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Synthesis, characterisation and complexation of phenylenebis(oxamates) and related ligands
MacLeod, Murray
THESIS 7941 The research presented in this thesis lies within the general area of supramolecular and coordination chemistry. The work herein can be divided into two distinct areas. Firstly, the syntheses and structural characterisation of o-phenylenebis(oxamides) and related ligands are described and secondly, the preparation and characterisation of novel transition metal complexes incorporating some of these ligands is reported. Chapter 2 details the synthesis of novel ligands that are related to o-phenylenebis(oxamate) L1, C14N2O6H16: (L1), C12N2O6H12 (L2), C12N4O4H14 (L3), C15N2O6H18 (L4), C13N4O4H16 (L5), C16N2O6H20 (L6), C14N4O4H18 (L7), C14N2O6H16 (L8), C14N2O6H16 (L9), C21N2O6H22 (L10) and C30N5O4H52 (L22)]. The structural description of hydrogen bonding within phenylenebis(oxamides) and related ligands is unreported in the literature. The crystallisation and single crystal X-ray diffraction studies of ligands L1 to L10 and L22 have resulted in the determination of nine novel crystal structures. Hydrogen bonding is present in all eleven molecules and is described using graph-set notation. Using this notation, the dimensionality of the supramolecular architectures is compared directly. The study has shown that the modification of the phenylenebis(oxamide) ligand framework leads to the formation of hydrogen bonded networks of varying dimensionality: zero-dimensional (L1 and L4), one-dimensional (L6, L7, L8, L10 and L22), two-dimensional (L2, L5 and L9) and three-dimensional (L3). The different dimensionality of the networks can be attributed to the different functional groups present on the ligands and the level of substitution of the aromatic ring. The diethyl ester oxamic ester structures (L1, L4 and L6) are of lower dimensionality than their N,N’-phenylenebis(oxamides) equivalents (L3, L5 and L7). L3 forms an unique infinite three-dimensional 66 network, L5 has an infinite two-dimensional (4,4) net structure and L7 forms an infinite one-dimensional ladder. Assemblies of higher dimensionality are achieved upon the change in substitution position of the oxamic acid esters. Movement from ortho- (L1) to meta- (L8) to para- (L9) results in the increase in dimensionality from zero- to one- to two-dimensions, respectively. The dimensionality of the supramolecular system can be disrupted by the deprotonation of the ligand and the introduction of a bulky cation, as evident from the structure of L22. The syntheses, structural characterisation and physical properties of transition-metal complexes of L1, L4 and L6 are presented in Chapter 3. The synthesis of the sodium salts of copper(II) complexes of L1, L4 and L6 resulted in the formation of [Na]2[Cu(L1)]⋅7H2O (1), [Na]2[Cu(L4)]⋅7H2O (4) and [Na]2[{Cu(L6)}(H2O)5]·2H2O (7). The crystal structure of 7 is presented herein and consists of a two-dimensional architecture. The metatheses of 1, 4 and 7 with tetraphenylphosphonium bromide yielded the complexes [PPh4]2[Cu(L1)] (2), [PPh4]2[Cu(L4)] (5), and [Na]2[PPh4]2[Cu(L6)]2·7.1H2O (8), respectively. The structures of 2 and 5 consist of discrete [Cu(L)]2- units (where L = L1 or L4) and tetraphenylphosphonium cations. The elucidation of the structure of 8 showed that the complete metathesis was not achieved. However, the formation of one-dimensional sodium-copper chains, where L6 is coordinated to the copper atom in a tetradentate manner with tetraphenylphosphonium cations within the lattice, had resulted. These chains are hydrogen bonded together through lattice water molecules which themselves are arranged in hexameric chains throughout the crystal lattice. The syntheses of manganese-copper chains, where the L1, L4 and L6 are coordinated to the copper atom, are presented. The crystallisation of [MnCu(L1)(H2O)3] (3) was not successful but the structural characterisation of [MnCu(L4)(H2O)3]⋅4H2O (6) and [MnCu(L6)(H2O)3]⋅4H2O (9) was. These exhibit unique hydrogen bonding between the ten water molecules, that reside between the chains, with butterfly topology. This thesis presents the first ever crystallographic evidence for this low energy arrangement of ten water molecules. 6 and 9 display identical ferrimagnetic behaviour and low temperature maxima in the magnetic moment (μeff) at around 10 K. Upon complete dehydration, 6 behaves as a metamagnet with a critical field of approximately 1kOe.
Keyword(s): Chemistry, Ph.D.; Ph.D. Trinity College Dublin
Publication Date:
Type: Doctoral thesis
Peer-Reviewed: Unknown
Language(s): English
Institution: Trinity College Dublin
Citation(s): Murray MacLeod, 'Synthesis, characterisation and complexation of phenylenebis(oxamates) and related ligands', [thesis], Trinity College (Dublin, Ireland). School of Chemistry, 2005, pp 191
Publisher(s): Trinity College (Dublin, Ireland). School of Chemistry
Supervisor(s): Kruger, Paul E.
First Indexed: 2017-09-14 06:51:22 Last Updated: 2020-07-28 08:26:43