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Eman earns a fellowship!

December 21, 2016

The Mindlin Foundation selected Eman for their 2017 Undergraduate Mentored Research Program. The award provides funds for Eman to continue her research into molecular cages all the way through the end of 2017. Congratulations Eman!

Sir Fraser Stoddart wins the Nobel Prize!!

October 5, 2016

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!!!

Welcome Andrew Greenlee, Qifan Xiao, Eman Ahmed, Joe Romo, and Kofi Ofosu

May 16, 2016

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!

Honors for Dan

April 11, 2016

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!

NSF GRFP Honorable Mention for Dan Lee

March 29, 2016

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!

Mohammed Modan starts in the lab

February 1, 2016

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!

Penny Kahn joins the group

November 5, 2015

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!

Combiflash up and running

October 2, 2015

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.

Welcome Dan Lee

September 10, 2015

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.

Birth of a Lab Website

February 17, 2015

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 Cao - the PI

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.

Cao lab pic

Eman Ahmed '18

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.



Penelope Kahn '17

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 Modan '18

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.


Joseph Romo '18

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 Xiao '18

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 (Charles) Ofosu '19

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.


Alkyne Expansion

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.

Our Related Publications

Aromatic Imides

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.

Our Related Publications


A complete list of Dennis' publications.
[28] Visible Light-Driven Artificial Molecular Switch Actuated by Radical–Radical and Donor–Acceptor Interactions (Junling Sun, Yilei Wu, Zhichang Liu, Dennis Cao, Yuping Wang, Chuyang Cheng, Dongyang Chen, Michael R. Wasielewski, J. Fraser Stoddart), In J. Phys. Chem. A, volume 119, 2015. [bibtex] [pdf] [doi]
[27] Heterogeneity of Functional Groups in a Metal–organic Framework Displays Magic Number Ratios (Andrew C.-H. Sue, Ranjan V. Mannige, Hexiang Deng, Dennis Cao, Cheng Wang, Felipe Gándara, J. Fraser Stoddart, Stephen Whitelam, Omar M. Yaghi), In Proc. Nat. Acad. Sci., volume 112, 2015. [bibtex] [pdf] [doi]
[26] Lock-Arm Supramolecular Ordering: A Molecular Construction Set for Cocrystallizing Organic Charge Transfer Complexes (Anthea K. Blackburn, Andrew C.-H. Sue, Alexander K. Shveyd, Dennis Cao, Alok Tayi, Ashwin Narayanan, Brian S. Rolczynski, Jodi M. Szarko, Ozgur A. Bozdemir, Rie Wakabayashi, Jessica A. Lehrman, Bart Kahr, Lin X. Chen, Majed S. Nassar, Samuel I. Stupp, J. Fraser Stoddart), In J. Am. Chem. Soc., volume 136, 2014. [bibtex] [pdf] [doi]
[25] Assembly of Supramolecular Nanotubes from Molecular Triangles and 1,2-Dihalohydrocarbons (Zhichang Liu, Guoliang Liu, Yilei Wu, Dennis Cao, Junling Sun, Severin T. Schneebeli, Majed S. Nassar, Chad A. Mirkin, J. Fraser Stoddart), In J. Am. Chem. Soc., volume 136, 2014. [bibtex] [pdf] [doi]
[24] A Square-Planar Tetracoordinate Oxygen-Containing Ti4O17 Cluster Stabilized by Two 1,1′-Ferrocenedicarboxylato Ligands (Zhichang Liu, Juying Lei, Marco Frasconi, Xiaohu Li, Dennis Cao, Zhixue Zhu, Severin T. Schneebeli, George C. Schatz, J. Fraser Stoddart), In Angew. Chem. Int. Ed., 2014. [bibtex] [pdf] [doi]
[23] Mechanical Bonds and Topological Effects in Radical Dimer Stabilization (Marco Frasconi, Takashi Kikuchi, Dennis Cao, Yilei Wu, Wei-Guang Liu, Scott M. Dyar, Gokhan Barin, Amy A. Sarjeant, Charlotte L. Stern, Raanan Carmieli, Cheng Wang, Michael R. Wasielewski, William A. Goddard, J. Fraser Stoddart), In J. Am. Chem. Soc., 2014. [bibtex] [pdf] [doi]
