Synthesis and Spectroscopic Studies of Phototunable Receptors for Host–Guest Interactions

Rahaman, Sk. Atiur (2019) Synthesis and Spectroscopic Studies of Phototunable Receptors for Host–Guest Interactions. PhD thesis, Indian Institute of Science Education and Research Kolkata.

Text (PhD thesis of Sk. Atiur Rahaman (14RS026)) 14RS026.pdf - Submitted Version Restricted to Repository staff only Download (6MB)

Abstract

This thesis on the broad area of supramolecular chemistry addresses research problems of designing receptor and sensor systems with an aim of using some of them for real-life applications. The introductory Chapter 1 reviews the existing literature reports. Chapter 2 deals with tuning the size of the binding pocket and the binding affinity of a triazole-based bipodal anthracene host towards the anionic guests, such as the benzoate ion. The receptor can be tuned by light. The host molecule exploits the C–H***X interaction motif. The photocycloaddition of the receptor wrecks the framework of the anthracene and closes the binding pocket. The reverse photoisomerization process is achieved by 254 nm light in the presence of the benzoate ion. Chapter 3 reports a fluorescent probe for oxygen based on the oxygen-induced polymerization of a thiol via formation of disulfide linkages. A main reason for the contamination of packaged food is the presence of oxygen because it helps the growth of moulds and microorganisms. This TPE-based system can detect molecular oxygen with a 100 fold enhancement of emission intensity via the formation of a polymer with disulfide linkages. We have demonstrated the efficacy of this probe in the form of test-strips for the detection of oxygen in packaged containing cheese samples. This offers a possibility of using the compound to detect leakages in food packages. Chapter 4 describes a significant progress in sensing cyanide with fluorescent molecular probes. We have created a unimolecular sensor using simple synthetic approach by combining biocompatible tryptophan moiety to an activated aldehyde functionality with a dithiocarbamate linkage that can specifically interact with cyanide and consequently, generate a distinct optical output. This property enables it to determine the cyanide in various biological samples. This ratiometric fluorescent sensor can detect the cyanides both in absorption and emission modes. We have detected cyanide in seafood with this probe in the aqueous medium with a detection limit of 2.01 ppb. Chapter 5 includes the preparation of a simple thiocarbamate probe that contains a 10π electronic system. The probe displays a high selectivity for Hg²⁺ ions. On complexation with Hg²⁺, an aryl C–H bond of the ligand is activated, and forms a C–Hg bond. The sulphur and nitrogen donors coordinate with another Hg²⁺ ion forming a one-dimensional crystalline network. This removes Hg2+ ions from contaminated water samples.

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