Background:
- Postdoctoral Scholar, University of California, Los Angeles, 2001-2004
Molecular Switches
Molecular switches offer solutions to nanotechnologies and at their most fundamental level involve control over molecular motions. By investigating redox-active supramolecular motifs, I intend to develop in my research group, the building blocks behind switching systems that have applications ranging from molecular electronics to mechanical engineered systems.
Relevant Disciplines
Physical Organic / Inorganic / Physical / Analytical / Materials
Related Areas
Inorganic Chemistry - Nanoscience - Materials - Spectroscopy and Electrochemistry - Supramolecular Chemistry - Interfacial Science
1. Redox Active Molecular Wires from Mixed-Valency
This research addresses the needs of the microelectronics community to extend Moore's Law. Mixed-valent (MV) coordination compounds (Figure 1) that have delocalized systems will be targeted. Such molecules are attractive systems to transfer from solution to devices in a systematic manner based on (1) structure-property relationships and (2) structurally-sensitive spectroscopy. One component of this research relies upon the development of synthetic methods to functionalize ligands with thiol-based "alligator clips". Secondly, solution-phase Raman spectra will be used to show how the molecular wires behave under bias (+/-) employing self-assembled monolayers (SAMs) as stepping-stones to devices. Their electronic and spectroscopic behavior will be characterized in half devices.
This is funded by the NSF NER program.
2. Molecular Muscles and Non-Innocent Ligands: We have developed redox-active ligands that can serve as switches to the investigation of mechanical motion at the molecular level. Attention is focused on the Cu(I) as a labile transition metal coupled with non-innocent bridging ligands. The thermodynamics and kinetics of the switching will be quantified. We intend to broaden the diversity of ligand-based switching to other metals and extend the complexity of what can be achieved using catenates and rotaxanes that can perform a range of functions -- such as molecular muscles.
3. Sensing Aromatic Analytes with Surface-Enhanced Resonance Raman Spectroscopy (SERRS).
New developments with nanopatterns have made progress towards reproducible surface-enhanced Raman spectroscopy (SERS, Figure 3) using electromagnetic enhancement. However, fundamental challenges remain including, how to tune molecular chromophores to couple the plasmons of patterned surfaces. Insight gained from these studies will allow for quantitative studies of the numbers and identities of molecules on surfaces - laying the foundation for sensing. 
4. Anion Recognition and Click Chemistry . We have developed a novel shape-persistent macrocycle (see image below) that is easily constructed using click chemistry and displays a high affinity for anions. This is one of the first three examples of the weak CH...anion hydrogen bond (the weakest among Nature's cohort) to be reported and therefore represents an iconoclastic breakthrough in the design of anion receptors. Consequently, the extreme modularity provided by the click chemistry as well as the high affinity (some approaching Ka values of 1,000,000 M-1) open up a new and uncharted realm of opportunities. Our goals are to sequester toxic anions from the environment, deliver them to safe locations and, by using our knowledge of molecular machines, to release them into captivity using a photo-driven light switch.
Relevant Publications
- MOLECULAR ELECTRONICS:
Whence Molecular Electronics? (97 citations)
Flood, A. H.; Stoddart, J. F.; Steuerman, D. W.; Heath, J. R., Science 2004, 306, 2055-2056.
- MOLECULAR MACHINES:
Utilizing a non-innocent ligand to enable Cu(I) supramolecular machines to operate by reduction
McNitt, K. A.; Parimal, K.; Fahrenbach, A. C., Flood, A. H., 2008 submitted ;
Can Terdentate 2,6-Bis(1,2,3-Triazol-4-yl)Pyridines form Stable Coordination Compounds?
Li, Y.; Huffman, J. C.; Flood, A. H. Chem. Commun. 2007, 2692-2694.;
Linear Artificial Molecular Muscles (91 citations)
Liu, Y., Flood, A. H. Bonvallet, P. A.; Vignon A. S.; Northrup, B.; Tseng. H.-R.; Jeppesen, J. O.; Huang, T. J.; Brough, B.; Baller, M.; Magonov, S.; Solares, S.; Goddard, W. A.; Ho, C.-M.; Stoddart, J. F., J. Am. Chem. Soc. 2005, 127, 9745-9759;
Meccano on the Nanoscale - A Blueprint for making Some of the World's Tiniest Machines (>100 citations)
Flood, A. H.; Ramirez, R. J. A.; Deng, W.-Q.; Muller, R. P.; Goddard, W. A.; Stoddart, J. F., Aust. J. Chem. 2004, 57, 301-322.
