Photochemistry and Photophysics of Octahedral Ruthenium Complexes

The photo-induced ligand loss of the complexes [Ru(tpy)(AN)₃]²⁺ and cis-[Ru(tpy)(AN)₂Cl]⁺ (tpy = 2,2`:6`2``-terpyridine) and [Ru(tpy)(5CNU)₃]²⁺ was studied in water and in CH₂Cl₂ in the presence of chloride from tetrabutylammonium chloride (TBACl). [Ru(tpy)(5CNU)₃]²⁺ is not soluble in CH₂Cl₂. Photolysis in CH₂Cl₂ in the presence of chloride ions leads to the dichloro photoproduct trans-[Ru(tpy)(AN)Cl₂], and photolysis in water led to the diaqua photoproduct trans-[Ru(tpy)(AN)(H2O)₂]²⁺ or trans-[Ru(tpy)(5CNU)(H2O)₂]²⁺. The two axial ligands are replaced, while the equatorial ligand remains coordinated to the metal. For cis-[Ru(tpy)(AN)₃]²⁺ and [Ru(tpy)(5CNU)₃]²⁺ the axial ligands were replaced in a step-wise fashion, forming an intermediate with one axial acetonitrile ligand. All three complexes were shown to bind to DNA upon photolysis by gel electrophoresis, but not in the absence of light, indicating potential as anti-tumor agents for use in photodynamic therapy (PDT). cis-[Ru(tpy)(AN)₂Cl]⁺ has a higher quantum yield of ligand substitution and a lower energy metal to ligand charge transfer (MLCT) transition showing binding to DNA when irradiated at 650 nm, within the ideal PDT window of 600-850 nm.The low temperature emission and photolysis of [Ru(bpy)₃]²⁺, cis-[Ru(bpy)₂(AN)₂]²⁺, cis-[Ru(bpy)₂(MeBN)₂]²⁺, and cis-[Ru(bpy)₂(py)₂]²⁺ was studied to explore their excited state properties. The emission of [Ru(bpy)₃]²⁺ is known to take place from the ³MLCT state, with a temperature dependence resulting from a thermally accessible non-emissive triplet ligand field state higher in energy than the ³MLCT state. A decrease in emission quantum yield and comparable increase in the quantum yield of photolysis is observed for [Ru(bpy)₃]²⁺ with increasing temperature. This behavior led to the conclusion that the population of the ³LF from the ³MLCT state preceded photosubstitution. The temperature dependence of the emission of the related compounds cis-[Ru(bpy)₂L₂]²⁺, where L is AN, MeBN and py, was found to be different from the temperature dependence of the photolysis, suggesting that the photosubstitution proceeds through a different mechanism. One possibility is that the ³LF state is populated directly from the initially excited state and does not require population through the ³MLCT state.

Name thesis:degree_name

Doctor of Philosophy

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Chemistry

Grantor dc:publisher

The Ohio State University

Year dc:date

2013

Author dc:creator

• Sgambellone, Mark Allan

Contributors dc:contributor

• Turro, Claudia

• Chemistry
• Ruthenium
• photolysis
• photochemistry
• Photodynamic Therapy
• PDT

Statement dc:rights

• unrestricted
• This thesis or dissertation is protected by copyright: some rights reserved. It is licensed for use under a Creative Commons license. Specific terms and permissions are available from this document's record in the OhioLINK ETD Center.

Language dc:language

English

Repository record dc:identifier

http://rave.ohiolink.edu/etdc/view?acc_num=osu1366111201

OAI identifier oai:identifier

oai:etd.ohiolink.edu:osu1366111201