1. SELF-SORTING OF DYNAMIC IMINE LIBRARIES UNDER CHEMICAL AND PHYSICAL STIMULI; 2. CHARACTERIZATION OF POROUS MATERIALS BASED ON A FLUORINATED TETRAZOLE
Hsu, Chia-Wei 1984-
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Chapter 1 introduces the self-sorting processes of dynamic combinaotrial libraries (DCLs) under thermodynamic and kinetic control. Based on the concept of dynamic combinatorial chemistry (DCC), disulfide exchange, imino bond formation, transesterification, and metal-ligand interaction are widely utilized to perform the re-equilibration of molecules. Simplification of multicomponent systems and the manipulation toward the direction of equilibrium are reviewed. Chapter 2 of this dissertation describes an application of a new external stimulus—adsorption on the silica gel surface—to dynamic imine libraries constructed of as many as four aldehydes and four anilines. During the elution process, imines keep trading their components, resulting in the amplification of the least polar imine which travels down the silica gel-based column the fastest. This process is then iteratively repeated to isolate the next least-polar component in the remaining imine library, eventually simplifying the library from n2 into n members. In Chapter 3, we demonstrated iterative simplification of a dynamic imine library constructed from 10 aldehydes and 10 anilines using three orthogonal external stimuli. First, mild oxidation (using molecular iodine as an oxidant) was applied to oxidize the most electron rich imine with the rapid imine exchange. In the second self-sorting step, we obtained a halogenated [2×2] sub-system with bromo- and chloro-substituted imines from the imine library. Third and final step was a slow distillation of the residual imines from the column, leading to the amplification of the least volatile imine in 61% yield. Ultimately, this [10×10] imine library is simplified into two major products and one sub-system after iterative self-sorting. Chapter 4 will describe the synthesis and characterization of a porous material based on an extensively fluorinated aromatic tristetrazole. This molecule crystallizes in a porous structure which is held together through [N−H…H] hydrogen bonds and electrostatic interactions between C–F units in these molecules. This porous material is compositionally stable up to 270 °C and shows selective adsorption of CO2 over N2 (15:1 in mmol g−1) at 195 K and 760 mmHg.