Dissertation/Thesis Abstract

Synthesis, Reactivity and Spectroelectrochemistry of Ruthenium Schiff Base Methoxide Complexes
by Shrestha, Kailash, M.S., Southern Illinois University at Edwardsville, 2020, 97; 27957562
Abstract (Summary)

In the pursuit of understanding the chemistry of the {HNO} species in biological systems, different synthetic approaches were applied to move forward to synthesize model complexes in the Shaw lab. First, new salchy and saloph family ruthenium alkoxide and methylimidazole complexes were synthesized. Crystals were isolated and characterized through 1H NMR spectroscopy, FTIR spectroscopy, and X-ray powder diffraction. The redox chemistry of these complexes, except the salchy 1-methylimidazole complex, were also analyzed through electrochemistry as well as IR-spectroelectrochemistry under inert conditions.

Looking at the reduction of alkoxide complexes, Ru(NO)(tBu4saloph)(OCH3) shows an irreversible wave due to breakdown of the methoxide ligand while Ru(NO)(tBu4salchy)(OCH3) is difficult to reduce within the DCM potential window. Two well behaved reversible oxidation waves, one electron transfer on each oxidation, were observed in both complexes. The reduction irreversibility of the salchy methoxide was analyzed in acetonitrile, which can also participate as an electrochemically detectable ligand in the complex. Although the reduction wave showed poor reversibility, a sign of a good reversible wave for the acetonitrile complex (presumably) was also observed. Concurrently, the same complex solution was also used to study the concentration-dependent study. There was no evidence of any improvement in the reversibility of the complex nor any effect of the addition of the complex in the solution.

The isolation of methylimidazole complexes and their reduction showed promising features to achieve {Ru(HNO)} species. Electrochemistry of the ruthenium saloph methylimidazole cationic species gives two good reduction reversible waves with {RuNO}6/7 and {RuNO}7/8 redox couples. Also, the change of reduction peak by more than 300 wavenumbers in the difference IR spectrum indicates that the core metal center participates in the reduction process rather than the ligand itself. It opens the possibility of a hydride reaction with {Ru(NO)}6 species or proton reactivity with {Ru(NO)}8 species to achieve {Ru(HNO)} and is a probe into its electrochemical behavior.

Finally, a 1H NMR test tube reaction was performed with alkoxide complexes of both the saloph and salchy families. Distinction peak movements were observed through stepwise protonation at the methoxide ligand and its detachment from the complexes. This vacant coordination site can be exploited with a suitable ligand and to investigate its redox chemistry.

Indexing (document details)
Advisor: Shaw, Michael J.
Commitee: Voss, Eric J., Jones, Myron W.
School: Southern Illinois University at Edwardsville
Department: Chemistry
School Location: United States -- Illinois
Source: MAI 81/12(E), Masters Abstracts International
Subjects: Chemistry, Inorganic chemistry
Keywords: Methoxide complexes, Ruthenium Shiff base, Electrochemistry
Publication Number: 27957562
ISBN: 9798645498979
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