Exploring the Functionality and Application of Cyclic Phosphazanes

Abstract

In this thesis the application of, and various synthetic routes to novel cyclodiphosphazanes were reported. Applications towards building blocks of macrocyclic structures, electrochemically active ligands for inorganic electrolytes, and chiral discrimination reagents for enantiomeric amines were explored.

Firstly, the extensive versatility of cyclodiphosphazanes in synthesising P(III), P(V), or mixed-valence inorganic macrocycles is demonstrated in this thesis. Despite many of the macrocycles we report here being air- and moisture-sensitive, oxidation of P(III) to P(V) with peroxide, elemental sulphur, or selenium can be used to address this issue. Additionally, the host-guest chemistry of these macrocycles with anionic guests and transition metal complexes was studied.

Secondly, a series of phenylene-diamino cyclodiphosphazanes (both P(III) and P(V)) and investigated the electrochemical properties via cyclic voltammetry was synthesised. Though irreversible processes were observed in the target molecules and the fact that the complete synthesis of the suite of electrolytes was not completed due to the limited time frame, we believe there is still much to explore in this area and some suggestions for future work were given in the corresponding chapter.

Lastly, in the research regarding cyclic phosphazanes as chiral sensors, an easily accessible chiral inorganic reagent through simple synthetic steps with commercially available components was developed. One can determine the enantiomeric excess at ease by reacting the reagent with chiral amines. Promising results were also obtained from thorough studies of 1D and 2D proton NMR.

Throughout these projects, the likely roles of cyclodiphosphazanes in interdisciplinary research was explored.