Nickel hydride catalyst

Neutrons Uncover Clues for Better Catalysts

CINS Scattering Spotlight: Dr. Manar Shoshani

Source: Mitchell DiPasquale 
Contact: webmaster@cins.ca
Image: A) 1.5 mm3 single crystalline nickel-hydride for neutron diffraction. B) Neutron diffraction-solved structure. C) ChemDraw depiction of cluster.

From cleaning the toxic exhausts of your car’s engine, to the green promise of plastic upcycling, to the biological processes that keep you alive – achieving efficient results in chemical changes is driven by catalysts.

The ability of nature to selectively carry out multi-electron chemistry under ambient conditions has long inspired catalytic design.  Innovation in synthetic catalysts can unlock novel reactions and allow cheaper, cleaner, and more efficient pathways to new and improved materials.

Dr. Manar Shoshani
Dr. Manar Shoshani

Former UWindsor PhD student Manar Shoshani took inspiration from multi-metallic enzyme active sites to try to emulate this robust reactivity in homogenous transition metal clusters. Under the guidance of Dr. Samuel A. Johnson, Manar sought to understand how the multi-metal centres interact to promote catalysis, with hopes of providing a trajectory toward intelligent design of better catalysts. 

With molecular nickel-hydride clusters, Manar observed remarkable activations of C–C, C–O, and C–S bonds as well as catalytic activation of C–H bonds, all of which proceeded rapidly at room temperature. Knowledge on the solid-state structure of the complex is vital to decipher the mechanistic intricacies that drive these processes.

“Determining the unambiguous solid-state structure of these complexes is imperative to understanding both the properties of the cluster, as well as the potential for these clusters to serve as catalysts.”

– Dr. Manar Shoshani, Caltech Post-Doctoral Fellow

Synthetic chemists naturally lean on X-ray crystallography for structural information; however, light atoms (particularly hydrogen), coordinated in these complexes are largely invisible to studies by X-ray. For Manar, neutron diffraction served as the ideal complement to be able to pinpoint the hydride locations in the cluster, and to clue into the details of metal-metal cooperativity.

A step further, as neutrons interact with hydrogen and deuterium differently, the experiment also provided insight into the catalytic hydrogen-deuterium exchange activity of the clusters. Neutrons offer an exceptional means to uncover the finesse of transition metal hydride catalysts. A deeper understanding of metal-metal cooperativity can help usher in a new wave of efficiency with rationally designed catalysts.

After completing his PhD, Dr. Shoshani continues to contribute to catalyst innovation as a post-doctoral fellow at the California Institute of Technology.

For more information on this work, the published manuscript can be found at Shoshani, Manar M., Robert Beck, Xiaoping Wang, Matthew J. McLaughlin, and Samuel A. Johnson. Inorganic Chemistry 57, 5 (2017): 2438-2446.

CINS Scattering Spotlight aims to raise awareness for the world-class neutron research being conducted by students across Canada. We encourage you to share your research stories by contacting tharroun@brocku.ca

Atomic structure of a mineral perovskite

Neutrons Point to Next-Generation Computer Memory Materials

CINS Scattering Spotlight: Dr Dalini Maharaj, TRIUMF

Source: Mitchell DiPasquale 
Contact: webmaster@cins.ca
Image: Crystal structure of a mineral perovskite. (Wikimedia CC-BY-SA 3.0)

As our music and movie libraries grow and the number of apps we use multiplies, everyone wants faster devices with larger data storage. Former McMaster PhD student Dalini Maharaj studies novel magnetic materials that could very well usher in the next generation data storage technology, particularly in disk drive read-and-write heads. In principle, one could reduce the size of the data storage unit if the data density could be increased in these hard-disks. New kinds of quantum materials are needed to fulfil this promise.

“Of course, before these new technologies can be realized, much work needs to be performed to understand the properties of the candidate materials.” – Dr. Dalini Maharaj, TRIUMF Post-Doctoral Fellow

Dr. Maharaj’s PhD work involved the study of the quantum magnetic properties of crystalline materials via X-ray and neutron scattering methods. Working in Prof. Bruce D. Gaulin’s group at McMaster University, she synthesized novel materials which are theoretically predicted to exhibit exotic magnetic properties. This class of materials, referred to as the double perovskites, have phases that involve `frustrated` magnetic interactions, whereby the magnetic dipoles of the atoms cannot arrange themselves into a low energy configurations. Members of this family are widely studied as they are shown to exhibit a wide variety of unique properties including superconductivity, ferroelectricity and colossal magnetoresistance, the latter being a prime candidate for increasing the data density of hard drives. In particular, Dalini’s doctoral work involved the study of non-trivial arrangements of magnetic atoms in d-electron double perovskites which are driven by magnetic interactions that can only be theoretically analysed with advanced quantum mechanics.

Dr. Dalini Maharaj

Neutrons are an indispensable probe of the magnetic properties of materials as they are electrically neutral and they possess the property of spin. These properties enable neutrons to deeply penetrate matter and interact directly with the magnetic degrees of freedom in solid state materials. The energy spectra which are obtained from neutron scattering experiments provide important clues for identifying the magnetic ground state of the materials being investigated.

Most recently, Dalini’s neutron scattering studies on the cubic double perovskite materials led to discover the first instance of octupolar order in d-electron magnets. This discovery highlights the relevance of multipolar interactions in heavy d-electron magnets and consequently, the potential for the realization of novel materials for future applications.

Upon completing her PhD, Dalini remained in the field of neutron sciences and is currently completing a postdoctoral fellowship at TRIUMF, through the University of Windsor, studying potential targets and moderators for a future compact accelerator neutron source.

CINS Scattering Spotlight aims to raise awareness for the world-class neutron research being conducted by students across Canada. We encourage you to share your research stories by contacting tharroun@brocku.ca

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