Coordination Polymers for Chiroptical Control

Abstract

Stimuli-responsive chiroptical properties are critical for the next generation of security, sensing, and data storage materials. Coordination polymers (CPs) and metal-organic frameworks (MOFs) are prime materials to study structure-property relationships regarding chiroptical switching responses due to their crystalline, designable structures. This thesis aims to design, synthesise and characterise chiral, stimuli-responsive CPs and MOFs to investigate the origins of chiroptical switching properties.

The structural effect on a photoreduction process in two chiral MOFs based on Zn2+ and Cd2+ were investigated. Each MOF has vastly different structures, due to the sizes of the component metal ions, and the orientation of and distance between their photoactive ligands. Their ability to act as chiroptical switches was dependent on their structure’s ability to facilitate chiral induction into new optical transitions within the material.

A chiral Cd-based MOF comprising of co-facial Py2TTF was investigated to exploit its potential of dual responsivity. The material showed changes in chiroptical response based on the [2+2] photocyclisation response and the chemical oxidation of the component TTF cores, demonstrating its ability to act as a multi-stimuli responsive sensor.

Three fluorescent, chiral, Pr-based CPs with varying hydration levels were synthesised and characterised. The materials showed varied chiroptical responses attributed to their structure and water content. Eu and Er analogues of the most hydrated CP were generated, showing varied chiroptical responses due to the identity of the metal ion. The chiroptical response in the Eu CP was sensitised to the uptake of anthracene.

This thesis exemplifies the relationship between chemical structure, chiroptical response and sensitivity towards different stimuli. The understanding of chiroptical control gained through this work is an important contribution to the area of chiroptically switching materials.