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The Effect of Metal Containing Ligands on The Metal-Metal Quadruple Bond: Structure, Synthesis, And Photophysics

Durr, Christopher Blair
http://rave.ohiolink.edu/etdc/view?acc_num=osu1429542171

Abstract Details

2015, Doctor of Philosophy, Ohio State University, Chemistry.
The world’s ever increasing demand for fossil fuels has lead to a renewed focus by the scientific community to develop energy sources that are clean, renewable, and economical. One of the most promising emerging technologies is photovoltaic cells that can turn sunlight directly into energy or into fuels such as methane or hydrogen. In order for these cells to replace preexisting energy sources, it is necessary to increase their efficiency and processability while also curtailing cost. The focus of this work will be on electron donating materials, the main purpose of which is to absorb light and cause charge transfer to occur in the cell. To increase efficiency of donor materials several factors must be considered. Firstly, the material must capture as much of the solar spectrum as possible, which ranges from 400 nm to well over 1200 nm. Thus a material that has a broad, tunable absorption band is key to capturing as much of this light as possible. Secondly, the absorbing material must efficiently absorb photons by having a high molar absorptivity. Lastly, when light hits the donor material there must be a sufficient separation of the electron-hole pair. The material must stay in this charge separated state long enough to undergo charge transfer to an acceptor and thus begin the circuit. M2 quadruply bonded complexes, where M2 = Mo2, MoW or W2 have optical properties ideal for electron donating materials. Compounds of this type have a fully allowed metal-to-ligand charge-transfer (MLCT) band that is tunable from 400 nm to 1200 nm based on the choice of metal and ligand. This absorption is quite intense with extinction coefficients from 20,000 to nearly 100,000 M-1cm-1. The MLCT is caused by the transfer of an electron from a M2d orbital to a ligand based p* orbital. The molecule exists in this singlet MLCT state for 3 – 25 ps before intersystem crossing to either a 3dd* or 3MLCT state lasting from 2 ns - >75 µs. This work will discuss the synthesis, characterization and photophysics of M2 complexes and their interactions with metal containing ligands. By using organometallic or metal-organic ligands it is possible to cover more of the solar spectrum as the metal containing ligands chosen also have allowable optical transitions that are possible to tune. The ligands discussed herein contain chromium, rhenium, and platinum which each have interesting photophysical properties of their own. In the initial chapters metal carbonyls of chromium and rhenium were studied as the CO infrared stretches served as markers to follow using femtosecond time-resolved infrared spectroscopy. The effect of additional metal d-orbitals on the molecules excited state dynamics was discussed in detail for these compounds. A theoretical study of M2-Pt acetylide polymers was also conducted to determine the electronic structure and optical properties of future materials. Isonicotinic N-oxide is investigated as a ligand for Mo2 systems and the resulting complexes are attached to solid state films consisting of TiO2, NiO and Indium-Tin oxide. Finally, the solid state packing of Mo2 halobenzoate complexes is discussed as molecules of this form tend to form interesting halogen-halogen interactions.
Malcolm Chisholm, Ph.D (Advisor)
Claudia Turro, Ph.D (Committee Member)
Patrick Woodward, Ph.D (Committee Member)
245 p.
Chemistry
Chemistry; Metal-Metal Bonding; Crystallography; Photovoltaics; Inorganic Synthesis; Density Functional Theory

Recommended Citations

Citations

  • Durr, C. B. (2015). The Effect of Metal Containing Ligands on The Metal-Metal Quadruple Bond: Structure, Synthesis, And Photophysics [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1429542171

    APA Style (7th edition)

  • Durr, Christopher. The Effect of Metal Containing Ligands on The Metal-Metal Quadruple Bond: Structure, Synthesis, And Photophysics. 2015. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1429542171.

    MLA Style (8th edition)

  • Durr, Christopher. "The Effect of Metal Containing Ligands on The Metal-Metal Quadruple Bond: Structure, Synthesis, And Photophysics." Doctoral dissertation, Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1429542171

    Chicago Manual of Style (17th edition)

osu1429542171
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This open access ETD is published by The Ohio State University and OhioLINK.