Tuning chemical properties of heterobimetallic complexes and transition metal dichalcogenides

Abstract

A comprehensive understanding of the chemical and structural properties of the inorganic materials that are promising candidates for use in catalysis and optoelectronic devices is necessary for their development in practical applications. This knowledge is crucial in guiding rational design to enhance the properties of materials for desired applications. Our laboratory focuses on two different types of materials, intermetallics and semiconductors, which have attracted interest in the aforementioned applications. Heterobimetallic complexes, containing a bond between two different metals (M and E) display excellent catalytic properties and are useful as single-source precursors for the synthesis of intermetallic nanomaterials. The reactivity of heterobimetallic complexes can be modified by altering the metal-metal (M-E) bonding through changes to the surrounding ligands. However, much needs to be learned about the effects of different ligands on the use of such complexes for catalysis and the synthesis of intermetallic materials. Transition metal dichalcogenides (TMDCs) have emerged as a novel class of two-dimensional semiconductors due to their layered structures and tunable dimensionality resulting in their potential utility in optoelectronic devices. Nevertheless, our understanding of the impacts of ball-milling or annealing methods, which are used to manipulate the structure and dimensionality of TMDCs remains to be studied. Moreover, revealing the chemical transformation of heterostructured or alloyed TMDCs with routine characterization techniques is challenging. This dissertation is comprised of three sections. First, we investigate the binding affinity of phosphine ligands to heterobimetallic group 10-14 complexes both computationally and experimentally. We further examine the catalytic effect of the heterobimetallic complexes with different phosphine ligands in Negishi coupling reactions between ethyl-2-iodobenzoate and cyclohexyl zinc chloride. The catalysis experiments reveal relationships between the specific phosphine ligand used and the catalytic activity of the complexes. Second, shifting the focus from heterobimetallic complexes to TMDCs, we observe chemical-induced slippage, which is triggered by grinding the bulk WSe2 with dimethyl sulfoxide. Close examination of WSe2 with Raman spectroscopy provides evidence for slippage that agrees with trends in both experimental and simulated powder X-ray diffraction patterns. Lastly, we study the effect of mixing and alloying of TMDCs using a combination of powder X-ray diffraction and 77Se solid-state nuclear magnetic resonance spectroscopy. We find that various reaction conditions for mixing two binary TMDCs result in different transformations in their morphology and optical properties. Our efforts to tune the chemical properties of materials offer broad insights for understanding their structural and optical properties for future applications in optoelectronics.