Dennis' PhD advisor, Fraser Stoddart, was awarded the Nobel Prize in Chemistry for his work on molecular machines and switches. Dennis is grateful to have played a part in the Stoddart group, and hopes that his work was at least 0.0001% responsible for the Prize. Congratulations Fraser!!!
It'll be a busy 10 weeks of summer with 6 students in the lab. Andrew, Qifan, Eman, and Joe are rising junior chemistry majors, and Kofi is a rising sophomore who intends to be a major as well. They will all be synthesizing crazy molecules, characterizing their properties, and generally having a wild time. These opportunities were made possible through generous awards by the MacKnight Haan Ludwig Summer Research Fund (Andrew and Qifan), Violet Olson Beltmann Fund (Eman and Mohammed), and Science and Research Office Funds (Joe and Kofi). Welcome everyone!
Dan presented and successfully defended his Honors Project after an appropriate grilling by a friendly committee. We look forward to seeing his thesis on our shelves soon!
This year's NSF Graduate Research Fellowship Program applicant field had over 17000 applicants, many of whom are current graduate students. We're proud that Dan was recognized among so many other qualified candidates. Congratulations Dan!
Our group continues to expand! Mohammed is a sophomore chemistry major who got into research by computationally evaluating his organic chemistry professor's conformational analysis abilities. Mohammed will be attempting to synthesize some novel aromatic imides that he has been modeling over the last semester. Welcome Mohammed!
The group keeps on growing with the addition of Penny Kahn! Penny is a biology major and anthropology/chemistry minor in her junior year and she is excited to be enhancing her chemical skillset in preparation for a future career in research. Penny will be developing new reactions for the synthesis of aromatic imides. Welcome Penny!
A new Combfilash Rf+ is up running in the Cao lab! This automated chromatography instrument will hopefully lead to exponential increases in the productivity of the group.
The group is doubling in size with the arrival of Dan Lee! Dan is a senior undergraduate who is participating in the Macalester Honors Program for the 2015-2016 academic year. As part of the Honors Program, Dan will be synthesizing novel structures using alkyne metathesis. Dan comes to the group with previous summer research experiences at UIUC in Kami Hull's lab as an REU Scholar, and at Caltech in Robert Grubbs' lab as an Amgen Scholar.
Dennis begins his independent career at Macalester officially on August 1, 2015. In the meantime, he has excitedly spent some time creating this rudimentary website. Hopefully it will be filled with interesting news updates as the years go on.
Dennis was born in Konstanz, Germany and grew up in San Diego, California. He began his education at UC Berkeley in 2006 and did his undergrad research with Dr. Yi Liu at Lawrence Berkeley National Laboratory. In 2010, Dennis found his way into grad school and Prof. J. Fraser Stoddart's lab at Northwestern where he crystallized metal-organic frameworks and organic ferroelectrics before graduating in June 2014. He then did a postdoctoral stint in Prof. Samuel I. Stupp’s group, working on self-assembling materials. Dennis' independent career at Macalester College began in August 2015. Scroll further down for more details about his research experiences. Outside of chemistry, Dennis tries to balance his lifestyle with passions for photography, travel, Houston Rockets basketball, and a various random hobbies.
Eman is from Karachi, Pakistan. She is a rising junior, Chemistry major and Biology minor. She developed her interest for research after working in Dr. Marcos Ortega’s lab last summer, where she purified protein gpA, which is involved in the insertion of the viral DNA into a procapsid. After taking organic chemistry at Macalester, she developed an interest in the synthesis of molecules, since it allows her to challenge herself. She is excited to be a part of the Cao lab where she will be working on assembling organic cages. Outside of Chemistry, Eman enjoys eating desserts, travelling, exercising and shopping.
Andrew Greenlee is from Studio City, California. Though this is his first research opportunity, since he began studying organic photovoltaics in his first year of chemistry he looked forward to the opportunity to apply his theoretical knowledge in a laboratory setting. As a chemistry major with a biochemistry emphasis and a music minor, he is considering a career in the healthcare industry, though he is also entertaining the notion of a career in chemistry as it relates to environmental sustainability. In his free time, he enjoys jazz bass, distance running, Game of Thrones, and painting toenails.
Penny is from Atlanta, Georgia. She is a junior Biology major with minors in Chemistry and Anthropology. Penny got an early start on research in high school during the Summer of 2012 when she worked in Dr. Eric Gaucher’s group at Georgia Institute of Technology, investigating the biological role of fluorescent proteins in corals. The subsequent semester she worked in the same group as a lab assistant to Ryan Randall on her research on constructing an experimental phylogeny by mutating red fluorescent proteins in order to create a benchmark for computational methods of ancestral sequence reconstruction. Besides research, Penny enjoys crossword puzzles, painting, and traveling.
Mohammed is from Marin County, California. He is a Chemistry major with an emphasis in Biochemistry. Although this is his first research experience, he is excited to apply what he has learned from years of chemistry in the classroom to make discoveries in the lab. He began this research with a focus on computational chemistry, marrying the subject with his love of technology. As for the future, Mohammed is considering a career in healthcare, either as a physician, or in a related science such as medicinal chemistry. Outside of chemistry and technology, Mohammed enjoys hiking/camping, trail running, slacklining, and posting pictures of Joe.
