Progress toward the synthesis of a biomimetic membrane, and, The study of cadmium sulfide Qdots: A possible photocatalyst for both the efficient reduction of aryl azides and the rational design of molecular-scale patterned surfaces.

摘要

To investigate the biosynthetic pathway of ubiquinone (Q) in its natural environment, the synthesis of key components of a biomimetic membrane were reported. The constituents of the membrane consist of a phosphonic acid 17, carboxylic acid 20, and two different ubiquinone precursors 21 + 52. The key step in the syntheses of the latter compounds was a Stille coupling between a synthesized allylic stannane and the corresponding aryl bromide. With both sufficient quantities and an efficient strategy to the mentioned compounds, the transformation of key intermediates along the ubiquinone biosynthetic pathway can be examined in the confines of a self-assembled monolayer. Ultimately, by varying the length of the lipid-ubiquinone construct, the active site of a particular enzyme binding site can be probed as a function of Q precursor chain length.; In chapter two, we describe a new, general approach for the selective reduction of aryl azides to the corresponding amines using ultra-violet radiation and CdS nanoparticles (CdS Qdots) as photocatalysts. Our strategy to reduce aryl azides combines the reactivity of both CdS nanoparticles and azides to gain access to aryl amines under neutral conditions. In sum, the results from this work show that nanoparticles have the potential to act as convenient photocatalysts for organic synthesis as the observed reduction was specific for azides only, occurred under neutral conditions, and produced easily purified products. In addition to the photo-reduction of aryl azides, the improved synthesis of a class of heterobifunctional photo-reactive crosslinkers, 4-azido-2-alkoxybenzaldehydes, was reported. Extensive employment of these compounds is now possible.; In chapter 3, we build upon this novel photocatalyzed, selective reduction of aryl azides using CdS nanoparticles to determine the feasibility of a fundamentally new approach for nano-patterning surfaces. This chapter serves to accomplish several essential tasks. First, we report the synthesis of a novel thiol terminated molecule with a headgroup comprising the azidobenzaldehyde linkage examined in Chapter 2. Using this thiol, we made self-assembled monolayers of the azide on gold substrates. Finally, we demonstrated surface photocatalytic reduction of the azide to the amine by CdS nanoparticles using FTIR spectroscopy and contact angle measurements.