Nietalloporphyríns and related tetra -azamacrocyclic complexes
fulfil a wide range of bioactive roles. They are employed
extensively in electron -transfer catalytic cycles and
as such they can exist in a variety of oxidation states.
The work presented in this thesis is devoted to a study
of the redox properties of series of model transition - metal porphyrin and porphyrin -like complexes.
Detailed voltammetric studies have uniquely enabled us
to evaluate the importance of back -bonding from the metal
to the chelating ligand. In addition, in situ spectroelectrochemical techniques, incorporating both electronic
absorption spectroscopy and ESR spectroscopy, have allowed
us to unambiguously assign the electron- transfer step
occurring as a metal -based or macrocycle -based redox couple.
A rationalisation of the electronic spectral properties
of the electrode products is presented. A re- examination
of the electrochemistry of some iron and ruthenium
porphyrins leads us to disagree, to a significant extent,
with previous reports. We also discuss in detail the
redox properties of a series of metallochlorins and utilise
the results to explain the spectroelectrochemical behaviour
of bonellin, a most remarkable naturally occurring macro-cycle.