Ruthenium Mesoionic Carbene Complexes and their Applications in Energy Generation and Storage
Abstract
A series of bis(tridentate) ruthenium complexes bearing 2',6'-bis(1-(2,6-dimethyl-4-bromophenyl)-3-methyl-1,2,3-triazol-4-yl-5-idene)pyridine (C^N^C) have been synthesized and characterized. The complexes of the type [Ru(terpy)(C^N^C)]2+ and derivatives herein, exhibit longer excited state lifetimes (τ) than the archetypical [Ru(terpy)2]2+ (terpy = 2,2':6,2''-terpyridine; τ = 0.25 ns) by several orders of magnitude (τ ~ 8 μs). Their unique ligand geometry and robust sensitization of TiO2 offer insightful design considerations in both dye-sensitized solar cell (DSSC) and water oxidation.
In Chapter 2, a series of ruthenium complexes were investigated for their emission properties, which exhibited some of the longest room temperature excited state lifetimes ever reported. Modifications of both ligand fragments were conducted with electron-donating groups and electron-withdrawing groups, which enabled fine-tuning of the triplet metal-to-ligand charge transfer (3MLCT) state. This was a result of destabilizing the normally thermally accessible deactivating triplet metal centered (3MC) state. The location of the lowest-unoccupied molecular orbital (LUMO) could be tuned to reside on either the terpy or C^N^C fragment through chemical modification.
Chapter 3 provides details on the sensitization of TiO2 through the cooperative anchoring of phosphonate (-PO3H2) and carboxylate (-CO2H) groups and their performance in the DSSC. Using a combination of anchoring groups provided an opportunity to address the instability due to hydrolysis with the -PO3H2 group, while maintaining electronic communication through the preferred -CO2H. The geometry of the two tridentate ligands within the complexes permitted them to be bind through both ligands to the TiO2 surface. Temporal stability studies identified the cooperative binding approach successfully increased hydrolysis resistance and that the –CO2H moiety on the terpy ligand was critical for higher power conversion efficiencies (PCE ~ 0.2%). The absorption spectrum showed modest absorptions over the visible spectrum 400 to 650 nm (λmax ~ 470 nm ; ε up to 1.0 × 104 M-1cm-1), which limited the maximum PCE ~ 2% based on the solar spectrum.
In Chapter 4, the cooperative anchoring strategy was exploited in the heterogenization of a molecular water oxidation catalyst. The title complex ([Ru(bpy-CO2H)(C^N^C-PO3H2)Cl]2+) investigated was anchored to TiO2 and the catalytic oxidation of water (~4.0 μA/cm2; TOF 0.0004s-1) was demonstrated.
Description
Keywords
Education--Sciences, Chemistry, Chemistry--Inorganic
Citation
Brown, D. (2017). Ruthenium Mesoionic Carbene Complexes and their Applications in Energy Generation and Storage (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/27698