Dept. of Chemistry

Andrew G. Tennyson

Photo of Andy TennysonAssistant Professor
Inorganic Chemistry

Phone: (864) 656-3158
Office: 483 Hunter Laboratories
E-mail: atennys@clemson.edu

Research Interests | Publications

EDUCATION & TRAINING

Dr. Tennyson received his S.B. with Honors in chemistry and S.M. in inorganic chemistry from the University of Chicago in 2003. He earned his Ph.D. in bioinorganic chemistry from the Massachusetts Institute of Technology in 2008 and was a postdoctoral fellow in organic & organometallic chemistry at the University of Texas at Austin from 2008-2010. Dr. Tennyson joined Clemson University in 2010 as an Assistant Professor in the Department of Chemistry and the Center for Optical Materials Science and Engineering Technologies (COMSET), and in 2012 he received a joint appointment in the Department of Materials Science and Engineering.

RESEARCH INTERESTS

1.         Multidrug Resistant Infectious Diseases

            Increasingly drug-resistant diseases pose an significant threat to public health and safety.  Tuberculosis (TB), for example, has been causing disease and death in humans for nearly 5 millennia.  By the 19th century, TB was responsible for almost one-fourth of all deaths in Europe.  Development of streptomycin in 1946 significantly decreased its incidence and mortality rate, but recent TB strains are no longer affected by this treatment.  The objective of this research is to develop compounds that will be effective against diseases that are resistant to all front-line drugs.  We hypothesize that organometallic complexes will be effective against multidrug resistant diseases such as TB and methicillin-resistant stapholycoccus aureus.

2.         Detection of Proto-Inflammatory Biomolecules

            Reperfusion injury due to stroke is a leading cause of mental disability among adults in the US.  During a stroke, loss of oxygen supply to affected tissues (ischemia) causes cells therein to begin dying.  Restoration of oxygen-carrying blood supply, however, brings with it a flood of reactive oxygen species (compounds with oxygen-centered radicals), which causes cell death and can lead to tissue/organ failure.  This reperfusion injury ultimately produces damage more significant and more widespread than the initial ischemia.  Whereas ischemia causes immediate, permanent damage, reperfusion injury is gradual and can be mitigated or even reversed up to 72 h after the stroke.  The objective of this research is to develop imaging agents that can reveal damaging reactive oxygen species in biological systems, in a reversible manner, so that it can indicate when these species have been eliminated.  We hypothesize that ferrocene-based compounds can be designed to be water-soluble, oxidize reversibly under conditions relevant to reperfusion injury, and exhibit measurable near-infrared fluorescence responses. 

3.         Charge Pair Dissociation and Recombination in Organic Semiconductors

            3.1       Generating Persistent Electric Fields in Organic Photovoltaic Cells

            Inefficient charge separation is a major energy loss pathway in organic photovoltaic (OPV) cells and fundamentally limits the power-conversion efficiency (PCE) of these devices.  In a typical OPV cell, a photogenerated exciton is converted at a donor–acceptor interface to a Coulombically-bound electron–hole charge pair, which can then be dissociated by an electric field to produce usable current.  Under maximum power generating conditions, however, the majority of charge pairs cannot dissociate and therefore do not contribute to current.  Near-total (> 90%) charge pair dissociation would require a field > 50 MV/m, but a typical OPV cell cannot produce more than 3 MV/m without an external bias.  Electric fields of this magnitude that persist with no external bias can be realized with ferroelectric materials, which can be polarized by an applied field and remain polarized after its removal.  The objective of this research is to develop OPV cells in which persistent electric fields can be induced using ferroelectric nanoparticles.  We hypothesize that these fields will facilitate charge pair dissociation in OPV cells and produce a transformational advance in the PCEs achievable by these devices.

