Calixarene transition metal and crown ether based anion and ion-pair receptors
The aim of this thesis is to develop novel receptors for the recognition of anions and ion-pairs. The guest binding and sensing properties of the receptors are studied by spectroscopic and electrochemical techniques. The ion-pair receptors described herein incorporate amide or urea functionalities for anion binding and crown ether moieties for alkali metal cation complexation. In addition, many receptors contain redox- and/or photo-active groups capable of sensing guest binding events. Chapter One introduces the field of supramolecular chemistry. A review of synthetic cation, anion and ion-pair receptors reported in the literature is undertaken, and the formation of selfassembled architectures is discussed. Chapter Two details the synthesis and study of a range of new upper-rim functionalised calixarene anion and ion-pair receptors. The anion and ion-pair binding and sensing properties of the receptors are investigated by ¹H NMR spectroscopy, electrochemistry and luminescence spectroscopy. Two ion-pair receptors display a positive cooperative ion-pair effect, whereby the presence of potassium cations causes an enhancement in the strength of anion binding via electrostatic interactions and conformational effects. Chapter Three centres on ion-pair receptors incorporating an azacrown group for alkali metal cation complexation together with amide functionalities for anion binding. Receptors containing either ferrocene or transition metal dithiocarbamate groups are capable of electrochemically and/or optically sensing the binding of anionic guests. Chapter Four describes disulphide-appended receptors designed for self-assembly onto gold surfaces. A ferrocene- and disulphide-appended calixarene receptor incorporating hydrogen bonding moieties forms self-assembled monolayers on gold electrodes which exhibit a surface sensing amplification in the electrochemical recognition of anions. In addition, the assembly of receptors onto gold nanoparticles is explored with the aim of producing UV-VIS spectroscopic sensors for guest binding. Chapter Five reports the experimental procedures and characterisation for all products. The Appendices provide information on experimental techniques, list the crystallographic data and summarise all the receptors studied.