Christopher Hossack, Graduate Student, Cahill Lab, GW Department of Chemistry

The Department of Chemistry Presents:  Christopher Hossack, Graduate Student, Cahill Lab, GW Department of Chemistry

Lanthanide (Ln) pyrazolylborates are a diverse class of molecular materials that have found applications as catalysts, light-emitting devices and single molecule magnets, owing to properties such as sensitized Ln 3+ emission and slow magnetic relaxation. An understudied aspect of this class of materials are lanthanide pyrazolylborates functionalized with strongly electronwithdrawing groups, the introduction of which presents the opportunity to tune the chemical environments and subsequent properties of the resultant complexes via judicious choice of ring substituent. For example, a nitro- (NO 2 ) group could have a structure-directing effect on the coordination of lanthanide ions, as a fourth binding site is available in the form of the oxygen atoms. Moreover, the strongly electron-withdrawing nature of the nitro- group has the potential to influence the π* orbitals of the pyrazole rings, affecting the crystal field experienced by the Ln 3+ ion, and in turn the photophysical and magnetic properties of resultant complexes. Herein, we present the syntheses, crystal structures, photophysical and magnetic properties of a family of lanthanide pyrazolylborate complexes utilizing a mono-n- nitrotrispyrazolylborate, n-NO 2 Tp – (n = 3, 4) ligand. The reported complexes feature molecular structural diversity and tunable nuclearity, Ln 3+ sensitization and dual visible and near-IR emission, charge transfer optical transitions as well as slow magnetic relaxation. The variable chemical environments afforded by the reported compounds allow us to study how substituent effects influence both the optical and magnetic properties of f-block materials and may yield valuable insights in the fundamental behavior of f-electrons.

BIO

Christopher received his B.S. in Special Chemistry from the University of the West Indies, Mona in Kingston, Jamaica in 2019. He was an undergraduate researcher under Dr. Marvadeen Singh-Wilmot on the synthesis of novel lanthanide metal-organic frameworks, primarily for luminescence sensing applications. Christopher then joined the Chemistry Department at The George Washington University under both Professors Claire Besson and Christopher Cahill. He is currently studying the photophysical and magnetic properties functionalized lanthanide trispyrazolylborate complexes.