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Dithiocarbamate, Cubanedicarboxylate and Mixed Ligand Coordination Polymers
thesis
posted on 2017-04-23, 22:41 authored by Emily Jane MensforthNovel coordination
polymers have been synthesised and characterized by single crystal diffraction
methods. The potential of these networks as gas storage materials has been
examined by gas sorption analysis where possible.
Chapter two describes the preparation and characterisation of coordination complexes containing the dithiocarbamate ligand piperazine-dithiocarbamate. A series of complexes were prepared through the in situ preparation of the ligand when reacted with alkaline earth metal salts. Monomeric, dimeric or polymeric complexes were prepared depending on the reaction solvent, and/or the inclusion of non-bridging coligands.
Chapter three expands upon the findings from chapter two, with polymeric piperazine-dithiocarbamate complexes prepared through the inclusion of the bridging coligands 4,4’-bipyridine-dioxide and pyrazine-dioxide. The propensity for alkaline earth metals to coordinate to oxygen-donor species was exploited whilst continuing to examine the varied coordination motifs possible by piperazine-dithiocarbamate. Two 2D networks were prepared where the network was a result of the 4,4’-bipyridine-dioxide connections, while the third complex was 3D with both the pyrazine-dioxide and the piperazine-dithiocarbamate ligands bridging within the framework.
Chapter four examines the potential of the aliphatic ligand 1,4-cubanedicarboxylic acid to act as a building block within a porous coordination polymer. The analogous nature of this ligand to 1,4-benzenedicarboxylic acid was confirmed through the synthesis of a cubic network analogous to MOF-5. Whilst the complex was highly disordered crystallographically, the similarities to MOF-5 were reinforced by the gas sorption analysis. The cubane analogue of MOF-5, Zn4O(1,4-cdc)3, has an exceptional enthalpy of adsorption of 7.5 kJ mol-1, and a H2 uptake of 210 cm3 g−1 at 77 K and 1250 mbar, equal to a maximum storage capacity of 1.9 wt %.
The predisposition of the 1,4-cubanedicarboxylic ligand towards crystallographic disorder was highlighted by another three mixed ligand frameworks which were prepared from reactions with cobalt and 2,4,6-tri(4-pyridyl)-1,3,5-triazine. While two of the three networks formed were 3D in nature and the crystallography indicated porous channels were present, the inability to isolate these materials purely in high yield prevented additional gas sorption analysis being carried out.
Chapter five expanded on the mixed ligand approach by combining 2,4,6-tri(4-pyridyl)-1,3,5-triazine with isophthalic acid derivatives. The inclusion of various functional groups at the five-position of the isophthalic acid ligand did not impact the structures significantly. However, a change in reaction conditions, from solvothermal to slow evaporation, produced a novel 3D network which was vastly different to the networks solvothermally.
Chapter six explored the effects of replacing the isopthalic acid co-ligand with for the slightly longer 2,6-naphthalenedicarboxylic acid. When a series of reactions were conducted with 2,4,6-tri(4-pyridyl)-1,3,5-triazine and either zinc nitrate or cobalt nitrate four novel 3D networks were produced. Minor synthetic changes resulted in two zinc complexes with the same network topology, with subtle differences in ligand binding modes within the network separating the two. The two cobalt networks were obtained from the one reaction, with both frameworks displaying highly porous 3D networks, although the inability to synthesis these frameworks purely again prevented gas sorption analysis.
Chapter two describes the preparation and characterisation of coordination complexes containing the dithiocarbamate ligand piperazine-dithiocarbamate. A series of complexes were prepared through the in situ preparation of the ligand when reacted with alkaline earth metal salts. Monomeric, dimeric or polymeric complexes were prepared depending on the reaction solvent, and/or the inclusion of non-bridging coligands.
Chapter three expands upon the findings from chapter two, with polymeric piperazine-dithiocarbamate complexes prepared through the inclusion of the bridging coligands 4,4’-bipyridine-dioxide and pyrazine-dioxide. The propensity for alkaline earth metals to coordinate to oxygen-donor species was exploited whilst continuing to examine the varied coordination motifs possible by piperazine-dithiocarbamate. Two 2D networks were prepared where the network was a result of the 4,4’-bipyridine-dioxide connections, while the third complex was 3D with both the pyrazine-dioxide and the piperazine-dithiocarbamate ligands bridging within the framework.
Chapter four examines the potential of the aliphatic ligand 1,4-cubanedicarboxylic acid to act as a building block within a porous coordination polymer. The analogous nature of this ligand to 1,4-benzenedicarboxylic acid was confirmed through the synthesis of a cubic network analogous to MOF-5. Whilst the complex was highly disordered crystallographically, the similarities to MOF-5 were reinforced by the gas sorption analysis. The cubane analogue of MOF-5, Zn4O(1,4-cdc)3, has an exceptional enthalpy of adsorption of 7.5 kJ mol-1, and a H2 uptake of 210 cm3 g−1 at 77 K and 1250 mbar, equal to a maximum storage capacity of 1.9 wt %.
The predisposition of the 1,4-cubanedicarboxylic ligand towards crystallographic disorder was highlighted by another three mixed ligand frameworks which were prepared from reactions with cobalt and 2,4,6-tri(4-pyridyl)-1,3,5-triazine. While two of the three networks formed were 3D in nature and the crystallography indicated porous channels were present, the inability to isolate these materials purely in high yield prevented additional gas sorption analysis being carried out.
Chapter five expanded on the mixed ligand approach by combining 2,4,6-tri(4-pyridyl)-1,3,5-triazine with isophthalic acid derivatives. The inclusion of various functional groups at the five-position of the isophthalic acid ligand did not impact the structures significantly. However, a change in reaction conditions, from solvothermal to slow evaporation, produced a novel 3D network which was vastly different to the networks solvothermally.
Chapter six explored the effects of replacing the isopthalic acid co-ligand with for the slightly longer 2,6-naphthalenedicarboxylic acid. When a series of reactions were conducted with 2,4,6-tri(4-pyridyl)-1,3,5-triazine and either zinc nitrate or cobalt nitrate four novel 3D networks were produced. Minor synthetic changes resulted in two zinc complexes with the same network topology, with subtle differences in ligand binding modes within the network separating the two. The two cobalt networks were obtained from the one reaction, with both frameworks displaying highly porous 3D networks, although the inability to synthesis these frameworks purely again prevented gas sorption analysis.