- RAMAN SPECTROSCOPY:
Revealing the Chromophoric Composition of Multichromophoric Polypyridyl Complexes of Re(I) and Os(II): A Resonance Raman Study
Flood, A.; Girling, R.; Hester, R.; Moore, J.; Gordon, K. C.; Polson, M. I. J., J. Raman Spectrosc. 2002, 33, 434-442.
- ANION RECOGNITION:
Pure CH hydrogen bonding to chloride ions: A pre-organized and rigid macrocyclic receptor
Li, Y.; Flood, A. H., Angew. Chem. Int. Ed. 2008, Early View .
Selected Publications:
2008
Li, Y.; Flood, A. H., "Pure CH hydrogen bonding to chloride ions: A pre-organized and rigid macrocyclic receptor," Angew. Chem. Int. Ed. 2008, online Early View .
2007
Saha, S.; Flood, A. H.; Stoddart, J. F.; Impellizzeri, S.; Silvi, S.; Venturi, M.; Credi, A., "A redox-driven multicomponent molecular shuttle," J. Am. Chem. Soc. 2007, 129, 12159-12171.
Ikeda, T.; Saha, S.; Aprahamian, I.; Leung, K. C.-F.; Williams, A.; Deng, W. Q.; Flood, A.H.; Goddard, W. A.; Stoddart, J.F., "Toward electrochemically controllable tristable three-station [2]catenanes," Chem. Asian J. 2007, 2, 76-93.
Nygaard, S.; Laursen, B. W.; Hansen, T. S.; Bond, A. D.; Flood, A. H.; Jeppesen, J. O., "Preparation of cyclobis(paraquat- p -phenylene)-based [2]rotaxanes without flexible glycol chains", Angew. Chem. Int. Ed. 2007, 46, 6093-6097.
Nygaard, S.; Hansen, S. W.; Huffman, J. C.; Jensen, F.; Flood, A. H.; Jeppesen, J. O. "Two Classes of Alongside Charge-Transfer Interactions Defined in One [2]Catenane," J. Am. Chem. Soc. 2007, 129, 7354-7363.
Li, Y.; Huffman, J. C.; Flood, A. H. "Can Terdentate 2,6-Bis(1,2,3-Triazol-4-yl)Pyridines form Stable Coordination Compounds?" Chem. Commun. 2007, 2692-2694.
Nygaard, S.; Liu, Y.; Stein, P. C.; Flood, A. H.; Jeppesen, J. O. "Using Molecular Force to Overcome Steric Barriers in a Spring-Like Molecular Ouroborous," Adv. Funct. Mat. 2007, 17, 751-762.
Nygaard, S.; Leung, K. C.-F.; Aprahamian, I.; Ikeda, T.; Saha, S.; Laursen, B. W.; Kim, S.-Y.; Hansen, S. W.; Stein, P. C.; Flood, A. H.; Stoddart, J. F.; Jeppesen, J. O., "Functionally Rigid Bistable [2]Rotaxanes," J. Am. Chem. Soc. 2007, 129, 960-970.
Bunker, B. C.; Huber, D. L.; Kushmerick, J. G.; Dunbar, T.; Kelly, M.; Matzke, C.; Cao, J.; Jeppesen, J. O.; Perkins, J.; Flood, A. H.; Stoddart, J. F. "Switching Surface Chemistry with Supramolecular Machines," Langmuir 2007, 23, 31-34.
Flood, A. H.; McAdam, C. J.; Gordon, K. C.; Kjaergaard, H. G.; Manning, A. M.; Robinson, B. H.; Simpson, J. "Electronic Stucture and Near-IR Transitions of FcC2R and FcC4R Dyads," Polyhedron 2007, 26, 448-455.
2006
Nygaard, S.; Flood, A. H.; Jeppesen, J. O.; Bond, A. D. " Cis - and Trans -Bis(2-cyanoethylsulfanyl)(decane-1,10-diyldithio)Tetrathiafulvalene," Acta. Cryst. C 2006, 62, 677-680.
Leung, K. C. F.; Mendes, P. M.; Magonov, S. N.; Northrop, B. H.; Kim, S.; Patel, K.; Flood, A. H.; Tseng, H.-R.; Stoddart, J. F. "Supramolecular Self-Assembly of Dendronized Polymers: Reversible Control of the Polymer Architectures through Acid-Base Reactions" J. Am. Chem. Soc. 2006, 129, 10707-10715.
