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Title: Physico-chemical studies of coordination complexes of the platinum group metals
Author: McInnes, Eric J. L.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1995
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This thesis is concerned with the electrochemistry and spectroscopy of redox-active late transition metal complexes of the 2,2'-bipyridine ligand (bpy) and their reduction products. Complexes of general formula [Ph(4,4'-X2-bby)L2] (where L is a non redox-active ligand and X = NH2, OEt, Me, H, Ph, C1, CO2Me) undergo two one-electron reductions as revealed by cyclic voltammetry. The absorption spectra of the one-electron reduction products reveal the first of these reductions to be localised on the bpy ligand giving rise to radical anion ligand complexes of Pt(II). Epr spectra of the reduced, seventeen-electron species indicate a significant (ca. 10%) admixture of metal 5d orbitals in the SOMO, in good agreement with EHMO calculations. Both the E1/2 value of the first reduction process and the MLCT νmax value vary linearly with the Hammett parameter of the substituent X. The second reduction electron spin-pairs with the first in the same π* orbital. The LUMO of [Pd(4,4'-X2-bpy)C12] is Pd 4d based and these complexes undergo irreversible two-electron reductions. Complexes of the 4,4'-(NO2)2-bpy ligand undergo up to four one-electron reductions. Epr spectroscopy of the di-reduction products of [M(4,4'-(NO2)2-bpy)L2] (M = Pd, Pt, L = C1; M = Rh, L2 = 1,5-cod) shows that spin-triplet species are formed on di-reduction and consequently that the LUMO-SLUMO gap is smaller than the spin-pairing energy for these complexes. The redox-active orbitals are highly localised on the nitro-groups. EHMO calculations are in good agreement. [Pt)bpy)2]2+ undergoes a redox-induced dimerisation reaction at room temperature. Low-temperature cyclic voltammetry reveals the redox-active orbital to be bpy-based. The single-crystal structures of [Pt(4,4'-(NO2)2-bpy)C12] and [Au(bpy)C12]BF4 are reported.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available