4.         Bilayer Interfaces and Monophase Composites

            4.1       Reducing Series Resistance in Organic Photovoltaic Cells

            Contact resistance at the junction of dissimilar materials is a major contributor to series resistance (RS) in organic photovoltaic (OPV) cells, thus fundamentally constraining power-conversion efficiency (PCE).  Usable current from an OPV cell depends on the separation of electrons and holes, which can be achieved with organic semiconducting materials (OSMs).  At an electrode–OSM junction, passive diffusion of electrons and holes into the p- and n-type materials, respectively, depletes mobile charges from the interface and generates a Schottky barrier that opposes further charge diffusion.  Inserting a charge-transporting material (CTM) between the electrode and OSM layers eliminates this Schottky barrier, enhancing charge transport and PCE.  However, many CTMs are electronically and structurally dissimilar with OSMs, where this mismatch causes contact resistance and phase separation, potentially negating any gains in PCE.  The objective of this research is to develop electron/hole transporting materials that provide minimal contact resistance with the OSM layer in OPV cells.  We hypothesize that common donor polymers partially loaded with charged substituents will exhibit reduced contact resistance with their neutral counterparts and increased electron/hole transport in OPV cells, thus affording significant gains in PCE.

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SELECTED PUBLICATIONS

10. Laughlin, B. J.; Baker, W. F.; Duniho, T. L.; El Homsi, S. J.; Tennyson, A. G.; Smith, R. C.; “Synthesis, Photophysical and Electrochemical Properties of Conjugated Polymers Incorporating 9,9-Dialkyl-1,4-Fluorenylene Units with Thiophene, Carbazole and Triarylamine Comonomers” Polym. Chem. 2012, 3, 3318–3323.

9. He, S.; Buelt, A. A.; Hanley, J. M.; Morgan, B. P.; Tennyson, A. G.; Smith, R. C.; “Sterically encumbered bipyridyl-derivatized conjugated polymers and metallopolymers incorporating phenylenevinylene, phenyleneethynylene and fluorenylene segments” Macromolecules 2012, 45, 6344–6352.

8. Tennyson, A. G.; Lippard, S. J.; “Generation, Translocation, and Action of Nitric Oxide in Living Systems” Chem. Biol. 2011, 18, 1211–1220.

7. Tennyson, A. G.; Wiggins, K. M.; Bielawski, C. W.; “Mechanical Activation of Catalysts for C–C Bond Forming and Anionic Polymerization Reactions from a Single Macromolecular Reagent” J. Am. Chem. Soc. 2010, 132, 16631–16636.

6. Tennyson, A. G.; Norris, B. C.; Bielawski, C. W.; “Structurally Dynamic Conjugated Polymers.” Macromolecules 2010, 43, 6923–6935. (Cover Feature)

5. Tennyson, A. G.; Lynch, V. M.; Bielawski, C. W.; “Arrested Catalysis: Controlling Kumada Coupling Activity via a Redox-Active N-Heterocyclic Carbene.” J. Am. Chem. Soc. 2010, 132, 9420–9429.

4. Tennyson, A. G.; Rosen, E. L.; Collins, M. S.; Lynch, V. M.; Bielawski, C. W.; “Bimetallic N-Heterocyclic Carbene–Iridium Complexes: Investigating Metal-Metal and Metal-Ligand Communication via Electrochemistry and Phosphorescence Spectroscopy.” Inorg. Chem. 2009, 48, 6924–6933.

3. Tennyson, A. G.; Kamplain, J. W.; Bielawski, C. W.; “Oxidation of poly(enetetraamine)s: A new synthetic strategy for conjugated polyelectrolytes.” Chem. Commun. 2009, 2124–2126.

2. Tennyson, A. G.; Dhar, S.; Lippard, S. J.; “Synthesis and Characterization of {Ni(NO)}10 and {Co(NO)2}10 Complexes Supported by Thiolate Ligands” J. Am. Chem. Soc. 2008, 130, 15087–15098.

1. Tennyson, A. G.; Smith, R. C.; Lippard, S. J.; “Selective Fluorescence Detection of Nitroxyl over Nitric Oxide in Buffered Aqueous Solution using a Conjugated Metallopolymer” Polyhedron 2007,4625–4630.

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