Huang, T.-J.; Flood, A. H.; Brough, B.; Liu, Y.; Bonvallet, P. A.; Kang, S.; Chu, C.-W.; Guo, T.-Z.; Lu, W.; Yang, Y.; Stoddart, J. F.; Ho, C.-H., "Understanding and Harnessing Biomimetic Molecular Machines for NEMS Actuation Materials," IEEE Transactions on Automation Science and Engineering 2006, 3, 254-259.
Arico, F.; Badjic, J. D.; Cantrill, S. J.; Flood, A. H.; Leung, K. C. F.; Liu, Y.; Stoddart J. F. "Templated Synthesis of Interlocked Molecules," in Templates in Chemistry Top. Curr. Chem. Eds: Dötz, F. Vogtle, K. Schalley, Springer Verlag, 2006, 249, 203-259.
Flood, A. H.; Nygaard, S.; Laursen, B. W.; Hansen, C.; Jeppesen, J. O.; Stoddart, J. F., "Locking Down the Electronic Structure of (Monopyrrolo)tetrathiafulvalene in [2]Rotaxanes," Org. Lett. 2006, 8, 2205-2208.
Moonen, N. N. P.; Flood, A. H,; Fernandez, J. M.; Stoddart, J. F., "Towards a Rational Design of Molecular Switches and Sensors from their Basic Building Blocks," Top. Curr. Chem. 2006, 262, 99-132.
Balzani, V.; Clemente-León, M.; Credi, A.; Ferrer, B.; Venturi, M.; Flood, A. H.; Stoddart J. F., "An Autonomous Artificial Nanomotor Powered by Sunlight," Proc. Natl. Acad. Sci. U.S.A. 2006, 103, 1178-1183.
Flood, A. H.; Wong, E. W.; Stoddart, J. F., "Models of charge transport and transfer in molecular switch tunnel junctions of bistable catenanes and rotaxanes" Chem. Phys. 2006, 324, 280-290. (Special Issue dedicated to Professor Noel S Hush, February 28, 2006)
Nygaard, S.; Laursen, B. W.; Flood, A. H; Hansen, C.; Jeppesen, J. O.; Stoddart, J. F., "Quantifying the Working Stroke of Tetrathiafulvalene Based Electrochemically Driven Linear Motor-Molecules," Chem. Commun. 2006, 144-146.
Choi, J. W.; Flood, A. H.; Steuerman, D. W.; Nygaard, S.; Braunschweig, A.; Moonen, N. N. P.; Laursen, B. W.; Luo, Y.; DeIonno, E.; Peters, A. J.; Jeppesen, J. O.; Xu, K.; Stoddart, J. F.; Heath, J. R., "Ground State Equilibrium Thermodynamics and Switching Kinetics of Bistable [2]Rotaxane Switched in Solution, Polymer Gels, and Molecular Electronic Devices," Chem. Eur. J. 2006, 12, 261-279.
2005
Jang, S. S.; Jang, Y. H.; Kim, Y.-H.; Goddard, W. A.; Choi, J. W.; Heath, J. R.; Laursen, B. W.; Flood, A. H.; Stoddart, J. F., "Molecular Dynamics Simulation of Amphiphilic Bistable [2]Rotaxane Langmuir Monolayer at Air/Water Interface," J. Am. Chem. Soc. 2005, 127, 14804-14816.
Huang, T.-J.; Liu, Liu, Y.; Brough, B.; Flood, A,. H.; Bonvallet, P. A.; Tseng, H.-R.; Baller, M.; Magonov, S.; Stoddart, J. F.; Ho, C.-H. "A nano-chemo-mechanical actuator based on artificial molecular machines," Tech. Dig. - IEEE Int. Conf. Micro Electro Mech. Syst., 18th, 2005, 871-874.
Liu, Y.; Saha, S.; Vignon, S. A.; Flood, A. H.; Stoddart, J. F., "Template-Directed Syntheses of Configurable and Reconfigurable Molecular Switches," Synthesis-Stuttgart 2005, 3437-3445.
Norgaard, K.; Laursen, B. W.; Nygaard, S.; Kjaer, K.; Tseng, H.-R.; Flood, A. H.; Stoddart, J. F.; Bjornholm, T., "Structural Evidence for Redox-Controlled Mechanical Switching in Condensed Monolayers of Amphiphilic Bistable Rotaxane Molecules," Angew Chem. Int. Ed. 2005, 44, 7035-7039.