[22] Two-point Halogen Bonding between 3,6-Dihalopyromellitic Diimides (Dennis Cao, Michael Hong, Anthea K. Blackburn, Zhichang Liu, James M. Holcroft, J. Fraser Stoddart), In Chem. Sci., 2014. [bibtex] [pdf] [doi]
[21] Interface-Engineered Bistable [2]Rotaxane-Graphene Hybrids with Logic Capabilities (Chuancheng Jia, Hao Li, Jiaolong Jiang, Jindong Wang, Hongliang Chen, Dennis Cao, J. Fraser Stoddart, Xuefeng Guo), In Adv. Mater., volume 25, 2013. [bibtex] [pdf] [doi]
[20] Topological Isomerism in a Chiral Handcuff Catenane (Karel J. Hartlieb, Anthea K. Blackburn, Severin T. Schneebeli, Ross S. Forgan, Amy A. Sarjeant, Charlotte L. Stern, Dennis Cao, J. Fraser Stoddart), In Chem. Sci., volume 5, 2013. [bibtex] [pdf] [doi]
[19] Three-Dimensional Architectures Incorporating Stereoregular Donor–Acceptor Stacks (Dennis Cao, Michal Juríček, Zachary J. Brown, Andrew C.-H. Sue, Zhichang Liu, Juying Lei, Anthea K. Blackburn, Sergio Grunder, Amy A. Sarjeant, Ali Coskun, Cheng Wang, Omar K. Farha, Joseph T. Hupp, J. Fraser Stoddart), In Chem. Eur. J., volume 19, 2013. [bibtex] [pdf] [doi]
[18] Selective Isolation of Gold Facilitated by Second-Sphere Coordination with α-Cyclodextrin (Zhichang Liu, Marco Frasconi, Juying Lei, Zachary J. Brown, Zhixue Zhu, Dennis Cao, Julien Iehl, Guoliang Liu, Albert C. Fahrenbach, Youssry Y. Botros, Omar K. Farha, Joseph T. Hupp, Chad A. Mirkin, J. Fraser Stoddart), In Nature Commun., volume 4, 2013. [bibtex] [pdf] [doi]
[17] A Radically Configurable Six-State Compound (Jonathan C. Barnes, Albert C. Fahrenbach, Dennis Cao, Scott M. Dyar, Marco Frasconi, Marc A. Giesener, Diego Benítez, Ekaterina Tkatchouk, Oleksandr Chernyashevskyy, Weon Ho Shin, Hao Li, Srinivasan Sampath, Charlotte L. Stern, Amy A. Sarjeant, Karel J. Hartlieb, Zhichang Liu, Raanan Carmieli, Youssry Y. Botros, Jang Wook Choi, Alexandra M. Z. Slawin, John B. Ketterson, Michael R. Wasielewski, William A. Goddard, J. Fraser Stoddart), In Science, volume 339, 2013. [bibtex] [pdf] [doi]
[16] Size-Selective pH-Operated Megagates on Mesoporous Silica Materials (Min Xue, Dennis Cao, J. Fraser Stoddart, Jeffrey I. Zink), In Nanoscale, volume 4, 2012. [bibtex] [pdf] [doi]
[15] Tetrathiafulvalene Hetero Radical Cation Dimerization in a Redox-Active [2]Catenane (Cheng Wang, Scott M. Dyar, Dennis Cao, Albert C. Fahrenbach, Noah Horwitz, Michael T. Colvin, Raanan Carmieli, Charlotte L. Stern, Sanjeev K. Dey, Michael R. Wasielewski, J. Fraser Stoddart), In J. Am. Chem. Soc., volume 134, 2012. [bibtex] [pdf] [doi]
[14] Radically Enhanced Molecular Switches (Albert C. Fahrenbach, Zhixue Zhu, Dennis Cao, Wei-Guang Liu, Hao Li, Sanjeev K. Dey, Subhadeep Basu, Ali Trabolsi, Youssry Y. Botros, William A. Goddard, J. Fraser Stoddart), In J. Am. Chem. Soc., volume 134, 2012. [bibtex] [pdf] [doi]
[13] Ground-State Thermodynamics of Bistable Redox-Active Donor–Acceptor Mechanically Interlocked Molecules (Albert C. Fahrenbach, Carson J. Bruns, Dennis Cao, J. Fraser Stoddart), In Acc. Chem. Res., volume 45, 2012. [bibtex] [pdf] [doi]
[12] Room-Temperature Ferroelectricity in Supramolecular Networks of Charge-Transfer Complexes (Alok S. Tayi, Alexander K. Shveyd, Andrew C.-H. Sue, Jodi M. Szarko, Brian S. Rolczynski, Dennis Cao, T. Jackson Kennedy, Amy A. Sarjeant, Charlotte L. Stern, Walter F. Paxton, Wei Wu, Sanjeev K. Dey, Albert C. Fahrenbach, Jeffrey R. Guest, Hooman Mohseni, Lin X. Chen, Kang L. Wang, J. Fraser Stoddart, Samuel I. Stupp), In Nature, volume 488, 2012. [bibtex] [pdf] [doi]
[11] The Effects of Conformation on the Noncovalent Bonding Interactions in a Bistable Donor–Acceptor [3]Catenane (Cheng Wang, Dennis Cao, Albert C. Fahrenbach, Sergio Grunder, Sanjeev K. Dey, Amy A. Sarjeant, J. Fraser Stoddart), In Chem. Commun., volume 48, 2012. [bibtex] [pdf] [doi]
