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.

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)

IrvFest 2015 – Friday, July 17

The IrvFest 2015 talks will be held in the Shapiro Campus Center tomorrow (Friday, July 17), starting around 8 am and running all day. The IrvFest 2015 schedule is available.

IrvFest 2015 is a celebration of Irv Epstein’s great contribution to science and the science community.

Here is datum from the Epstein group: A GIF of a spiral where the wave move toward the center of the spiral ( antispirals). If you find it hypnotizing, you might also find the talks tomorrow beautiful and interesting.

Here’s another cool GIF. For a more detailed explanation of the experiment see: hopf.chem.brandeis.edu.

There will be survey of work in the field presented by well respected members of the community, as well as some work that is semi- far afield where students and collaborators of Irv have settled down. Some of these talks will be more on the theoretical side and some will be experimental. Irv’s legacy is diverse!

Isaac Krauss Wins 15th Annual Strage Award

Dr. Isaac Krauss, Assistant Professor of Chemistry, will be awarded the 15th Annual Alberta Gotthardt and Henry Strage Award for Aspiring Young Science Faculty on Wednesday, April 15 in Gerstenzang 123 at 2:00 PM.

In his annIsaac Kraussouncement, John F. Wardle, Chair of the Strage Award Selection Committee, said “Isaac has been recognized as one of the up and coming scientists in the field of chemical glycobiology. His work on carbohydrate recognition and direct evolution has been highlighted in Chemical & Engineering News and Faculty of 1000 Prime, and reviewed in Nature Chemical Biology and Current Opinion in Chemical Biology.

Dr. Krauss has also received the 2013 National Science Foundation CAREER Award and the 2012 Thieme Chemistry Journal Award.

Learn more about Dr. Krauss’ research

SPROUT grant opportunity for 2015 announced

From the Brandeis Office of Technology Licensing:

The Brandeis Virtual Incubator invites members of the Brandeis Community (faculty, staff and students) to submit an application for the SPROUT Program. These Awards are intended to stimulate entrepreneurship on campus and help researchers launch their ideas and inventions from the lab to the marketplace.The SPROUT Program will provide pilot funding for innovative scientific projects within the Division of Science that require bench research, lab space, and/or lab equipment.

We will be awarding $50,000 to be shared among the most promising proposals.
Come get your questions answered at one of our upcoming information sessions.
Info Sessions: 
Thursday, February 26,  11:00 a.m.-12:00 p.m. (Volen, room 201)
Monday, March 2,  2:00 p.m.-3:00 p.m.   (Shapiro Science Center, 1st Floor Library, room 1-03)
 
Deadlines: Preliminary Proposals are due by Friday, March 6th
Please note, the introduction of the new SPARK Program geared towards innovative non-bench projects that have impact. An additional email will be sent detailing this program.
For more information on each program go to our website or contact the OTL program leaders,  Melissa Blackman for SPROUT and  Anu Ahuja  for SPARK.

MRSEC Summer Undergraduate Research Fellowships (2015)

The Division of Science wishes to announce that, in 2015, we will offer  MRSEC Summer Undergraduate Research Fellowships for Brandeis students doing undergraduate research, sponsored by the Brandeis Materials Research Science and Engineering Center.The due date for applications  is February 24, 2015,  at 6:00 PM EST.MRSEC Summer Undergraduate Research Fellowships will provide $5000 in stipend support to allow students to do summer research in MRSEC labs (housing support is not included). Students who will be rising Brandeis sophomores, juniors, or seniors in Summer 2015 (classes of ’16, ’17, and ’18). No prior lab experience is required. A commitment from a Brandeis MRSEC member to serve as your mentor in Summer 2015 is required.The Division of Science Summer Program will run from May 26 – July 31, 2015. Recipients are expected to be available to do full time laboratory research during that period, and must commit to presenting a poster at the final poster session on July 30, 2015. Five positions are available.The application form is online (Brandeis login required). Questions that are not answered in the online FAQ may be addressed to Steven Karel <divsci at brandeis.edu>
 
 

Irving Epstein Interviewed by NPR about Alan Turing

Alan_Turing_photob_0Irving Epstein, Professor of Chemistry, was recently interviewed by NPR about Alan Turing and a paper (Testing Turing’s theory of morphogenesis in chemical cells) that he co-authored with Nathan Tompkins, Ning Li, Camille Girabawe, Michael Heymann, Seth Fraden and G. Bard Ermentrout earlier this year. The paper discussed an experiment that they performed that confirmed and improved upon Alan Turing’s theory about morphogenesis.

Alan Turing is credited with inventing the modern computer and breaking the German Enigma code during World War II. That work is spotlighted in the upcoming movie titled “The Imitation Game”. After World War II, Turing turned his focus to biology. He investigated how a single embryonic cell develops into a complex organism with hundreds of different kinds of cells. He wrote The Chemical Basis of Morphogenesis in 1952.

Listen to the interview …

Protected by Akismet
Blog with WordPress

Welcome Guest | Login (Brandeis Members Only)