Encapsulating Enzymes" Nano Today 4, 165-179 (2009).
Chia-Hung Lee, Han-Chou Lin, Tien-Sung Lin, and Chung-Yuan Mou, "Reactivity Study of Hydroxo-Bridged Dinuclear Cupric Complexes Encapsulated in Mesoporous Silica: Model Compounds for Catechol Oxidases", J. Phys. Chem. - C 113, 16058-16069 (2009).
Kun-Che Kao, Chia-Hung Lee, Tien-Sung Lin, and Chung-Yuan Mou, "Cytochrome c covalently immobilized on mesoporous silicas as a peroxidase: Orientation effect", J. Mater. Chem. 20, 4653 - 4662 (2010).
Gerd Kothe, Tomoaki Yago, Jörg-Ulrich Weidner, Gerhard Link, Michail Lukaschek, and Tien-Sung Lin, "Quantum Oscillations of Nuclear Spins in Photo-excited Triplet States", J. Phys. Chem. B, 114, 14755-14762 (2010).
Ya-Cheng Fang, Chia-Hung Lee, I-Jui Hsu, Tien-Sung Lin, and Chung-Yuan Mou, “Bio-inspired Design of a Cu-Zn-Imidazolate Mesoporous Silica Catalyst System for Superoxide Dismutation”, J. Phys. Chem. C, 115, 20639-20652 (2011).
Amolkumar Karwa, Amruta R. Poreddy, Bethel Asmelash, Tien-Sung Lin, Richard B. Dorshow, and Raghavan Rajagopalan, “Type I Phototherapeutic Agents Part 1: Preparation and Cancer Cell Viability Studies of Novel Photolabile Thiaza Compounds”, ACS Medicinal Chemistry Letters, 2, 828 – 833 (2011).
Raghavan Rajagopalan, Tien-Sung Lin, Amolkumar S. Karwa, Amruta R. Poreddy, Bethel Asmelash, and Richard B. Dorshow, “Type 1 Phototherapeutic Agents, Part II: Cancer Cell Viability and ESR Studies of Tricyclic Diarylamines”, ACS Medicinal Chemistry Letters, 3, 284-288 (2012).
Xiaoyan Liu, Ming-Han Liu, Yi-Chia Luo, Chung-Yuan Mou, Shawn Lin, Hong Cheng, Jin-Ming Chen, Jyh-Fu Lee, Tien-Sung Lin, “Strong metal-support interactions between gold nanoparticles and ZnO nanorods in CO oxidation”, JACS (accepted for publication, 2012).
1985-present, Professor, Department of Chemistry, Washington University
1996-present, Professor of Neurology, School of Medicine, Washington University
1976-1985, Associate Professor, Department of Chemistry, Washington University
1970-1976, Assistant Professor, Department of Chemistry, Washington University
2006 May-June, 2005 March-April, Visiting Professor, Department of Chemistry, University of Frieburg, Germany
1997-2008 Summers, Visiting Professor, Department of Chemistry, National Taiwan University, Taiwan
1998, 1999, 2000 (16 months), Visiting Professor, Institute of Physical and Chemical Research, Japan (under Eminent Scientist Program)
1993-1996 Summers, Visiting Professor, Institute of Atomic and Molecular Sciences, Academia Sinica, Taiwan
1989-1990, Visiting Professor, Huygens Laboratory (Physics), University of Leiden, The Netherlands
1981-1981, Scientist-in-Residence, Chemistry Division, Argonne National Laboratory, Illinois
Chemistry 115, General Chemistry Laboratory I
Chemistry 116, General Chemistry Laboratory II
Chemsitry 401, Physical Chemistry I
Chemistry 402, Physical Chemistry II
Chemistry 445, Instrumental Method: Physical Chemistry Laboratory
Chemistry 571, Quantum Chemistry and Spectra
Chemistry 5762, Electron Spin Resonance
Chemistry 584, Molecular Spectroscopy