Garaudée, S.; Silvi, S.; Venturi, M.; Credi, A.; Flood, A. H.; Stoddart, J. F., "Shuttling Dynamics in an Acid-Base-Switchable [2]Rotaxane", ChemPhysChem 2005, 6, 2145-2152.
Saha, S.; Johanson, L. E.; Flood, A. H.; Bonvallet, P.; Tseng, H.-R.; Shen, C.; Rubin, Y.; Zink, J. I.; Stoddart, J. F., "A Nanoscale Power Supply Utilizing a Photoactive Molecular Triad to Generate a Photo-Voltage and Operate a Supramolecular Machine," Chem. Eur. J. 2005, 11, 6846-6858.
Nguyen, T; Tseng, H.-R.; Celestre, P. C.; Flood, A. H.; Liu, Y.; Zink, J. I.; Stoddart, J. F. "A Reversible Molecular Valve" Proc. Natl. Acad. Sci. USA 2005, 102, 10029-10034.
Liu, Y., Flood, A. H. Bonvallet, P. A.; Vignon A. S.; Northrup, B.; Tseng. H.-R.; Jeppesen, J. O.; Huang, T. J.; Brough, B.; Baller, M.; Magonov, S.; Solares, S.; Goddard, W. A.; Ho, C.-M.; Stoddart, J. F., "Linear Artificial Molecular Muscles," J. Am. Chem. Soc. 2005, 127, 9745-9759.
Deng, W.-Q.; Flood, A. H.; Stoddart, J. F.; Goddard III, W. A., "Electronic Paper Display Based on a Tristable [2]Catenane," J. Am. Chem. Soc. 2005, 127, 15994-15995.
Howell, S. L.; Scott, S. M.; Flood, A. H.; Gordon, K. C., "The Effect of Reduction on Rhenium(I) Complexes with Binaphthyridine and Biquinoline Ligands: A Spectroscopic and Computational Study," J. Phys. Chem. A 2005, 109, 3745-3753.
Mendes, P. M.; Flood, A. H.; Stoddart, J. F., "Molecular Electronic Devices from Langmuir-Blodgett Monolayers" Appl. Phys. A, 2005, 80, 1197-1209.
Saha, S.; Johanson, L. E.; Flood, A. H.; Tseng, H.-R.; Zink, J. I.; Stoddart, J. F. "Powering a Supramolecular Machine with a Photoactive Molecular Triad," Small 2005, 1, 87-90.
Jang, S. S.; Jang, Y.H.; Kim. Y.-H.; Goddard, W. A.; Flood, A. H.; Laursen, B. W.; Tseng, H.-R.; Stoddart, J. F.; Jeppesen, J. O.; Choi, J. W.; Steuerman, D. W.; DeIonno, E.; Heath, J. R., "Self-Assembled Monolayer of the Heath-Stoddart Type Bistable [2]Rotaxane on Au(111) Surface: Molecular Dynamics Simulation Approach," J. Am. Chem. Soc. 2005 127, 1563-1575.
Liu, Y.; Muscovitz, R.; Flood, A. H.; Stoddart, J. F. Chem. Eur. J. 2005, 11, 369-385.
2004
Flood, A. H.; Stoddart, J. F.; Steuerman, D. W.; Heath, J. R., "Whence Molecular Electronics" Science 2004, 306, 2055-2056.
Flood, A. H.; Peters, A. J.; Vignon, S. A.; Steuerman, D. W.; Tseng, H.-R.; Kang, S.; Heath, J. R.; Stoddart, J. F., "The Role of Physical Environment on Molecular Electromechanical Switching", Chem. Eur. J. 2004, 10, 6558-6561.
Steuerman, D. W.; Tseng, H.-R.; Peters, A. J.; Flood, A. H.; Jeppesen, J. O.; Nielsen, K. A.; Stoddart, J. F.; Heath, J. R., "Molecular Mechanical Switch-Based Solid-State Electrochromic Devices" Angew Chem. Int. Ed . 2004, 43, 6486-6491.
Huang, T. J.; Brough, B.; Ho, C.-M.; Liu, Y.; Flood A, H.; Bonvallet, P.; Tseng, H.-R.; Stoddart, J. F.; Baller, M.; Magonov, S., "From Artificial Molecular Motors to Functional Nanomechanical Devices," Appl. Phys. Lett. 2004, 85, 5391-5393.
Huang, T. J.; Tseng, H.-R.; Sha, L.; Lu, W.; Brough, B.; Flood, A. H.; Yu, B.-D.; Celestre, P. C.; Chang, J. P.; Stoddart, J. F.; Ho, C.-M. "Mechanical Shuttling of Linear Motor-Molecules in Condensed Phases on Solid Substrates," Nano Lett. 2004, 4, 2065-2071.
