A crystallographic study of coordination polymers

Abstract

The focus of the research described in this thesis is the synthesis and structural characterisation of compounds that are structurally related to the [Cu2(benzoate)4(pyrazine)]n coordination polymer, which has been shown to have reversible gas adsorbing properties. As single-crystal X-ray diffraction is the primary characterisation technique used in this study, the theory behind this method is presented in Chapter 1. This chapter also provides a general review of linear coordination polymers of the type [Tr(ArCOO)4(NRN)]n¬ as a prelude to the investigations reported in the following chapters and where Tr signifies transition metal and NRN a bifunctional amine ligand. Chapter 2 reports on the synthesis and structural characterisation of [Cu2(benzoate)4(DABCO)]n and [Cu2(phenylpropiolate)4(pyrazine)]n along with a comparison with the previously published [Cu2(benzoate)4(pyrazine)]n and [Cu2(phenylpropiolate)4(DABCO)]n structures. The study establishes that while both the new compounds have some of the components needed to provide the flexibility needed for reversible gas adsorption, ultimately both have features in their crystal packing, which rules this out. Chapter 3 focuses on the synthesis and structural characterisation of analogues of [Cu2(benzoate)4(pyrazine)]n in which the benzoate had been replaced by each of the three ortho substituted benzoates, bromo, iodo and acetyl. These are shown to belong to the same structural type as the parent unsubstituted benzoate so that they have the potential to reversibly adsorb gaseous molecules. The ortho substituent impinges on the crystal regions that would accommodate a guest molecule so that substitution offers a means of tuning selectivity (Jayasinghe, Salzman and Forbes, 2016). Chapter 4 extends the study to cobalt paddle-wheels comoplexe and presents the structure of the [Cu2(ortho-iodobenzoate)4(DABCO)]n paddle wheel coordination polymer, which belongs to the same structural type as the copper paddle wheel polymers described in chapter 3. A second type of paddle-wheel polymer is also reported, [Co2(ortho-acetylbenzoate)4]n in which acetyl oxygen atoms form adjacent paddle-wheels from the caps instead of the intended pyrazine. Finally, the research results are drawn together as a conclusion in Chapter 5, which also includes some suggestions for further research

Date of Award	1 Aug 2019
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Robin Pritchard (Supervisor)