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Title: Synthesis of phosphonate chains, rings and polymers
Author: Cave, Dale
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2004
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This thesis reports the synthesis and characterisation of a series of compounds with [O3PCH2N(CH2CO2)2]4-, PMIDA. The ligand forms a very stable anionic complex with 3d metals e.g. Co(II), Fe(II)(III), Ni(II) as well as Zn(II). As well as the chelating interaction to the central metal, the ligand bridges to other metals thereby generating anionic networks. The effect which the charge-balancing alkali metal cations have on the shape and connectivity of the metal-ligand lattice has been investigated. The coordination number of geometry of the transition metal ion also has an effect. Reactions with a variety of cobalt and zinc sources yield materials containing the [ML]2- repeat unit. Simple chains in which the anionic moiety polymerises in a head-to-tail fashion were obtained for Li, Na, K and Cs. Materials have also been prepared in which the fragments polymerise to give rings with 3 repeat units (Na) and 6 repeat units (K and Rb). For Rb and Cs, compounds have also been isolated in which some of the ligands are completely deprotonated. These have the formula M3H(CoL)2 and consist of simple chains which dimerise via hydrogen bonding. Dimeric molecular species K11HM2L4 (M=Co, Ni) may be prepared when excess ligand salt is used. Reaction of ligand salt with a variety of sources of Fe yields materials which contain mixtures of Fe(II) and Fe(III). When the counterion is potassium, a ladder-like polymer K3.5Fe2L2 can be isolated. By altering the reaction stoichiometry it is possible to isolate K11(FeL)6 in which the ML moieties polymerise to form infinite sheets. Using Na or Rb as the counterion produces materials containing closely related structures Na11(FeL)6 and Rb10(FeL)6 which have the same connectivity but which crystallise in different space groups. The phosphonate groups in these materials bridge between three Fe and forming a triangle-based lattice. The magnetic behaviour of the Co- and Fe-containing materials has been investigated.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available