Synthesis, Characterization And Applications Of A Conformationally Switchable Fluorescent Oligophenol Foldamer As An Ion Receptor For Selective Sensing Of Copper(Ⅱ) Ions

Helically or circularly folded aromatic foldamers have continuously attracted considerable interests over the past decades since the pioneering work using multiple-center H-bonding systems to direct the intramolecular folding of aromatic pyridine-based backbones by Hamilton and co-workers in 1994. Concurrent with the elaboration of their wide-ranging structures, these H-bonded aromatic foldmers have been demonstrated to perform highly variable functions including reaction catalysis, controllable molecular motion, reactive sieving, solvent gelating, ion transportation, stabilization of G-quadruplex structures, and selective recognition of both ionic and neutral species. Nevertheless, the hitherto developed diverse classes of H-bonded aromatic folamers mostly lack the structure-switching ability, and so perform their pre-designed functions without significant conformational changes in their molecular backbones. In other words, H-bonded aromatic backbones containing switchable units have been studied comparatively much less, and no study on the use of metal ions to trigger the conformational changes of these H-bonded aromatic foldamers for selectively sensing certain metal ions has been reported. The H-bonded foldamer molecules endowed with "switchable" functions are undoubtedly of great interests in the creation of advanced adaptive bio-and nanomaterials and molecular sensing devices for such as environmental monitoring of toxic molecular species including metal ions.The main purpose of this thesis focus on chemical modifications of phenol and pyridone-based monomers, along with the constructions of certain conformational switchable aromatic folding oligomers and their potential on metal ions recognition.The key aspects of this thesis are described below:1. By using certain chemical modifications such as:alkylation, ester hydrolysis, Curtius rearrangement to obtain t-Bu protected amines from acids, and the critical approach of thiolation by using the Lawesson’s reagent to form the thiolated pyridone-based monomers and further more to obtain the high-leveled folding oligomers through the coupling reactions of the amino acids. For such reactions, the optimizations of conditions via mechanistic analysis have been carried out to optimize the reaction yields.2. Deep research on the metal ions-mediated deprotonation and protonation of both phenol-based and methoxy phenol-based aromatic monomers, further to obtain the conformational switching via computational chemistry related work. In conclusion, to obtain the key information of the chemical structure and interior-curve ratios and so on, which in order to find the potential of metal ion binding ability of certain building blocks.3. Chemical coupling of the amide aromatic monomers to afford both linear and helical oligomers of variable structures, proper modification of deprotonation with certain positions of the phenol hydroxyl group to derive the conformational switching along with the strong coordination of metal ions which result in fluorescence quenching. For the first time, we have demonstrated that the amine and metal ions-mediated deprotonation of certain aromatic foldamers could lead to the conformational switching of the structures and the differences in fluorescence quenching ability of various metal ions could in return reach the goal of selective recognition of certain metal ions.