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Spectroscopic and Kinetic Characterization of Photochromic Ruthenium Chelating Sulfoxide Complexes

McClure, Beth Anne
http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1286471945

Abstract Details

2010, Doctor of Philosophy (PhD), Ohio University, Chemistry and Biochemistry (Arts and Sciences).
Complexes of the type [Ru(bpy)2(OSOR)]+, where OSOR is a sulfinyl benzoate chelate with various substituents, R, attached to the sulfur, and [Ru(bpy)2(pySO)]2+, (pySO = 2-(isopropylsulfinylmethyl)pyridine) were synthesized and characterized by a number of spectroscopic techniques. Structural characterization was done by 1H NMR and IR spectroscopy as well as X-ray crystallography for some complexes. Analysis of the structural features such as S-O bond lengths and ν(S=O) vibrational stretches are suggestive of a π-back bonding interaction between the ruthenium metal center and the sulfoxide group in the S-bonded isomer. Electrochemical measurements also support such an interaction by large positive Ru2+/3+ reduction potentials for the S-bonded isomer. Cyclic voltammetry reveals irreversible oxidation behavior that agrees with previous studies finding an S-to-O isomerization to occur after oxidation to the Ru3+ state. However, compared to similar non-chelate ruthenium sulfoxides, the rate of isomerization is significantly slower indicating that the chelate hinders the degrees of freedom utilized in this reaction. Electronic absorption spectra are also consistent with a stabilization of the dπ orbitals as a result of π-back bonding, especially as compared to similar non-chelate sulfoxide complexes. Irradiation of the complexes was found to promote an S-to-O isomerization. The complex [Ru(bpy)2(pySO)]2+ was found to undergo reversible O-to-S phototriggered isomerization as well which is very rare for transition metal based photochromes. Analysis of the UV-Vis absorption and low temperature emission spectra of these complexes reveal significant distortion of nuclear coordinates between the ground state potential energy surface and the Franck-Condon state and lowest energy excited state potential energy surfaces. Emission spectral fitting indicates strong vibronic coupling between a vibrational mode similar in energy to the ν(S=O) mode with relaxation to the ground state. Transient absorption measurements indicate rapid non-adiabatic isomerization from a MLCT state of S-bonded or η2-SO character to the O-bonded ground state, with time constants of isomerization as fast as 84 ps. The complex O-[Ru(bpy)2(pySO)]2+ shows a similar reverse isomerization with relaxation to the S-bonded ground state as well. The non-adiabatic mechanism is consistent with the large distortion indicated by spectral analysis, further supporting an η2-SO geometry for the excited state minimum geometry.
Jeffrey Rack, Ph D (Committee Chair)
P. Gregory Van Patten, Ph D (Committee Member)
Michael Jensen, Ph D (Committee Member)
Eric Stinaff, Ph D (Committee Member)
219 p.
Chemistry
photochromic; ruthenium; sulfoxide; spectral characterization; isomerization; kinetics

Recommended Citations

Citations

  • McClure, B. A. (2010). Spectroscopic and Kinetic Characterization of Photochromic Ruthenium Chelating Sulfoxide Complexes [Doctoral dissertation, Ohio University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1286471945

    APA Style (7th edition)

  • McClure, Beth Anne. Spectroscopic and Kinetic Characterization of Photochromic Ruthenium Chelating Sulfoxide Complexes. 2010. Ohio University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1286471945.

    MLA Style (8th edition)

  • McClure, Beth Anne. "Spectroscopic and Kinetic Characterization of Photochromic Ruthenium Chelating Sulfoxide Complexes." Doctoral dissertation, Ohio University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1286471945

    Chicago Manual of Style (17th edition)

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This open access ETD is published by Ohio University and OhioLINK.