Dynamic Molecular Catalysts Based on Molecular Photoswitches

Saha, Monochura (2020) Dynamic Molecular Catalysts Based on Molecular Photoswitches. PhD thesis, Indian Institute of Science Education and Research Kolkata.

Text (PhD thesis of Monochura Saha (15RS044)) 15RS044.pdf - Submitted Version Restricted to Repository staff only Download (11MB)

Abstract

This thesis deals with synthesis, characterization and studies of activities of several novel photochromic compounds. Chapter 1 deals with the general introduction on the broad area of photochemistry and applications of various photochromic systems related to my research based on recent literature reports. Chapter 2 comprises of the synthesis of nine-membered cyclic azobenzene system and the studies of its photophysical property. Interestingly, this is the first report in the literature to show that a cyclic azobenzenecan display the switching of its fluorescence behaviour. Chapter 3 describes the switching of conductance using silver(I) ions with the nine-membered cyclic azobenzene. In the presence of the metal ions, the sulfur-containing system forms a one-dimensional polymer having the cyclic azobenzenes coordinated to silver ions that are bridged by the nitrate counterions. Hence it can be used as photoswitchable molecular wire. Chapter 4 deals with photoregulated carbonic anhydrase mimic using an imidazole-appended azo benzene compound. In the presence of a cationic polymer, we have demonstrated that the CA-activity could be enhanced by stabilzing the oxy-anionic transition state with the cis-form of the enzyme mimic which can catalyze the hydration of gaseous CO2.This is the first example of a photo modulated carbonic anhydrase active site mimic. Chapter 5 includes a photo regulated racemase mimic. The racemase enzymes convert L-amino acids to its D-isomer. The reaction proceeds through a general acid general base deprotonation-reprotonation mechanism assisted by a pyridoxal phosphate (PLP) coenzyme. This work reports a PLP coenzyme-photoswitch-imidazole triad where the racemization reaction can be controlled using light by tweaking the distance between the basic residue and the reaction centre.

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