Use of Oximes and Schiff-bases as Bridging/Chelating Ligands with Select 3d and 3d/4f Ions in Cluster Chemistry and a Mechanistic Insight into the Roles of Transition Metal Ions in the Formation of Tetrazoles

The employment of acenaphthenequinone dioxime (acndH2), 9,10-phenanthrenedione-9-oxime (phenoxH), 9,10-phenanthrenedione-9,10-dioxime (phendoxH2), and N-naphthalidine-2-amino-naphthol (nanpH2) in homometallic 3d- and heterometallic 3d/4f-metal cluster chemistry has afforded a Mn cluster and novel families of Mn/Ln and Cu/Ln complexes. In Chapter 2, the synthesis and characterization of the {MnIIIMnIV2} (1), {GdMnIV2} (2) and {DyMnIV2} (3) compounds resulting from the use of the acndH2 ligand is reported. It is the first reporting of the acndH2 ligand in heterometallic Mn/Ln cluster chemistry. Complexes 1−3 allowed for a magneto-structural correlation as the topology, nuclearity, and metal oxidation state descriptions remained the same among this family of clusters. Magnetic studies show that 2 exhibits a larger-spin relative to 1, and 3 demonstrates SMM behaviour. In Chapter 3, the mono- and dioxime ligands, phenoxH and phendoxH2, which are structurally similar to the acndH2 ligand, were synthesized and employed in Cu/Ln chemistry. The deprotonated phenoxH ligand provides a new family of {Cu3Ln} (Ln = Gd (4), Tb (5), Dy (6)) complexes, affording the first reported oximato-bridged {Cu3Ln} clusters. The structural and magnetic characterization of compounds 4−6 reveal a “propeller”-like core and SMM behaviour for 5 and 6. Chapter 4 presents the use of nanpH2 in heterometallic 3d/4f-metal cluster chemistry for the first time. A new family of {MnIII12LnIII6} clusters (Ln = Y (7), Gd (8), Dy (9)) containing the nanpH2 ligand were isolated. Complexes 7−9 are high-nuclearity complexes and of high-symmetry. They exhibit inorganic cores where the LnIII ions are all 8-coordinate, making them the first reported {MnIII12LnIII6} clusters with such a topology. These complexes display dominant ferromagnetic exchange interactions, and SMM behaviour was observed for 9. In Chapter 5, the metal-catalyzed azide-acetonitrile cycloaddition process for the NiII, CuII and ZnII transition metal ions affording 5-methyl-tetrazolate (mtz-) heterocycles were computationally investigated via density functional theory (DFT). This is the first computational study to investigate the role of NiII in this cycloaddition reaction. Although a higher- and lower-level of theory was utilized during the DFT studies, both calculations reveal that the lowest energy pathway always occurs via a nitrile coordinated transition state that is either 5- or 6-coordinate, corresponding to the CuII-, and ZnII/NiII-catalyzed cycloaddition, respectively. The calculations show that ZnII and CuII afford the lowest energy transition states, according to the lower and higher levels of theory, respectively. The preferred coordination numbers of the metal ions, along with the preferred N donor atoms of the mtz− anion, were calculated and compared with the experimental observations drawn from the Cambridge Structural Database (CSD). The most stable structures for NiII and CuII are N2 bound and possess octahedral geometry, while N1 coordination and trigonal bipyramidal geometry is preferred for ZnII. Lastly, the isomerization process was investigated for the 6-coordinate cyclized NiII product, showing that the system is expected to isomerize to the thermodynamically favoured product after the initial cyclization.

Name thesis:degree_name

Ph.D. Chemistry

Level thesis:degree_level

Doctoral

Discipline thesis:degree_discipline

Faculty of Mathematics and Science

Department dc:contributor.department

Department of Chemistry

Grantor

Brock University

Year dc:date.issued

2025

Author dc:creator

• Worrell, Anne

• Oximes
• Schiff-Bases
• Single-Molecule Magnets
• Coordination Chemistry
• Density Functional Theory

Language dc:language.iso

eng

Handle dc:identifier.uri

https://hdl.handle.net/10464/19130

OAI identifier oai:identifier

oai:brocku.scholaris.ca:10464/19130