How different metals stick together

Editor: Tamara Hanna JEM: Esther RTP: Bryan Nolte

Cover artwork from Inorganic Chemistry featuring paper from the Thomas group

Metal-metal interactions are at the heart of some of the most interesting metal-catalyzed transformations and are found everywhere from Nature (metalloenzymes) to industrially important heterogeneous catalysis (surfaces, nanomaterials).  While textbooks have been written about metal-metal multiple bonds, surprising gaps in knowledge remain, including bonding between first row transition metals and bonding between different metals.  The Thomas group in the Brandeis Chemistry Department seeks to fill these gaps in knowledge through the systematic synthesis of heterobimetallic complexes featuring a wide range of different transition metals and developing a thorough understanding of the electronic structure and bonding of these novel compounds.

The latest issue of Inorganic Chemistry features cover artwork highlighting the recent paper from the Thomas laboratory titled “Exploring Trends in Metal–Metal Bonding, Spectroscopic Properties, and Conformational Flexibility in a Series of Heterobimetallic Ti/M and V/M Complexes (M = Fe, Co, Ni, and Cu).” The paper describes an extensive study of a series of Ti/M and V/M heterobimetallic complexes, where M is systematically varied across the periodic table from left to right (Fe, Co, Ni, Cu).  These complexes are classified as “early/late” heterobimetallic complexes because they feature one metal from the left half of the periodic table (“early”) and one metal from the right half of the periodic table (“late”).  The inherent differences between the properties of the two metals makes their metal-metal bonding quite polar and sensitive to a variety of different factors, but also poises these compounds for interesting reactivity because of the two electronically different metal sites presented. This latest installation from the Thomas group uncovers trends in metal-metal bond distance determined using X-ray crystallography, and uses a variety of spectroscopic (EPR, NMR, Mossbauer) and computational tools to probe the electronic structure of these compounds.  Most interestingly, these compounds are shown to be conformationally flexible, with ligand rearrangements occurring rapidly in solution and this ligand hemilability, which is ideal for facilitating reactivity, can be correlated directly with the strength of metal-metal interactions.

This paper was highly collaborative and its preparation involved researchers from both Brandeis and Harvard University. The synthesis and characterization of the new compounds were largely carried out by Bing Wu, a graduate student in the Thomas group, along with Chris Thomas herself. Matt Wilding, a recent Ph.D. graduate student from the Betley laboratory at Harvard University, assisted with the collection and interpretation of Mossbauer data and designed the cover artwork. Recent Ph.D. graduate Mark Bezpalko, of the Thomas/Foxman groups, and Bruce Foxman carried out all of the structural work in the Brandeis X-ray Diffraction Facility, and all of the computational studies were carried out by Bing Wu and Chris Thomas using the Brandeis high performance cluster.

Irving Epstein has been named AAAS Fellow

irving-epstein

In recognition of his contribution to the study of oscillating chemical reactions, Irving Epstein, the Henry F. Fischbach Professor of Chemistry, has been selected as a Fellow in the American Association for the Advancement of Science (AAAS).

Epstein, who in his 45 years at Brandeis has served as Provost and Dean of the Arts and Sciences, said he was honored to receive the award from the AAAS. “I’m delighted and grateful for the recognition,” he said. “It’s always nice to be appreciated by fellow scientists.”

 

Division of Science Hosts the 2016 Undergraduate Science Symposium

Written by Jena Pitman-Leung.

