Thursday, October 12
11:30 a.m.
Engineering Computer Science Building, Room 116
and Zoom https://uvic.zoom.us/j/83657240884?pwd=3pDZp5892dS4gsAKoaplX1t2j9kgbh.1
Thursday, October 5
11:30 a.m.
Engineering Computer Science Building, Room 116
and Zoom https://uvic.zoom.us/j/83657240884?pwd=3pDZp5892dS4gsAKoaplX1t2j9kgbh.1
Monday, September 25
11:30 a.m.
Engineering Computer Science Building, Room 116
and Zoom https://uvic.zoom.us/j/83657240884?pwd=3pDZp5892dS4gsAKoaplX1t2j9kgbh.1
Abstract: Pd-catalyzed cross-coupling reactions are among the most powerful transformations in organic synthesis. Nevertheless, controlling selectivity can be problematic when employing substrates with more than one (pseudo)halide. Two such challenges are discussed in this presentation. Overfunctionalization is one challenge: it can be difficult to control even with carefully tuned stoichiometry. We have investigated the mechanistic origin of ligand effects on controlling between mono- versus diarylation in Suzuki cross-couplings. Ligand sterics influence the competition between two pathways: a bimolecular mechanism for dissociation of the mono-coupled product from Pd versus a second oxidative addition event. Our studies provide insight into strategies to minimize (or maximize) polyfunctionalization in cross-coupling reactions. This presentation will also describe another selectivity challenge that arises with dihalogenated heteroarenes. Most dihaloheteroanes undergo cross-coupling reactions with a strong preference for breaking one C–halide bond over the other. For a few such substrates, catalyst-controlled approaches have been described that enable inversion of the conventional site selectivity. However, 2,4-dihalopyrimidines are particularly resistant to change: they always undergo cross-coupling at C4, and SNAr reactions also tend to favor that site. We recently developed a method to preferentially cross-couple at the C2 position of 2,4-dihalopyrimidines. The selectivity is surprising, and preliminary mechanistic investigation suggests that C—X cleavage does not take place through a traditional oxidative addition mechanism.
Visit https://events.uvic.ca/chemistry/ for the full list of 2023-2024 Chemistry seminars.
The Chemistry Seminar Program brings visitors from across Canada and beyond to present seminars in their area of expertise. The seminars are open to everyone, including undergrad students.
Monday February 6
11:30 am
ECS 116 and Zoom
Computational modelling of chemical reactions at surfaces
Irina Paci
UVic – Chemistry Department
https://uvic.zoom.us/j/83657240884?pwd=3pDZp5892dS4gsAKoaplX1t2j9kgbh.1
Meeting ID: 836 5724 0884
Password: 379943
The Chemistry Seminar Program brings visitors from across Canada and beyond to present seminars in their area of expertise. The seminars are open to everyone, including undergrad students.
Monday January 30
11:30 am
ZOOM
https://uvic.zoom.us/j/83657240884?pwd=3pDZp5892dS4gsAKoaplX1t2j9kgbh.1
Meeting ID: 836 5724 0884
Password: 379943
Cameron Jones
Monash University
Magnesium (I) Compounds: Humble Reagents with Noble Intentions in Synthesis and Small Molecule Activations
Since the synthesis of the first stable magnesium(I) compounds was achieved in 2007, the unique properties that these species possess has lent them to use as versatile reducing agents in both organic and inorganic synthetic protocols.[1] The products of such reactions are often inaccessible using more classical reducing agents. We have recently developed several classes of highly activated magnesium(I) and “masked” magnesium(I or 0) systems, and have shown these to be markedly more reactive than their established counterparts. In this lecture it will be shown that these, and related heavier alkaline earth, compounds are powerful reagents for the “transition metal-like” activation of catalytically relevant small molecules and inert arenes (e.g. CO, H2, C2H4, N2, C6H6) (Figure 1).[2-6] In several cases, small molecule activations are redox reversible under mild conditions, which gives hope for the eventual incorporation of cheap, non-toxic magnesium(I) (and heavier group 2 metal) compounds into catalytic cycles, normally requiring expensive and toxic late transition metal complexes to proceed.
The Chemistry Seminar Program brings visitors from across Canada and beyond to present seminars in their area of expertise. The seminars are open to everyone, including undergrad students.
