Photochemistry of a Series of Weakly Coupled Dinuclear Ruthenium(II) Complexes

<p>An improved synthetic method was developed for symmetric ruthenium(II) polypyridine complexes with the form L2Ru(diphen)RuL2. The scope of the reaction was investigated in regards to the ligands, bridging ligands, and starting materials. Several ligands were successful in the synthesis, including 2,2’-bipyridine (bpy), 4,4’-dimethyl-2,2’-dipyridyl (dmb), 1,10-phenanthroline (phen), 4,7-diphenyl-1,10-phenanthroline (dpphen), and 3,4,7,8-tetramethyl-1,10-phenanthroline (tmphen). Ligands that did not react to form symmetric dimeric complexes were 2,2’-bipyrazine, bpz, and 2,2’-bipyrimidine, bpm.</p> <p>Dpp, 2,3-bis(2-pyridyl)-pyrazine, effectively replaced diphen as the bridging ligand to produce (phen)2Ru(dpp)Ru(phen)24+. However, replacing the [Ru(CO)2Cl2]n with Ru(DMSO)4Cl2 did not prove successful. The newly developed synthesis was also applied to the synthesis of monomeric complexes with the form Ru(phen)L2 for comparison. The spectroscopic and electrochemical data collected for the dimeric complexes was similar to the data for the monomeric complexes indicating that the dimers are weakly coupled.</p> <p>The photochemistry of the complexes was then studied to confirm that the dimers were weakly coupled. UV-vis tracking of the reaction of (phen)2Ru(diphen)Ru(phen)24+ implied a photosubstitution reaction took place in which a phen ligand was replaced by bromines. Several failed attempts were made to replace the bromines with a ligand that would allow the complex to be analyzed via ESI-MS. The photosubstitution products were never identified.</p> <p>The photoredox reactions for the complexes were investigated as well. The effect of the oxidative quencher Fe3+ on the excited lifetimes of the complexes was analyzed. The kq values found for Ru(bpy)32+, Ru(phen)(bpy)22+, and (bpy)2Ru(diphen)Ru(bpy)24+ were all comparable. This supports the classification of the dimeric complexes used in this study as weakly coupled.</p> <p>The back reaction that follows the quenching reaction and the yield of the oxidized ruthenium complexes were studied. The determined kback values for both quenchers, Fe3+ and Cu2+, were in the expected range and similar among both the monomers and dimers. This suggests that the dimeric complexes are weakly coupled.</p>

Name thesis:degree_name

Doctor of Philosophy in Chemistry (PhD)

Level thesis:degree_level

Dissertation

Year dc:date.available

2015

Author dc:creator

• Puckett, Latisha Michelle

Advisor dc:contributor.advisor

• Durham, Bill

Contributors dc:contributor

• Chen, Jingyi
• Tian, Z. Ryan

• Pure sciences
• Chemistry
• Inorganic
• Photochemistry
• Ruthenium
• Inorganic Chemistry
• Physical Chemistry

Repository record dc:identifier

https://scholarworks.uark.edu/etd/1331

OAI identifier oai:identifier

oai:scholarworks.uark.edu:etd-2330