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The Division of Science Graduate Affairs group hosted the 2nd annual Brandeis University Undergraduate Science Symposium on Saturday 17th, 2016. More than 60 students representing institutions from Massachusetts, Rhode Island, and New Hampshire attended the event, which was held in the Shapiro Science Center. The morning session included research talks from faculty in the Life Sciences (Don Katz, Liz Hedstrom) and the Physical Sciences (Matt Headrick, Christine Thomas), followed by panel discussions with faculty in the Life Sciences (Liz Hedstrom, Bruce Goode, and Maria Miara) and Physical Sciences (Gabriella Sciolla, Isaac Krauss, Jordan Pollack) on how to apply to graduate school. The students then came together for a networking lunch with Brandeis students, postdocs, and faculty. Lunch was followed by a well attended poster session, where 38 students had the opportunity to present their independent research. The day ended by awarding prizes for the best posters in five disciplines. The winners were:

Biology: Rahim Hirani, Hampshire College, “The regulatory role of Beta-Arrestin 1 in prostate cancer cell proliferation”
Neuroscience: Paige Miranda, Wellesley College, “Metabolic Processes Driving Hippocampal Long Term Potentiatio”
Biochemistry: Myfanwy Adams, Wellesley College, “Expression of a Cardiac ATP-sensitive Potassium Channel in a Heterologous Cell Line”
Chemistry: Natsuko Yamagata, Brandeis University, “Exploring the Unexplored: Supramolecular Hydrogels of Retro-Inverso Peptides for 3D Cell Culture”
Physics: Jameson O’Reilly, Northeastern University, “A capillary-mimicking optical tissue phantom for diffuse correlation spectroscopy”

The Division of Science is committed to supporting local undergraduate research, and is excited about the possibility of these bright young scientist choosing Brandeis for their graduate study. We look forward to hosting similar events in the future!

Four Brandeis Science Grads Receive 2016 NSF Graduate Fellowships

GRFP_logoA science education at Brandeis University can be a springboard to future science achievements. We would like to congratulate four of our science graduates who have received the prestigious National Science Foundation Graduate Research Fellowships for 2016.

Noam Saper

Noam was an outstanding student graduating summa cum laude with highest honors in Chemistry in 2015. At Brandeis, Noam worked in the labs of Prof. Barry Snider and Prof. Christine Thomas. He co-authored 3 publications with Snider and Thomas.

Noam received multiple awards including the Barry M. Goldwater Scholarship (2014); the Elihu A. Silver Prize (2014); and the Doris Brewer Cohen Endowment Award (2015).

Following graduation and enthralled by the mysteries of the west coast, he decided to attend the University of California, Berkeley. Noam is working on mechanistic studies of Ni-catalyzed diaryl ether hydrogenolysis in Professor John Hartwig’s laboratory.

Alexandra Sun

Another outstanding Chemistry student, Alexandra Sun graduated magna cum laude with highest honors in 2015. Alexandra also worked in Christine Thomas’ lab where she carried out research on Transition Metal Complexes Featuring a Redox-Active Bidentate Amido-Phosphido Ligand. Alexandra received the Melvin M. Snider Prize in Chemistry in 2015.

She is currently a first-year student in the Chemistry Department at the University of Michigan working with Professor Corey Stephenson on developing new methods in photoredox catalysis.

Abigail Zadina

Abigail received her BS/MS in Neuroscience in 2013. Working in Michael Rosbash’s lab, she was a co-author on 2 publications and received numerous awards including the Doris Brewer Cohen award and the Elihu Silver Prize. In 2013, Abigail discussed her science experience in the Brandeis publication Imprint.

Following graduation, Abigail worked at Columbia in Richard Axel’s lab. She is currently a PhD student in Neurobiology and Behavior at Columbia University.

Joseph Jacobowitz

Joseph Jacobowitz received his BS/MS in 2014, graduating summa cum laude with Highest Honors in Biochemistry. While a Brandeis undergraduate, Joseph co-authored a publication with his faculty mentor, Doug Theobald. In 2013, Joseph received the Division of Science Prize for Outstanding Research Accomplishment and the William P. Jencks  Award in Biochemistry in 2014.

Joseph is in the Biology PhD program at MIT, working for Jing-Ke Weng on the origins of chemodiversity in plants.

Summer Research at Brandeis

All four science graduates had the opportunity to jump start their careers by doing summer research at Brandeis. Noam, Alexandra and Joseph were Division of Science Summer Undergraduate Research Fellows (SURF). Abigail received a Computational Neuroscience Traineeship.

