A supramolecular approach to generating functional materials using organic cages and macrocycles

Supramolecular chemistry, also known as the “chemistry beyond the molecule”, is the fundamental underlying concept explaining the enzyme-substrate lock-and-key process and, the double helix structure of DNA. It centers on the non-covalent and reversible interactions between molecules and how they specifically assemble into larger, more intricate and sophisticated assemblies. With an in depth understanding of this field of chemistry, molecules have been designed and engineered to possess specific functional groups which allow the manipulation of non-covalent interactions and endow the molecule with particular properties tailored for a specific application. Hence, supramolecular chemistry has made possible the development of new smart and responsive materials used in various fields.

This dissertation explores the application of supramolecular struts, organic cages (OCs) and macrocycles (MCs), for industrial separation and biomedical needs. These OCs and MCs, with inherent functional properties contain built in pores that can accommodate guests of specific shapes, and sizes. The separation thrust of this work delves into the host-guest properties of these supramolecules and their potential as sorbents to separate and purify hydrocarbon mixtures. The fluorination of porous materials endows the system with enhanced stability, crystallinity and selective adsorption properties. A fluorine rich leaning pillararene with improved hydrophobicity, illustrates these claims by behaving as a molecular sieve having a superior affinity for benzene over cyclohexane (20:1). As an alternative method to separating xylene isomers, a non-porous polymorphic azobenzene cage is comprehensively studied. Interestingly, only para-xylene molecules possess the right shape and size to fit in the extrinsic pores of the system which is also favored by the non-covalent interactions between the host and guest molecules. Additionally, each of the aforementioned are unmatched in their respective separations. These groundbreaking findings are extremely encouraging in the development of new all organic sorbents aimed at addressing the energy intensive industrial challenges.

Conversely, in the biomedical area of this research, OCs and MCs are designed for the advancement of bioprobe technology for cellular imaging and sensing purposes. With the limitations of traditional fluorophores like BODIPY and cyanines, this dissertation introduces the concept of supramolecular improved fluorophores (SIFs). 2,1,3-Benzothiadiazole is an up-and-coming fluorophore being used in bioprobes design. This work presents an inherently endoplasmic reticulum selective BTD-based cage with superior fluorescent properties as a result of macrocyclization-induced emission enhancement. This cage also fluorescently flares ER stress in immune cells indicating inflammation. Subsequent undertaking showcases a cell permeating macrocycle (CPM) containing diketopyrrolopyrrole as a trackable and targetable drug delivery system. Owing to its self-assembly, CPM is able to passively diffuse into the cell while avoiding endosomal digestion and deliver undamaged biologics to the cytosol. Hence, SIFs represent a significant addition to the library of biological probes for enhanced intracellular selectivity, targetability and sensing.

Two ongoing projects discussed in this thesis intend to expanding and exploring chemical space. Firstly, the fluorinated pillararene is modified with a thiolate imparting the macrocycle with improved affinity for soft metals thus, opening the door for gold/silver nanoparticles functionalization for disease treatment. Lastly, biocompatible benzothiadiazole based triangular-shaped macrocycles are investigated. These exhibit fluorescence response to changes in polarity and viscosity, indicating application potential as subcellular sensors.


Chem Ph.D. Candidate Aliyah Fakim,  supervised by Prof. Niveen Khashab

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17 Jul, 2024
09:30 AM - 12:30 PM
B4, L5, R5209