Niels Damrauer

Research Photochemical Control of Electron-Transfer and Multielectron Chemistry using Shaped Light Fields and Molecular Structure

Research in my group involves a multifaceted approach that combines state of the art physical techniques, synthetic methodologies, and theoretical tools. The chemical questions we ask and answer lie primarily under the umbrella of physical inorganic chemistry with an emphasis on electron-transfer control, solar energy conversion, bioenergetic conversion, photocatalysis, and multielectron chemistry.

One important physical tool that is used – adaptive femtosecond pulse shaping – is a powerful recent development in laser spectroscopy. Its importance stems from the use of an adaptive learning procedure which permits the control and study of complex systems. The starting point of our adaptive control research addresses whether shaped coherent light fields can change active mechanisms of electron transfer in model and biological systems, thus, controlling electron transfer rates, direction, and multi-electron transformations.

The synthetic infrastructure built in our laboratories allows us to ask additional questions of photochemical reaction control that do not rely on the adaptive techniques. One such problem focuses on how excited-state motion in coordination complexes can be utilized to modulate – in a time-dependent fashion – the degree of coupling between an electron donor and an acceptor.

• Sartor, S. M.; Lattke, Y. M.; McCarthy, B. G.; Miyake, G. M.; Damrauer, N. H.; "Effects of Naphthyl Connectivity on the Photophysics of Compact Organic Charge-Transfer Photoredox Catalysts" Journal of Physical Chemistry A 2019, 123, 4727-4736 http://dx.doi.org/10.1021/acs.jpca.9b03286
• Gilligan, A. T.; Miller, E. G.; Sammakia, T.; Damrauer, N. H.; "Using Structurally Well-Defined Norbornyl-Bridged Acene Dimers to Map a Mechanistic Landscape for Correlated Triplet Formation in Singlet Fission" Journal of the American Chemical Society 2019, 141, 5961–5971 http://dx.doi.org/10.1021/jacs.9b00904
• Pearce, O. M.; Duncan, J. S.; Damrauer, N. H.; Dukovic, G.; "Ultrafast Hole Transfer from CdS Quantum Dots to a Water Oxidation Catalyst" The Journal of Physical Chemistry C 2018, 122, 17559-17565 http://dx.doi.org/10.1021/acs.jpcc.8b06237
• Sartor, S. M.; McCarthy, B. G.; Pearson, R. M.; Miyake, G. M.; Damrauer, N. H.; "Exploiting Charge Transfer States for Maximizing Intersystem Crossing Yields in Organic Photoredox Catalysts" Journal of the American Chemical Society 2018, 140, 4778–4781 http://dx.doi.org/10.1021/jacs.8b01001
• McCarthy, B. G.; Pearson, R. M.; Lim, C.-H.; Sartor, S. M.; Damrauer, N. H.; Miyake, G. M. “Structure-Property Relationships for Tailoring Phenoxazines as Reducing Photoredox Catalysts” Journal of the American Chemical Society 2018, 140, 5088–5101. http://dx.doi.org/10.1021/jacs.7b12074
• Carey, T. J.; Miller, E. G.; Gilligan, A. T.; Sammakia, T.; Damrauer, N. H. Modular Synthesis of Rigid Polyacene Dimers for Singlet Fission. Organic Letters 2018, 20, 457-460. http://dx.doi.org/10.1021/acs.orglett.7b03817
• Cook, J. D.; Carey, T. J.; Arias, D. H.; Johnson, J. C.; Damrauer, N. H. Solvent-Controlled Branching of Localized versus Delocalized Singlet Exciton States and Equilibration with Charge Transfer in a Structurally Well-Defined Tetracene Dimer. Journal of Physical Chemistry A 2017, 121, 9229-9242. http://dx.doi.org/10.1021/acs.jpca.7b09458
• Du, Y.; Pearson, R. M.; Lim, C. H.; Sartor, S. M.; Ryan, M. D.; Yang, H.; Damrauer, N. H.; Miyake, G. M. Strongly Reducing, Visible-Light Organic Photoredox Catalysts as Sustainable Alternatives to Precious Metals. Chemistry - A European Journal. 2017, 23, 10962-10968. http://dx.doi.org/10.1002/chem.201702926 
• Carey, T. J.; Snyder, J. L.; Miller, E. G.; Sammakia, T.; Damrauer, N.H. Synthesis of Geometrically Well-Defined Covalent Acene Dimers for Mechanistic Exploration of Singlet Fission. Journal of Organic Chemistry 2017, 82, 4866–4874. http://dx.doi.org/10.1021/acs.joc.7b00602