These undergraduate research programs enable students to spend their summers at Brandeis engaged in intensive undergraduate training and summer research. Both programs provide a stipend, faculty mentoring and full-time lab research. The Summer Undergraduate Research Fellows work culminates in a poster presentation summarizing their work. The SURF program is funded by generous donations from alumni. The Computational Neuroscience Traineeship program begins in the summer and runs through the following academic year. It is funded through a grant from the National Institute on Drug Abuse. 

SPROUT Continues Growing Support for Brandeisian Innovators

Lil_Sprout_smallProgram Will Bestow Up to $100,000 to Promising Research Proposals

Could your research impact the world or do you have an idea that could create positive change? Need funding? SPROUT can help with that.

The popular SPROUT program, now in its sixth year, has announced increased funding for the 2016 round of proposals. SPROUT is funded by the Office of the Provost and run by Office of Technology Licensing. This year the Hassenfeld Family Innovation Center, recently created to support entrepreneurial and innovative collaborations happening across campus, contributed an additional $50,000 to be disbursed among the most promising requests.

Historically, the program has supported a diverse scope of lab-based innovations from all departments in the sciences  including Biology, Biochemistry, Physics, and Chemistry.  Past candidates have proposed projects ranging  from early‐stage research and development to patent‐ready projects ranging from treatments for diseases to lab tools.  Brandeis lab scientists have pitched their projects, including HIV vaccines (Sebastian Temme, Krauss lab),  neuroslicers (Yasmin Escobedo Lozoya, Nelson lab) and the use of carrot fiber as an anti-diabetic  (Michelle Landstrom, Hayes lab) to a panel of distinguished, outside judges. A SPROUT award can jumpstart your innovation and lead to continued opportunities. SPROUT awardees researching the use of carrot fiber as an anti-diabetic food agent were just awarded additional funding by the Massachusetts Innovation Commercialization Seed Fund program.

Other successful projects include “Enzymatic Reaction Recruits Chiral Nanoparticles to Inhibit Cancer Cells” led by Xuewen Du from the Xu lab, “Semaphorin4D: a disease‐modifying therapy for epilepsy” led by Daniel Acker of the Paradis lab, “X‐ray transparent Microfluidics for Protein Crystallization” led by Achini  Opathalage from the Fraden lab and “New and Rational Catalyst Development for Green Chemistry”  from the Thomas lab.  Those interested in learning more about past SPROUT winners are invited to read this recent Brandeis NOW article. A list of additional winners, along with their executive summaries, is available on the Brandeis OTL website.

Teams seeking support for scientific projects which require bench research, lab space, and/or lab equipment are encouraged to submit an abstract prior to the March 7 deadline. The competition is open to the entire Brandeis community including faculty, staff, and students. The Office of Technology Licensing will conduct information sessions on Thursday, February 25th 11:30 a.m.‐12:30 p.m. in Volen 201 and on Monday, February 29th 1:00 p.m.‐2:00 p.m. at the Shapiro Science Center, 1st Floor Library. Staff will address the application process as well as specific questions and interested applicants are highly encouraged to attend.

More details regarding the SPROUT awards, process and online application may be found at bit.ly/SPROUT16.

