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Spectroscopic Studies of Mixed Valence Compounds and Confined Fluorphores

  • Author(s): Chen, Yen-Ting
  • Advisor(s): Zink, Jeffrey I
  • et al.

The work presented in this dissertation encompasses spectroscopic research in two different areas. The first part involves spectroscopic studies of mixed valence systems. Mixed valence compounds have two or more equivalent charge bearing sites that are coupled, and can occur in both the ground and excited state. An intervalence charge transfer band can be observed for the former, while the latter can have two transitions whose intensities depend on selection rules.

The first chapter in this dissertation presents an introduction to the fundamental concepts of mixed valence, and the spectroscopic and theoretical methods that can be utilized to study mixed valence systems. The following chapter analyzes the excited state mixed valence of cis and trans di-(4-acetylpyridine)-tetraamineruthenium complexes using absorption and resonance Raman spectroscopies, the time-dependent theory of spectroscopy, and neighboring orbital models. The intricacy of the importance of dipole orientation averaging is also discussed. The next chapter presents an expansion of the three state model used for transition dipole moment analysis that has been previously used. The expanded model is discussed for both the ruthenium complex and a diisopropyl ditolylhydrazine compound. Chapter four investigates another mixed valence system, a cyclophane diradical dication compound that has ground state mixed valence. This system has an unusual form of coupling, mediated through pi-pi interaction between two stacking phenyl rings.

The second part of this dissertation and the last chapter investigate the physical characteristics of a fluorophore confined in the pores of azobenzene-functionalized mesoporous silica nanoparticles. Two spectroscopic methods are utilized: time-resolved fluorescence anisotropy and rigidochromic studies. These studies help elucidate the microenvironment inside of the mesopores.

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