Lee, I. C.; Frank, C. W.; Yamamoto, T.; Tseng, H.-R.; Flood, A. H.; Stoddart, J. F.; Jeppesen, J. O., "Langmuir and Langmuir-Blodgett Films of Amphiphilic Bistable Rotaxanes," Langmuir 2004, 20, 5809-5828.
Liu, Y.; Flood, A. H.; Stoddart, J. F., "Thermally- and Electrochemically-Controllable Self-Complexing Molecular Switches," J. Am. Chem. Soc. 2004, 126, 9150-9151.
Polson, M. I. J.; Howell, S. L.; Flood, A. H.; Burrell, A. K.; Blackman, A. G.; Gordon, K. C., "Synthesis and Electronic Properties of Mononuclear Osmium(II) and Rhenium(I) Complexes Containing Ligands Derived from [2,3-a:3',2'-c]dipyridophenazine (ppb)," Polyhedron 2004, 23, 1427-1439.
Flood, A. H.; Ramirez, R. J. A.; Deng, W.-Q.; Muller, R. P.; Goddard, W. A.; Stoddart, J. F., "Meccano on the Nanoscale - A Blueprint for making Some of the World's Tiniest Machines," Aust. J. Chem. 2004, 57, 301-322.
2003
Morgan, J. L.; Flood, A. H.; Gordon, K. C.; Robinson, B. H.; Simpson, J., "Rhenium Carbonyl Complexes of 2,6-Diazaanthracene-9,10-dione(daad): Spectroelectrochemistry of BrRe(CO)(4)daad," J. Organomet. Chem. 2003, 675, 57-64.
Morgan, J. L.; Flood, A.; Gordon, K. C.; Kjaergaard, H. G.; Robinson, B. H.; Simpson, J., "2,6-Diazaanthracene-9,10-dione and its Radical Anion-A Structural and Spectroscopic Investigation," Aust. J. Chem. 2003, 56, 607-614.
2002
Sherbourne, J. R.; Page, S. E.; Flood, A.; Polson, M. I. J.; Gordon, K. C., "Resonance Raman Spectroelectrochemistry, using a Raman OTTLE Cell, of Molybdenum Tetracarbonyl Complexes with Polypyridine Ligands," Asian J. Spectros. 2002, 6, 169-177.
Gordon, K. C.; Burrell, A. K.; Simpson, T. J.; Page, S. E.; Kelso, G.; Polson, M. I. J.; Flood, A., "Probing the Nature of the Redox Products and Lowest Excited State of [(bpy)2Ru( m -bptz)Ru(bpy)2]4+: A Resonance Raman Study," Eur. J. Inorg. Chem. 2002, 554-563.
Page, S. E.; Flood, A.; Gordon, K. C., "Electron Localisation in Electrochemically Reduced Mono- and Bi-Nuclear Rhenium(I) Complexes with Bridged Polypyridyl Ligands," J. Chem. Soc., Dalton Trans. 2002, 1180-1187.
Matthewson, B. J.; Flood, A.; Polson, M. I. J.; Armstrong, C.; Phillips, D. L.; Gordon, K. C., "Vibrational Spectra of Dipyrido[3,2-a : 2 ',3 '-c]phenazine and its Radical Anion Analyzed by Ab Initio Calculations and Deuteration Studies," Bull. Chem. Soc. Japan 2002, 75, 933-942.
Flood, A.; Girling, R.; Hester, R.; Moore, J.; Gordon, K. C.; Polson, M. I. J., "Revealing the Chromophoric Composition of Multichromophoric Polypyridyl Complexes of Re(I) and Os(II): A Resonance Raman Study," J. Raman Spectrosc. 2002, 33, 434-442.
2000
Waterland, M. R.; Flood, A.; Gordon, K. C., "Metal-to-Ligand Charge-Transfer Excited-States in Binuclear Copper(I) Complexes. Tuning MLCT Excited-States through Structural Modification of Bridging Ligands. A Resonance Raman Study," J. Chem. Soc., Dalton Trans. 2000, 2, 121-127.
Babaei, A.; Brooksby, P. A.; Flood, A.; McQuillan, A. J., "ATR Infrared Spectroelectrochemistry of the Reduction Products of Anthraquinonesulfonates in Aqueous Solutions," Appl. Spectrosc. 2000, 54, 496-501.