Why Fire Is Hot

A recent paper by K. Schmidt-Rohr (Chemistry) answered the question why combustion reactions are always exothermic.  Every scientist should be able to explain what makes fire hot, but neither chemistry nor combustion textbooks have provided a valid answer. Schmidt-Rohr’s analysis shows that the reason lies in the double bond in O2, which is much weaker than other double bonds or pairs of single bonds in the biosphere, so that the formation of the stronger bonds in CO2 and H2O results in the release of heat. The bond energies in the fuel play only a minor role; e.g., the total bond energy of CH4 is nearly the same as that of CO2. A systematic analysis of bond energies gives the heat of combustion close to –418 kJ (i.e., –100 kcal) per mol O2, in good agreement (±3%) with data for >500 organic compounds; the heat of condensation of H2O (–44 kJ per mol H2O(l)) is also included in the analysis. For 268 molecules with ≥8 carbon atoms, the standard deviation is even smaller, 2.1%. For a fuel of composition CcHhOoNn, this gives DcH ≈ -418 kJ (c + 0.3 h – 0.5 o), which enables instant estimates of heats of combustion simply from the elemental composition, even for complex mixtures of unknown molecular composition, and explains principles of biofuels production. The analysis indicates that O2, rather than fuels like octane, H2, ethanol, or glucose, is the crucial “energy-rich” molecule. It also challenges common notions about a relation between the oxidation state and the energy content of biomolecules.

BlogCombustExotherm.0116

One then needs to explain why O2 is abundant in air despite its high enthalpy: All the O2 in the earth’s atmosphere has been produced by photosynthesis in cyanobacteria, algae, and higher plants, as a by-product of photosynthetic proton and electron production from H2O. The “price” of the production of O2, which is energetically so unfavorable, is paid by plants and algae (with “cheap” energy from the sun) in order to be able to live wherever H2O is present. So one can conclude that atmospheric O2 stores solar energy that sustains us with every breath we take.

Schmidt-Rohr K. Why Combustions Are Always Exothermic, Yielding About 418 kJ per Mole of O-2. J Chem Educ. 2015;92(12):2094-9.

Casey Wade Receives Grant from ACS Petroleum Research Fund

prf_figure_CWadeAssistant Professor of Chemistry Casey Wade has been selected to receive a Doctoral New Investigator grant from the American Chemical Society Petroleum Research Fund for his proposal, “Metal-organic Framework Supported Pincer Complexes: Investigation of the Effects of Site Isolation and Secondary Environment.” The two year grant will support the development of improved heterogeneous catalysts for the production of petroleum-derived commodity and fine chemicals.   Wade and coworkers plan to incorporate reactive transition metal catalyst sites into the well-defined 3-dimensional porous structure of metal-organic frameworks (MOFs). While the porous MOF support can be used to tune and promote reactivity, the immobilization of catalytically active sites prevents undesired bimolecular decomposition pathways and facilitates catalyst separation, leading to greener and more sustainable catalytic processes.

Post written by Christine Thomas

Putting “umpolung” to work in synthesis of nitrogen-bearing stereocenters

Professor Li Deng‘s lab in the Brandeis Chemistry Department has recently published a high-profile paper in Nature, disclosing an important advance in the chemical synthesis of organic molecules containing nitrogen. Li Deng writeup 1

A great number of important drugs contain at least one nitrogen atom connected to a “stereogenic” carbon atom. Stereogenic carbons are connected to four different groups, making possible two different configurations called “R-” or “S-”. In synthesizing a drug, it can be disastrous if the product does not have the correct R/S configuration.  For instance, the morning-sickness drug Thalidomide caused birth defects in ~10,000 children because it was a mixture of R and S molecules.Li Deng writeup 2

Selective preparation of only R or only S molecules containing nitrogen is a major challenge in organic chemistry. Many recent approaches have formed such stereocenters by use of an electron rich “nucleophile” to attack an electron poor “imine”. Deng is now the first to report an unconventional strategy in which the polarity of the reaction partners is reversed. In the presence of base and a creatively designed catalyst, the imine is converted into an electron rich nucleophile, and can attack a variety of electrophiles. Deng’s catalysts are effective in minute quantities (as low as 0.01 % of the reaction mixture), and yield products with R- or S- purities of 95-98 %.

In addition to Professor Deng, authors on the paper included former graduate student Yongwei Wu PhD ’14, current Chemistry PhD student Zhe Li, and Chemistry postdoctoral associate Lin Hu.

Wu Y, Hu L, Li Z, Deng L. Catalytic asymmetric umpolung reactions of imines. Nature. 2015;523(7561):445-50. (commentary)

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