[10] A Rigid Donor–Acceptor Daisy Chain Dimer (Dennis Cao, Cheng Wang, Marc A. Giesener, Zhichang Liu, J. Fraser Stoddart), In Chem. Commun., volume 48, 2012. [bibtex] [pdf] [doi]
[9] Stimulated Release of Size-Selected Cargos in Succession from Mesoporous Silica Nanoparticles (Cheng Wang, Zongxi Li, Dennis Cao, Yan-Li Zhao, Justin W. Gaines, O. Altan Bozdemir, Michael W. Ambrogio, Marco Frasconi, Youssry Y. Botros, Jeffrey I. Zink, J. Fraser Stoddart), In Angew. Chem. Int. Ed., volume 51, 2012. [bibtex] [pdf] [doi]
[8] Solvent-Dependent Ground-State Distributions in a Donor–Acceptor Redox-Active Bistable [2]Catenane (Cheng Wang, Dennis Cao, Albert C. Fahrenbach, Lei Fang, Mark A. Olson, Douglas C. Friedman, Subhadeep Basu, Sanjeev K. Dey, Youssry Y. Botros, J. Fraser Stoddart), In J. Phys. Org. Chem., volume 25, 2012. [bibtex] [pdf] [doi]
[7] Donor–Acceptor Ring-in-Ring Complexes (Ross S. Forgan, Cheng Wang, Douglas C. Friedman, Jason M. Spruell, Charlotte L. Stern, Amy A. Sarjeant, Dennis Cao, J. Fraser Stoddart), In Chem. Eur. J., volume 18, 2012. [bibtex] [pdf] [doi]
[6] Novel C3-Symmetric n-Type Tris(aroyleneimidazole) and its Analogs: Synthesis, Physical Properties and Self-Assembly (David Hanifi, Dennis Cao, Liana M. Klivansky, Yi Liu), In Chem. Commun., volume 47, 2011. [bibtex] [pdf] [doi]
[5] Multilayered Nanofibers from Stacks of Single-Molecular Thick Nanosheets of Hexakis(alkoxy)triphenylenes (Gayane Koshkakaryan, Peng Jiang, Virginia Altoe, Dennis Cao, Liana M. Klivansky, Yue Zhang, Sungwook Chung, Allard Katan, Florent Martin, Miquel Salmeron, Biwu Ma, Shaul Aloni, Yi Liu), In Chem. Commun., volume 46, 2010. [bibtex] [pdf] [doi]
[4] Dual Selectivity Expressed in [2 + 2 + 1] Dynamic Clipping of Unsymmetrical [2]Catenanes (Gayane Koshkakaryan, Dennis Cao, Liana M. Klivansky, Simon J. Teat, Jasper L. Tran, Yi Liu), In Org. Lett., volume 12, 2010. [bibtex] [pdf] [doi]
[3] Probing Donor−Acceptor Interactions and Co-Conformational Changes in Redox Active Desymmetrized [2]Catenanes (Dennis Cao, Matteo Amelia, Liana M. Klivansky, Gayane Koshkakaryan, Saeed I. Khan, Monica Semeraro, Serena Silvi, Margherita Venturi, Alberto Credi, Yi Liu), In J. Am. Chem. Soc., volume 132, 2010. [bibtex] [pdf] [doi]
[2] Alternative Donor−Acceptor Stacks from Crown Ethers and Naphthalene Diimide Derivatives: Rapid, Selective Formation from Solution and Solid State Grinding (Gayane Koshkakaryan, Liana M. Klivansky, Dennis Cao, Marian Snauko, Simon J. Teat, Jochem O. Struppe, Yi Liu), In J. Am. Chem. Soc., volume 131, 2009. [bibtex] [pdf] [doi]
[1] Linear π-Acceptor-Templated Dynamic Clipping to Macrobicycles and [2]Rotaxanes (Liana M. Klivansky, Gayane Koshkakaryan, Dennis Cao, Yi Liu), In Angew. Chem. Int. Ed., volume 48, 2009. [bibtex] [pdf] [doi]

Dennis Cao

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' Graduate/Postdoctoral Work

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 [2]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).

Dennis' Undergraduate Work

Dennis spent two years conducting undergraduate research and learning the art of organic synthesis in the gorgeous Molecular Foundry at Lawrence Berkeley National Laboratory in Dr. Yi Liu's Group. The highlights of his first research experience are described below.


Multistate Molecular Switches. Dennis' first undergraduate research project entailed the synthesis of [2]catenanes containing four different aromatic stations that are all electrochemically active. Some of the [2]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 [2]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 [2]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).


*Honors Thesis †NSF Honorable Mention  


Time in Group


Current Whereabouts

Daniel Lee*† 2015-2016 Lots and lots of driving. PhD Student at the University of Minnesota
Andrew Greenlee 2016 Lots of reaction tubes in one oil bath. Student at Macalester


Dennis D. Cao

Department of Chemistry Macalester College 1600 Grand Avenue Saint Paul, MN 55105, USA Email: dcao at macalester.edu Tel: +1-651-696-6593