Understanding the molecular interactions that control chemical processes is essential for developing novel advancements in any chemical industry, especially for the fields of surface modifications and photoactive chemical reagents. Monolayers and thin films are essential to a wide range of surface chemistry and materials science applications, such as chemical separations, heterogeneous catalysis, and tribology. However, adlayers currently utilized have fixed properties upon deposition onto substrates. Alternatively, photoactive reagents, specifically super-photobases, are pivotal for controlling the temporal and spatial extents of photochemical reactions used in industries such as precision chemistry and high-speed chemical sensing. Nonetheless, few known super-photobases currently exist, and little is understood about the molecular dynamics that give rise to such reactive properties upon photoexcitation. As such, this two-part work focused on the characterization of metal ion-complexed films as candidates for the creation of films with reversible properties, as well as the investigation of the excited-state behavior and spectral dynamics of super-photobase precursor molecules.The first part of this work focused on the study of the molecular properties that lead to the robustness of Cu2+-complexed amphiphilic Langmuir-Blodgett films. Incorporation of Cu2+ ions into the film system resulted in the unique formation of a highly ordered, rigid film system resistant to collapse. Film orientation and mobility were determined to be controlled by Cu2+-amphiphile interactions and a shift in dominating intermolecular forces as subphase pH increased. The unique presence of a rigid film at high surface pressures and pH conditions was attributed to the extrusion of Cu2+-amphiphile moieties into the aqueous subphase rather than traditional amphiphile buckling, which occurs at low pH conditions. In the second part of this work, the excited-state behavior of FR0, a substituted fluorene precursor to the recently developed super-photobase FR0-SB, was studied to determine the state-dependent solvent-solute interactions that give rise to the unique reactivity of the photobase molecule upon photoexcitation (ΔpKb ~ 15). Using time-resolved fluorescence spectroscopy and quantum chemical calculations, the electronic structure and relaxation dynamics of FR0 were examined in protic and aprotic solvents. Hydrogen-bonding interactions in protic solvents, particularly those in the S2 excited state, were determined to mediate relaxation dynamics. Solvent hydroxyl functionality concentration was also determined to play a role in such dynamics. Examination of the behaviors of structurally modified versions of FR0 demonstrated that the spectral dynamics observed for FR0 are structurally invariant, but that the nature of hydrogen bonding changes depending on the placement and type of modification. Overall, this work has led to a fundamental characterization of unique classes of surface modifications and photoactivated chemical reagents. First, the dynamics leading to unusually robust thin films were determined, the understanding of which can lead to the creation of selective interfaces using such films. Second, the intermolecular interactions lending themselves to unique spectral properties of super-photobase precursor molecules were identified, which can serve as a vantage point for the future synthesis and development of additional photobase compounds. In both aspects of this work, such advancements contribute to the furthering of each field by providing important fundamental frameworks for future applications in surface chemistry and photoactive reaction chemistry.
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