Physical properties and dynamics of hydrogen bonding and proton transfer compounds.

摘要

Hydrogen bonding and proton transfer are important chemical phenomena with applications to biological processes, such as DNA mutagenesis, and technology. Much of this important chemistry occurs in the solution phase. This research uses a combination of experimental and theoretical methods to examine the photophysical properties and dynamics of hydrogen-bonding and charge transfer compounds. There are three systems investigated: pyridylpyrroles, 1-acetylaminoanthraquinones and symmetrically substituted 1,5-anthraquinones. The structural properties of the pyridylpyrrole molecule, its dimer and complexes with alcohol are examined by computational methods and experimentally with nuclear magnetic resonance. These properties are related to the photophysical behavior of the species in different solvent environments. The 1-acetylaminoanthraquinones are examined with respect to their ability to facilitate excited state proton transfer, which can be controlled by the acyl substituent group and the choice of solvent environment. A new ultrafast laser spectroscopic technique is used to directly probe changes in the solvent response following photoexcitation of the solute. This provides a new and complimentary view of the solution phase reaction to previous investigations that probe spectroscopic transitions of the solute. The measurement is sensitive to both changes in the solute-solvent interactions following the chemical reaction and solvation, as well as the energy exchange that accompanies the reaction. The results are compared to the structural and energetic properties of the molecules as determined by static spectroscopy and theoretical calculations. Similarly two symmetrically substituted 1,5-anthraquinones are examined, one each that does and does not exhibit excited state proton transfer. This is a nondipolar system and provides a comparison to the 1-acetylaminoanthraquinone system in which the solvent-solute interactions are dominated by the dipole-dipole interactions. The cumulative focus of the research is upon the role of the inter- and intra-molecular interactions on the physical properties and dynamic behavior of the molecules in the solution phase.