Date of Graduation

12-2015

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Chemistry (PhD)

Degree Level

Graduate

Department

Chemistry & Biochemistry

Advisor

Bill Durham

Committee Member

Jingyi Chen

Second Committee Member

Ryan Tian

Third Committee Member

Colin Heyes

Keywords

Pure sciences; Chemistry; Inorganic; Photochemistry; Ruthenium

Abstract

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.

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.

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.

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.

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.

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