Public Thesis Defense of Qian QIN - IMCN

Chiral sequence-defined oligomers for self-assembly and catalysis by Qian QIN

Lundi 17 mars 2025 à 10h00 – Salle de Serres OCEAN B002, 1 Croix du Sud à 1348 Louvain-la-Neuve

Catalysis is a crucial method for accelerating chemical reactions. In enzymes, the various chemical groups involved in the catalytic site assemble in spatially close positions, leading to optimal stoichiometry for a concerted action. In this context, the goal of this thesis was to design precision oligomers capable to spontaneously self-assemble into supramolecules having a series of synergistic catalytic groups positioned in a reactive pocket designed for the aerobic oxidation of alcohols. For this, sequence-defined poly(triazole-carbamate) oligomeric chains of controlled chirality, equipped with a variety of functional groups, were synthesized. To drive the assembly of the catalytic pocket, two base pairs, guanine (G)/cytosine (C) and 2,6-diaminopyridine derivative (D)/thymine (T), were individually inserted at the ends of two oligomeric strands (hereafter denoted as Oa and Ob). Furthermore, hydrophobic hexyl side-chains (C6) were added at the very end of the chains for improved solubility of the individual chains and stabilization of the assemblies. Then, cooperative catalytic groups, including Tempo (2,2,6,6-tetramethylpiperidinyl-1-oxy, M), pyridine (P) and imidazole (I), were distributed between the two complementary oligomers with different distributions being tested. Whereas Oa always consisted of a C6GMPTC6 sequence, three complementary strands were made, Ob1 (C6CI’IPDC6 sequence), Ob2 (C6CIIDC6 sequence) or Ob3 (C6CIPDC6 sequence). These complementary chains self-assembled into a dynamic library of poly(oligomers) and their catalytic activity was investigated on a range of alcohols. In the dynamic library, di(oligomeric) cycles were found to strongly dominate the catalytic behavior, especially at low dilutions, provided the two chains together comprise all the needed elements for catalysis as was the case for the Oa/Ob1 system. In contrast, the absence of a single cooperative catalytic group led to a significant drop in catalytic activity, as was the case for the Oa/Ob2 and Oa/Ob3 systems. The formation of stable di(oligomeric) cycles was demonstrated by NMR diffusion experiments and could be reproduced by a mathematical model involving the many equilibrium equations existing in the dynamic library. The model also allowed us to predict the catalytic properties and to identify key requirements for improving further the catalytic activity.
Jury members:
Prof. Alain Jonas (UCLouvain, BE), supervisor
Prof. Karine Glinel (UCLouvain, BE), supervisor
Prof. Jean-François Gohy (UCLouvain, BE), chairperson
Prof. Charles-André Fustin (UCLouvain, BE), secretary
Prof. Anja Palmans (Tu/e, NL)
Dr. Antony Fernandes (Certech, BE)
Dr. Jie Li (BUCT, CHN)
Pay attention: the public defense of Qian QIN will also take place in the form of a videoconference.