Monday January 16
11:30 am
Engineering and Computer Science Bldg, Room 116
Morris Bullock
Pacific Northwest National Laboratory
Stalking and Capturing Elusive Monomeric Copper Hydrides
Copper hydrides were first reported in 1844; their value as catalysts for organic reactions has significantly expanded in the last two decades. Copper hydrides with NHC (NHC = N-heterocyclic carbene) ligands typically exist as dimers, [(NHC)Cu(m-H)]2. The kinetics of insertion of organic substrates into the Cu-H bond are determined by the electronic properties of the substrates. Conversion of the dimer to a monomeric species or insertion into the Cu-H bond can be rate-determining. Remote ligand modification can have a large effect on the dimer-monomer equilibrium, even when substituents are several bonds away from the copper. Destabilization of the [(NHC)Cu(m-H)]2 dimer relative to the (NHC)Cu-H monomer enables the isolation of rarely observed Cu-H monomers. These highly reactive monomeric complexes insert tri-substituted alkenes into the Cu-H bond.
The Chemistry Seminar Program brings visitors from across Canada and beyond to present seminars in their area of expertise. The seminars are open to everyone, including undergrad students.
Monday January 9
11:30 am
Engineering Computer Science Bldg, Room 116
Tehshik Yoon
University of Wisconsin-Madison
“Base Metals in Photoredox Oxidation Reactions”
Photocatalysis offers a uniquely facile strategy for the generation of a wide variety of open-shell intermediates, and the development of new photoredox transformations based upon their reactivity has been a major theme of research in the past decade. This broad effort has led to the development of a remarkable variety of net redox-neutral and, to a lesser extent, net-reductive transformations of significant synthetic utility. The development of net-oxidative photoredox transformations, in contrast, has been somewhat slower, due to the incompatibility of photoredox conditions with many of the terminal oxidants that are ideally suited to ground-state oxidative catalysis. We propose that simple base metal salts are inexpensive, earth-abundant, and environmentally benign terminal oxidants that readily support the one-electron oxidation state changes typical of photoredox reactions. Their incorporation into the design of photoredox reactions enable a broad range of useful net oxidative photochemical transformations.
The Chemistry Seminar Program brings visitors from across Canada and beyond to present seminars in their area of expertise. The seminars are open to everyone, including undergrad students.
Monday October 17
11:30 am
David Turpin Building A110
Juewen Liu
University of Waterloo
http://www.science.uwaterloo.ca/~liujw/index.html
“DNA adsorption on gold nanoparticles, graphene oxide and metal oxides”
Understanding and control of DNA adsorption on surfaces and nanoparticles is critical for biosensor development. This seminar covers detailed studies on three types of important nanomaterials. DNA adsorbs on gold nanoparticles via very strong base coordination. Such strong adsorption led to kinetic controlled processes. DNA as an interesting block copolymer with many negative charges has interesting self-assembly properties as a function of ionic strength, pH and temperature, all of which have been used to promote DNA adsorption to gold. Such understanding has led to not only better conjugation methods but also better biosensors. DNA adsorbed on graphene oxide via hydrogen bonding along with pi-pi stacking, while they adsorb to metal oxides via phosphate backbone binding along with some base interactions. Some literature reported sensors are reviewed and some sensing mechanisms were found to be incorrect due to a lack of attention to fundamental DNA adsorption mechanisms.
The Chemistry Seminar Program brings visitors from across Canada and beyond to present seminars in their area of expertise. The seminars are open to everyone, including undergrad students.
Thursday October 13
11:30 am
David Turpin Building A110
Oleksandr Voznyy
University of Toronto, Scarborough
http://www.mapageweb.umontreal.ca/waldronk/Files/Home.html
“Applications of machine learning for studying phase stability in energy materials”
There is a growing demand for design and discovery of new materials that can replace their costly counterparts without the loss of performance. Focusing on clean energy applications, our experimental efforts show that in catalysis, batteries and photovoltaics, even minor changes to the material composition (using alloying or doping) may bring substantial benefits to materials’ performance. However, it is becoming increasingly evident that traditional trial and error methods are simply too inefficient, given the vastness of the chemical combinatorial space, where human intuition is often inadequate to capture the trends in materials properties. We find that having one tool that could predict formation energies and bandgaps for arbitrary materials, provided the accuracy is adequate, could help address a host of problems in a vast range of clean energy applications. In this talk I will present our efforts in developing such a tool and the advances we’ve made in improving the accuracy of such predictions (in particular, formation energies). I will also demonstrate how this simple tool can be used for predicting battery cathode voltages, solid electrolytes ionic conductivity, solar cells phase stability, and catalysts’ stability in acid.
