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Browsing by Subject "Vibrational spectroscopy"

Now showing 1 - 2 of 2
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    Dynamics, Solvent, and Reactions: Ultrafast Infrared Spectroscopy of Vaska's Complex and its Adducts
    (2015-02) Jones, Brynna
    This thesis describes and interprets experiments using two-dimensional infrared spectroscopy (2D-IR) and infrared pump-probe spectroscopy (IPP) as applied to the organometallic catalyst Vaska's complex (VC) and its I2 and O2 adducts (VC-I2 and VC-O2 respectively) in a variety of solvation environments. The IPP observations yield information about the speed of vibrational relaxation and how it changes as the solvent is altered, giving suggestions as to the mechanism of the relaxation of vibrational energy. The 2D-IR experiments give information about the dynamics occurring in the solvation shell of the solute molecules and specifics about the molecular origins of the lineshapes found in linear infrared spectroscopy (FTIR). These studies are presented in light of possible connections between solvent dynamics and chemical reaction rates occurring in those solvents. The solvation dynamics of VC and VC-O2 are characterized by 2D-IR first in 3 neat solvents. 2D-IR spectra were analyzed using the inverse center line slope (CLS) as a representative of the frequency-frequency correlation function (FFCF). The dynamics are compared to previously determined oxidative addition rate constants. Next, an IPP and linear infrared spectroscopic study was performed on VC-I2 and VC-O2 in two different sets of binary solvent mixtures. The vibrational lifetime changes linearly with solvent composition. Evidence that relaxation proceeds directly into the solvent modes is shown. In the third study presented, 2D-IR was performed on the VC-I2 vibrational mode to dissect the linear lineshape into its homogeneous and inhomogeneous contributions in binary solvent mixtures of either chloroform or benzyl alcohol in d6-benzene. The full FFCF was determined. Inhomogeneous dynamics are implicated as the dominant broadening mechanism. Finally, an IPP, 2D-IR, and kinetics study on VC and VC-O2 in binary solvent mixtures of d6-benzene with chloroform and benzyl alcohol is presented. The vibrational lifetimes for VC, in contrast to VC-O2 and VC-I2, show a decrease with increasing mole fraction of the more polar solvent in both sets of mixtures. There is evidence of correlation between the rate constants and the homogeneous linewidth of VC-O2, as well as its inhomogeneous amplitude.
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    Two-Dimensional Infrared Vibrational Echo Spectroscopy Measurements of the Structural Dynamics Occurring in Conducting Polymer Thin Films.
    (2011-09) Eigner, Audrey Ann
    The research presented in this thesis is concerned with the elucidation of the origin of structural dynamics and their relationship to charge mobility in conducting polymer systems. In the past thirty years, research in the field of electrically conducting polymers has grown immensely. Interest in such polymers is due mainly to their unique semiconducting properties and thus their potential application in plastic electronics. While it is known that the charge transport of such polymers is linked to their molecular structure, very little is known about the relationship between charge transport and structural dynamics. In particular, this work has focused on the conducting polymers poly(3-hexylthiophene) (P3HT) and polyaniline (PANI). Samples of each polymer were studied using two-dimensional infrared vibrational echo spectroscopy (2D-IR VES), as well as one-dimensional infrared, UV-visible, and fluorescence spectroscopies. Additional characterizations of the polymers were performed, and included transmission electron microscopy (TEM), hole-mobility and resistance measurements. The vibrational echo technique was especially well suited for this study because it removed inhomogeneous broadening and allowed for the monitoring of the time evolution of molecular structure on the picosecond time scale. Viewed together, the studies presented in this work have begun to correlate specific structural dynamics with changes in the film conductivities.