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Title: Electrochemical and spectroelectrochemical studies of 2,2'-bipyridine derivatives as coordination ligands with transition metals
Author: Al-Musharafi, Salma Khamis
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2006
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This thesis is concerned with the synthesis, electrochemistry and spectroelectrochemistry of three different types of 2,2’-bipyridine ligands; the 5,5’-(X)2-bpys, (bpy = 2,2’-bipyridine)(5,5’-Br2-bpy, 5,5’-Cl2-bpy, 5,5’-Ph2-bpy and 5,5’-(CO2R)2-bpy (where is R is Et and Me) were reinvestigated, the chloro substituted-2,2’-bipyridines (5,5’-Cl2-bpy, 6,6’-Cl2-bpy and 4-Cl-bpy) and the nitro substituted bpys(4-NO2-4’-Cl-bpy, 4,4’-(NO2)2-6,6’Cl2-bpy 2-Cl-4-NO2-py and 4,4’-(NO2)2-bpy was reinvestigated. The Pt(II) complexes of these ligands were also studied. 5,5’-Cl2-bpy and 4-Cl-bpy found to undergo one irreversible reduction. The reversibility of the one-electron reduction of 6,6’-Cl2-bpy can be affected by temperature and scan rate. The electron reduction is delocalised over the two pyridine rings with a contribution from the chloro-substituent. [Pt(5,5’-Cl2-bpy)Cl2] and [Pt(4-Cl-bpy)Cl2] undergo one reversible reduction. Due to the instability of [Pt(4-Cl-bpy)Cl2] the complexes could not be studied spectroelectrochemically. However, in-situ UV/Vis/nir and EPR experiments of [Pt(5,5’-Cl2-bpy)Cl2] revealed that the electron reduction is ligand based. 5,5’-Ph2-bpy showed one reversible reduction. The redox chemistry of 5,5’-Ph2-bpy can be explained by the reduction electron delocalised over the whole two py rings with a large contribution from the 2,2’ and 5,5’ carbon atoms. In complexation [Pt(5,5’-Ph2-bpy)Cl2] undergo two reversible one electron reductions, Pt(II) found to force the ligand to be planar, thus the electron reduction is delocalised over the bpy hence the LUMO is ligand based. 5,5’-Br2-bpy revealed one irreversible reduction, however, the Pt(II) complex of this ligand showed one reversible reduction. In-situ UV/Vis/nir and EPR in line with related complexes such as [Pt(Me)2-bpy)Cl2] showed that the contribution of the Pt to the SOMO is in the range 8-13% and confirm that the reduction electron enters a ligand based orbital. The crystal structures of 5,5’-Cl2-bpy and 6,6’-Cl2-bpy are both reported.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available