• Fatur, S. M.; Shepard, S. G.; Higgins, R. F.; Shores, M. P.; Damrauer, N. H. A Synthetically-Tunable System to Control MLCT Excited- State Lifetimes and Spin States in Iron (II) Polypyridines. Journal of the American Chemical Society 2017. http://dx.doi.org/10.1021/jacs.7b00700
• Lim, C.-H.; Ryan, M. D.; McCarthy, B. G.; Theriot, J. C.; Sartor, S. M.; Damrauer, N. H.; Musgrave, C. B.; Miyake, G. M. Intramolecular Charge Transfer and Ion Pairing in N,N-Diaryl Dihydrophenazine Photoredox Catalysts for Efficient Organocatalyzed Atom Transfer Radical Polymerization. Journal of the American Chemical Society 2016. http://dx.doi.org/10.1021/jacs.6b11022
• Cook, J. D., Carey, T. J. & Damrauer, N. H. Solution-Phase Singlet Fission in a Structurally Well-Defined Norbornyl-Bridged Tetracene Dimer. Journal of Physical Chemistry A 2016. http://dx.doi.org/10.1021/acs.jpca.6b04367
• Spettel, K. E.; Damrauer, N. H. Exploiting Conformational Dynamics of Structurally Tuned Aryl-Substituted Terpyridyl Ruthenium(II) Complexes to Inhibit Charge Recombination in Dye-Sensitized Solar Cells. Journal of Physical Chemistry C 2016, 120, 10815–10829. http://dx.doi.org/10.1021/acs.jpcc.6b03302
• Higgins, R. F.; Fatur, S. M.; Shepard, S. G.; Stevenson, S. M.; Boston, D. J.; Ferreira, E. M.; Damrauer, N. H.; Rappé, A. K.; Shores, M. P. Uncovering the Roles of Oxygen in Cr(III) Photoredox Catalysis. Journal of the American Chemical Society 2016, 138, 5451–5464. http://dx.doi.org/10.1021/jacs.6b02723
• Shepard, S. G.; Fatur, S. M.; Rappe, A. K.; Damrauer, N. H. Highly-strained iron(II) polypyridines: exploiting the quintet manifold to extend the lifetime of MLCT excited states. Journal of the American Chemical Society 2016, 138, 2949–2952. http://dx.doi.org/10.1021/jacs.5b13524
• Arias, D. H.; Ryerson, J. L.; Cook, J. D.; Damrauer, N. H.; Johnson, J. C. Polymorphism influences singlet fission rates in tetracene thin films. Chemical Science. 2016, 7, 1185–1191. http://dx.doi.org/10.1039/C5SC03535J
• Miaja-Avila, L.; O’Neil, G.C.; Joe, Y.I.; Alpert, B.K.; Damrauer, N.H.; Doriese, W.B.; Fatur, S.M.; Fowler, J.W.; Hilton, G.C.; Jimenez, R.; Reintsema, C.D.; Schmidt, D.R.; Silverman, K.L.; Swetz, D.S.; Tatsuno, H.; Ullom, J.N. Ultrafast time-resolved hard x-ray emission spectroscopy on a table top. Physical Review X 2016, 6, 031047. https://journals.aps.org/prx/abstract/10.1103/PhysRevX.6.031047
• Damrauer, N. H.; Snyder, J. L. Symmetry-Directed Control of Electronic Coupling for Singlet Fission in Covalent Bis-Acene Dimers. The Journal of Physical Chemistry Letters. 2015, 6, 4456–4462. http://dx.doi.org/10.1021/acs.jpclett.5b02186
• Alguire, E. C.; Subotnik, J. E.; Damrauer, N. H. Exploring Non-Condon Effects in a Covalent Tetracene Dimer: How Important are Vibrations in Determining the Electronic Coupling for Singlet Fission? The Journal of Physical Chemistry A 2014, 119, 299-311. http://dx.doi.org/10.1021/jp510777c 
• Spettel, K. E.; Damrauer, N. H. Synthesis, Electrochemical Characterization, and Photophysical Studies of Structurally Tuned Aryl-Substituted Terpyridyl Ruthenium(II) Complexes. The Journal of Physical Chemistry A. (2014) ASAP. dx.doi.org/10.1021/jp508145w
• Damrauer, R.; Lin, H.; Damrauer, N. H. Computational Studies of Carbodiimide Rings. The Journal of Organic Chemistry  79, 3781-3788 (2014). dx.doi.org/10.1021/jo4026435
• Vallet, P. J.; Snyder, J. L.; Damrauer, N. H. Tunable Electronic Coupling and Driving Force in Structurally Well- Defined Tetracene Dimers for Molecular Singlet Fission: A Computational Exploration Using Density Functional Theory. The Journal of Physical Chemistry A.  117, 10824–10838 (2013). dx.doi.org/10.1021/jp407426q
• Hewitt, J. T.; Concepcion, J. J.; Damrauer, N. H.  Inverse Kinetic Isotope Effect in the Excited-State Relaxation of a Ru(II)−Aquo Complex: Revealing the Impact of Hydrogen-Bond Dynamics on Nonradiative Decay. Journal of the American Chemical Society 135, 12500–12503 (2013). dx.doi.org/10.1021/ja4037498
• Vallet, P. J.; Damrauer, N. H. Experimental and Computational Exploration of Ground and Excited State Properties of Highly Strained Ruthenium Terpyridine Complexes. The Journal of Physical Chemistry A. 117, 6489–6507 (2013). dx.doi.org/10.1021/jp404248z