Joe is from Long Island, New York. He is a sophomore Chemistry major with Added Emphasis in Biochemistry. Joe’s interest in research started early on during his high school career. Under the guidance of Dr. Michael Vaccariello, Joe investigated the effects of artificial sweeteners on Drosophila melanogaster. His work led him to receive the notable Principal’s Award of Excellence in Scientific Research for four consecutive years. Joe is excited to be a part of the Cao Lab and is currently studying photocatalysis of water splitting. Outside of the lab, Joe enjoys fishing, traveling, photography, and watching New York Yankees baseball.
Qifan is from Chengdu, China. He is a sophomore Chemistry major. Qifan’s passion for chemistry started with the copper sulfate solution he found in his “Little Chemist's Kit” birthday gift. He got a glimpse of real chemistry world in the summer of 2015 when he worked in Professor Xia’s group in Nuclear Chemistry Laboratory at Sichuan University, focusing on the grafting of graphite oxide to synthesize porous materials. He is excited to join the Cao Lab and to work on novel compounds, and is looking forward to become a chemical engineer in the future. Besides chemistry, Qifan likes chess, classical guitar, travelling and exploring restaurants.
Kofi is a rising sophomore at Macalester College who comes from Ghana. He has not yet declared his major, but as of now, he is working towards a chemistry major with an added emphasis in biochemistry. He loves chemistry, so much so that in high school, as part of the requirement for the International Baccalaureate program, he chose to write an extended essay (a 4000 word paper) in Chemistry, where he explored the effects of concentration and ionic size on the conductivity of electrolytic solutions. Outside class, he enjoys playing soccer, going for long walks, and cooking. He also like to sing as part of the Macalester African Music Ensemble.
We are interested in producing 2D and 3D alkyne-expanded derivatives of known hydrocarbon compounds. We hypothesize that a thoughtful molecular design, in conjunction with alkyne metathesis reactions, will lead us to compounds with interesting porosities and other unexpected features.
We are targeting novel compounds that consist of aromatic cores with multiple imide groups appended to them, similar to the known mellitic triimide (right). We hypothesize that steric constraints may lead to interesting radical electron properties in the reduced states of the proposed molecules.
|||Visible Light-Driven Artificial Molecular Switch Actuated by Radical–Radical and Donor–Acceptor Interactions , In J. Phys. Chem. A, volume 119, 2015.|
|||Heterogeneity of Functional Groups in a Metal–organic Framework Displays Magic Number Ratios , In Proc. Nat. Acad. Sci., volume 112, 2015.|
|||Lock-Arm Supramolecular Ordering: A Molecular Construction Set for Cocrystallizing Organic Charge Transfer Complexes , In J. Am. Chem. Soc., volume 136, 2014.|
|||Assembly of Supramolecular Nanotubes from Molecular Triangles and 1,2-Dihalohydrocarbons , In J. Am. Chem. Soc., volume 136, 2014.|
|||A Square-Planar Tetracoordinate Oxygen-Containing Ti4O17 Cluster Stabilized by Two 1,1′-Ferrocenedicarboxylato Ligands , In Angew. Chem. Int. Ed., 2014.|
|||Mechanical Bonds and Topological Effects in Radical Dimer Stabilization , In J. Am. Chem. Soc., 2014.|
|||Two-point Halogen Bonding between 3,6-Dihalopyromellitic Diimides , In Chem. Sci., 2014.|
|||Interface-Engineered Bistable Rotaxane-Graphene Hybrids with Logic Capabilities , In Adv. Mater., volume 25, 2013.|
|||Topological Isomerism in a Chiral Handcuff Catenane , In Chem. Sci., volume 5, 2013.|
|||Three-Dimensional Architectures Incorporating Stereoregular Donor–Acceptor Stacks , In Chem. Eur. J., volume 19, 2013.|
|||Selective Isolation of Gold Facilitated by Second-Sphere Coordination with α-Cyclodextrin , In Nature Commun., volume 4, 2013.|
|||A Radically Configurable Six-State Compound , In Science, volume 339, 2013.|
|||Size-Selective pH-Operated Megagates on Mesoporous Silica Materials , In Nanoscale, volume 4, 2012.|
|||Tetrathiafulvalene Hetero Radical Cation Dimerization in a Redox-Active Catenane , In J. Am. Chem. Soc., volume 134, 2012.|
|||Radically Enhanced Molecular Switches , In J. Am. Chem. Soc., volume 134, 2012.|
|||Ground-State Thermodynamics of Bistable Redox-Active Donor–Acceptor Mechanically Interlocked Molecules , In Acc. Chem. Res., volume 45, 2012.|
|||Room-Temperature Ferroelectricity in Supramolecular Networks of Charge-Transfer Complexes , In Nature, volume 488, 2012.|
|||The Effects of Conformation on the Noncovalent Bonding Interactions in a Bistable Donor–Acceptor Catenane , In Chem. Commun., volume 48, 2012.|
|||A Rigid Donor–Acceptor Daisy Chain Dimer , In Chem. Commun., volume 48, 2012.|
