| dc.description.abstract | Dirhodium complexes are used for a broad scope of applications due, in part, to the presence of a stable RhII-RhII bond which has a remarkable ability to adapt to a rich variety of ligands for the tuning of electronic and structural properties. The results described in this dissertation encompass three examples of ligand field design for synthesizing new dirhodium complexes with prospects for medicinal and electrocatalytic applications as well as discovering unprecedented structures. Synthetic details of these complexes are presented along with structural, spectroscopic, electrochemical studies along with biological assays for key compounds. Theoretically obtained results are also provided to supplement experimental data.
Reactions of bis(1,5-COD)dirhodium(I) dichloride (COD = 1,5-cyclooctadiene) with 2-mercapto-6-methylpyridinate (mmp) led to the formation of [RhI(mmp)(COD)]2. Its ability to undergo two reversible redox events allowed for the isolation of this compound in oxidation states RhIRhI, RhIRhII, and RhIIRhII, constituting a novel structural motif without the metal-metal σ-bond. The RhIIRhII species exhibits strong antiferromagnetic coupling between the RhII spin centers due to significant overlap between RhII 4dz2 and S3pz orbitals.
A series of complexes of general formula cis-(Rh2[(µ-C6H4)P(Ph)2]2[L]2)[BF4]]2 were prepared in order to explore the effect of diimine ligand “L” on the compounds’ electronic and redox properties. The complexes’ properties were studied by changing the coordinating nature of the diimine ligand (µ2-bridging 1,10-phenanthroline versus κ2-chelating 1,8-diazanaphthalene) and the electron-donating nature of 4,4’-disubstituted 2,2’-bipyridyl ligands. The complex with the 1,8-diazanaphthalene exhibits a shorter RhII-RhII bond and irreversible redox events at higher potentials compared to the other members of the series. Increasing the electron-donating ability of the bipyridyl ligand lowered the potential required for the metal-based oxidation event albeit with a loss in full reversibility.
Partial paddlewheel dirhodium(II,II) complexes with the electron-donating 2-oxy-6-methylpyridinate ligand and either the electron-withdrawing dipyrido[3,2-a:2’,3’-c]phenazine (dppz) or benzo[i]dipyrido[3,2-a:2’,3’-h]quinoxaline (dppn) ligand were synthesized and their potential to act as photodynamic anticancer therapy agents was tested in vitro. While both absorb visible range light, only the dppn containing complex is photocytotoxic against ovarian cancer cells. The work reported herein highlights the tunability of dirhodium complexes towards multiple applications through careful ligand field design. | en |
