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Magnetic Resonance Studies of Iron Spin Crossover Complexes and their Cobalt Analogs

Marts, Amy Renae

Abstract Details

2013, Doctor of Philosophy, Miami University, Chemistry and Biochemistry.
Spin crossover is a physical phenomenon that occurs when the metal center in a complex has more than one stable electron configuration. Complexes of this type are typically characterized in the solid state for their potential applications in display devices, digital memory, and sensors. This dissertation consists of four chapters that investigate solution NMR relaxation enhancements in spin crossover-related complexes of Fe(II), Co(II) and Zn(II). Chapter 2 presents paramagnetic relaxation enhancements of Co(II) bis-trispyrazolylmethane in comparison to previously reported studies on Co(II) bis-trispyrazolylborate. Electron spin relaxation rates extracted from the individual measurement of the proton relaxation enhancements show structural dynamics occur at a higher temperature range in the trispyrazolylmethane complex. Often the counterion identity of spin crossover complexes affects the behavior of the metal center. In the case of [Fe(bpp)2]+2, the counterion has been shown to promote or inhibit spin transition. Chapters 3 and 4 are focused on determining how an anion not coordinated to the metal center can have such an effect. Chapter 3 presents a full solution characterization of the Co(II) analogs of bispyrazolylpyridine complexes to obtain a reference of thermal effects in the absence of spin crossover behavior. In this chapter, solution UV-vis, EPR, and NMR relaxation measurements of [Co(bpp)2]X2 (bpp=2,6-bis(pyrazol-1-yl)pyridine; X= BF4-, PF6-) are presented. Chapter 4 probes the relaxation of the counterion nuclei within bpp chelates using the relaxation measurements for solution distance calculations. Comparison of relaxation measurements of chelates containing paramagnetic, diamagnetic, and spin crossover active metal centers shows the BF4- counterion is more tightly associated than the PF6- counterion in solution. Variable-temperature proton NMR of the Fe(II) chelates reveals that, although it is not spin crossover active in solid state, [Fe(bpp)2][PF6]2 is spin crossover active in solution. Chapter 5 investigates complexes of the scorpionate family, presenting 1H, 2H, 11B and 13C relaxation measurements of natural abundance and isotopically-labeled trispyrazolylborate (Tp) and trispyrazolylmethane (Tpm) chelates of Co(II) and Zn(II). The relationship between paramagnetic and quadrupolar relaxation enhancements is characterized by comparison of the paramagnetic and diamagnetic analogs.
David Tierney, PhD (Advisor)
Michael Crowder, PhD (Committee Chair)
Robert McCarrick, PhD (Committee Member)
Gary Lorigan, PhD (Committee Member)
Elisabeth Widom, PhD (Committee Member)
146 p.

Recommended Citations

Citations

  • Marts, A. R. (2013). Magnetic Resonance Studies of Iron Spin Crossover Complexes and their Cobalt Analogs [Doctoral dissertation, Miami University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=miami1385033230

    APA Style (7th edition)

  • Marts, Amy. Magnetic Resonance Studies of Iron Spin Crossover Complexes and their Cobalt Analogs. 2013. Miami University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=miami1385033230.

    MLA Style (8th edition)

  • Marts, Amy. "Magnetic Resonance Studies of Iron Spin Crossover Complexes and their Cobalt Analogs." Doctoral dissertation, Miami University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=miami1385033230

    Chicago Manual of Style (17th edition)