• Tseng, H. W. Wilker, M. B., Damrauer, N. H., Dukovic, G. Charge Transfer Dynamics between Photoexcited CdS Nanorods and Mononuclear Ru Water-Oxidation Catalysts. Journal of the American Chemical Society 135, 3383–3386 (2013). dx.doi.org/10.1021/ja400178g
• McDaniel, A. M.; Tseng, H. W.; Hill, E. A.; Damrauer, N. H.; Rappé, A. K.; Shores, M. P. Syntheses and Photophysical Investigations of Cr(III) Hexadentate Iminopyridine Complexes and Their Tris(Bidentate) Analogues Inorganic Chemistry 52, 1368-1378 (2013). dx.doi.org/10.1021/ic302055r
• Hewitt, J. T.; Vallet, P. J.; Damrauer, N. H. Dynamics of the 3MLCT in Ru(II) terpyridyl complexes probed by ultrafast spectroscopy: evidence of excited-state equilibration and interligand electron transfer. The Journal of Physical Chemistry A 116, 11536-11547 (2012). dx.doi.org/10.1021/jp308091t
• Grumstrup, E. M.; Damrauer, N. H. Modeling and correction of distorted two-dimensional Fourier transform spectra from pixelated pulse shaping devices. Optics Express 20, 20908 (2012). http://dx.doi.org/10.1364/OE.20.020908
• Vallet, P. J.; Damrauer, N. H. Computational Exploration of Heterolytic Halogen-Carbon Bond Scission Photoreactions in Ruthenium Polypyridyl Complexes (2011) The Journal of Physical Chemistry A. 115, 3122-3132 (2011).
• Grumstrup, E. M.; Johnson, J. C.; Damrauer, N. H. Enhanced Triplet Formation in Polycrystalline Tetracene Films by Femtosecond Optical-Pulse Shaping. Physical Review Letters 105, 257403 (2010).
• Montgomery, M. A.; Grumstrup, E. M.; Damrauer, N. H. Fourier Transform Spectroscopies Derived from Amplitude or Phase Shaping of Broad-Band Laser Pulses with Applications to Adaptive Control. Journal of the Optical Society of America B. 27, 2518-2533 (2010).
• Meylemans, H. A.; Hewitt, J. T.; Abdelhaq, M.; Vallett, P. J.; Damrauer, N. H. Exploiting Conformational Dynamics to Facilitate Formation and Trapping of Electron Transfer Photoproducts in Metal Complexes. Journal of the American Chemical Society 132, 11464–11466 (2010).
• McDaniel, A. M.; Tseng, H. W.; Damrauer, N. H.; Shores, M. P. Synthesis and Solution Phase Characterization of Strongly Photooxidizing Heteroleptic Cr(III) Tris-Dipyridyl Complexes: Toward Efficient Hole Transfer Sensitizers. Inorganic Chemistry 49, 7981-7991 (2010).
• Meylemans, H. A.; Damrauer, N. H. Controlling Electron Transfer through the Manipulation of Structure and Ligand-Based Torsional Motions: A Computational Exploration of Ruthenium Donor-Acceptor Systems using Density Functional. Inorganic Chemistry 48, 11161-11175 (2009).
• Montgomery, M. A.; Damrauer, N. H. A Convenient Method to Simulate and Visually Represent Two-Photon Power Spectra of Arbitrarily Shaped Broadband Laser Pulses. New Journal of Physics (Special Issue on Quantum Control Edited by H. Rabitz) 11, 105053 (2009).
• Meylemans, H. A.; Lei, C.F..; Damrauer, N. H. Ligand Structure, Conformational Dynamics, and Excited-State Electron Delocalization for Control of Photoinduced Electron Transfer Rates in Synthetic Donor–Bridge–Acceptor Systems Inorganic Chemistry 47, 4060-4076 (2008).
• Grumstrup, E. M. ; Shim, S. H.; Montgomery, M. A.; Zanni, M. T.; Damrauer, N. H. Facile Collection of Two-Dimensional Electronic Spectra with Pulse Shaping Technology. Optics Express 15, 16681-16689 (2007).
• Montgomery, M. A.; Meglen, R. R.; Damrauer, N. H. General Method for Reducing Adaptive Laser Pulse Shaping Experiments to a Single Control Variable. J. Phys. Chem. A 111, 5126-5129 (2007).
• Montgomery, M. A.; Damrauer, N. H. Elucidation of Control Mechanisms Discovered During Adaptive Manipulation of [Ru(dpb)3](PF6)2 Emission in the Solution Phase. Journal of Physical Chemistry A. 111, 1426-1433 (2007).
• Montgomery, M. A.; Meglen, R. R.; Damrauer, N. H. Robust Basis Functions for Control from Dimension Reduction of Adaptive Pulse-Shaping Experiments. Ultrafast Phenomena XV, R. J. D. Miller, A. M. Weiner, P. Corkum, and D. M. Jonas, eds., Springer Series in Chemical Physics, Springer, Berlin, (2006).
• Montgomery, M. A.; Meglen, R. R.; Damrauer, N.H. A General Method for the Dimension Reduction of Adaptive Control Experiments. Journal of Physical Chemistry A. 110, 6391-6394 (2006).