Effects of shape, conformation, and symmetry on macrocycle synthesis via alkyne metathesis

dynamic covalent chemistry;conjugated macrocycle;alkyne metathesis;depolymerization;arylene-ethynylene macrocycle

Sisco, Scott

关键词: dynamic covalent chemistry;    conjugated macrocycle;    alkyne metathesis;    depolymerization;    arylene-ethynylene macrocycle;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/49822/Scott_Sisco.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

The well-defined shapes and π-systems of conjugated macrocycles enable systematic modulation of these structures for self-assembly into functional organic materials. However, most synthetic methods rely on kinetically controlled reactions that often afford complex mixtures and low yields of a desired macrocycle. Dynamic covalent chemistry (DCC), specifically alkyne metathesis, was used to elucidate and probe the structural parameters that favor efficient macrocycle synthesis, because it involves rapid, reversible reactions under thermodynamic control, yielding product distributions that are determined by the differences in free energy of the possible product structures. This dynamic approach is fairly predictive for conformationally constrained and C2-symmetric monomers, but when the monomer structure deviates from these parameters, it becomes difficult to predict the major product and the factors that favor a narrow distribution over a broad distribution of products.Since competing structures must possess distinct differences in molecular geometry or conformation to realize narrow product distributions and high yields of a single macrocycle target via DCC, monomer structures were rationally designed to determine the influence of various factors on dynamic macrocyclization. Specifically, this work involves the synthesis of structurally unique poly(arylene-ethynylene)s that undergo alkyne metathesis-mediated depolymerization. The effects of three structural properties on the distribution of macrocycles from alkyne metathesis were investigated: shape (Chapter 2), conformation (Chapter 3), and symmetry (Chapter 4). Collectively, these results demonstrate the profound influence of an incongruent monomer shape to favor a narrow distribution of directional macrocycles, the effect of torsional axes in the efficient preparation of functionalized macrocycles with relaxed conformational constraints, and the roles of entropy and symmetry in the self-sorting of chiral macrocycles. This work is an important step toward establishing design rules for the rational synthesis of complex, functional macrocycles by showing how small changes in structural parameters influence the equilibrium and product distribution. Development of these guidelines is advantageous for the efficient preparation of single macrocycle targets by thermodynamic controlled approaches, allowing for exploration of the potential applications and fascinating properties of conjugated macrocycles.