|||Stimulated Release of Size-Selected Cargos in Succession from Mesoporous Silica Nanoparticles , In Angew. Chem. Int. Ed., volume 51, 2012.|
|||Solvent-Dependent Ground-State Distributions in a Donor–Acceptor Redox-Active Bistable Catenane , In J. Phys. Org. Chem., volume 25, 2012.|
|||Donor–Acceptor Ring-in-Ring Complexes , In Chem. Eur. J., volume 18, 2012.|
|||Novel C3-Symmetric n-Type Tris(aroyleneimidazole) and its Analogs: Synthesis, Physical Properties and Self-Assembly , In Chem. Commun., volume 47, 2011.|
|||Multilayered Nanofibers from Stacks of Single-Molecular Thick Nanosheets of Hexakis(alkoxy)triphenylenes , In Chem. Commun., volume 46, 2010.|
|||Dual Selectivity Expressed in [2 + 2 + 1] Dynamic Clipping of Unsymmetrical Catenanes , In Org. Lett., volume 12, 2010.|
|||Probing Donor−Acceptor Interactions and Co-Conformational Changes in Redox Active Desymmetrized Catenanes , In J. Am. Chem. Soc., volume 132, 2010.|
|||Alternative Donor−Acceptor Stacks from Crown Ethers and Naphthalene Diimide Derivatives: Rapid, Selective Formation from Solution and Solid State Grinding , In J. Am. Chem. Soc., volume 131, 2009.|
|||Linear π-Acceptor-Templated Dynamic Clipping to Macrobicycles and Rotaxanes , In Angew. Chem. Int. Ed., volume 48, 2009.|
Haven't heard enough about this Dennis Cao guy yet? His CV can be found here (updated November 18, 2015). Read on for more enthralling information about his graduate and undergraduate research experiences.
Dennis did his graduate studies in Professor J. Fraser Stoddart's Group at Northwestern University. After graduating, he moved two buildings away to do a postdoctoral internship in Professor Samuel I. Stupp's Group. Some of the more significant projects Dennis worked on during this time are highlighted below.
Halogen Bonding. This project is the product of the hard work of Michael Hong, an undergraduate that Dennis mentored. Together they synthesized halogenated pyromellitic diimides and demonstrated that they form two-point halogen-oxygen bonding interactions in the solid state (Chem. Sci. 2014, 4242−4248).
Organic Ferroelectrics. In collaboration with Ashwin Narayanan in Professor Samuel I. Stupp's Group at Northwestern University, Dennis helped to develop the lock-arm supramolecular ordering (LASO) paradigm, which is a general molecular design strategy for amplifying the crystallization of charge transfer complexes that revolves around the synergistic action of hydrogen bonding and charge transfer interactions. Some of the robust single crystalline materials display ferroelectric hysteresis at room temperature (Nature 2012, 488, 485) and ongoing structural modifications to the component molecules have yielded LASO crystals with significantly improved materials properties.
Metal-Organic Frameworks. Dennis worked on integrating mechanically interlocked molecules into metal-organic frameworks (MOFs) with the aim of creating robust arrays of molecular switches. Along the way, it became apparent that the π-electron rich and π-electron faces of the catenane struts altered the self-assembly process of the final crystalline product. These noncovalent bonding interactions were exploited to generate syndiotactic layers of 2D MOFs (Chem. Eur. J. 2013, 19, 8457) and assemble a two-component MOF with a magic number ratio of components that is independent of the molar proportions present in the crystallization medium (PNAS 2014, 112, 5591).
Multistate Molecular Switches. Dennis' first undergraduate research project entailed the synthesis of catenanes containing four different aromatic stations that are all electrochemically active. Some of the catenanes exhibited reversible electrochemical switching between six different states (J. Am. Chem. Soc. 2010, 132, 1110).
Dynamic Covalent Chemistry. Working with another undergraduate student, Gayane Koshkarayan, Dennis demonstrated that a linear dumbbell-shaped bipyridinium molecule can template cage formation around itself through sixfold imine bond formation to give an interlocked rotaxane as the single product (Angew. Chem. Int. Ed. 2009, 48, 4185). This highly efficient [2+3] clipping occurs despite the symmetry mismatch between the template and the formed macrobicycle. An analogous [2+2] clipping reaction can be employed to synthesize dynamic catenanes (Org. Lett. 2010, 12, 1528).
Discotic Molecules. Dennis' final project involved the synthesis and purification of tris(aroyleneimidazole) derivatives. He was fortunate enough to isolate pure compound during his last week in Berkeley. These molecules exhibit desirable bandgaps, broad absorptions, high thermal stabilities, and tend to self-assemble into fibers (Chem. Commun. 2011, 47, 3454).
Time in Group
|Daniel Lee*†||2015-2016||Lots and lots of driving.||PhD Student at the University of Minnesota|