This thesis describes the synthesis and crystallisation of a selection of known and novel transition-metal – nitrite complexes and their detailed study using non-ambient X-ray diffraction techniques. These coordination compounds are specifically investigated for their ability to undergo nitro – nitrito linkage isomerisation in the single-crystal, with conversion between isomers achieved on either thermal- or photoactivation. The lifetime of the excited-state isomer is strongly dependent on the experimental temperature and, as such, this thesis is also concerned with time-resolved crystallographic methods. This work relies primarily on the technique of photocrystallography, a growing area of crystallographic research that has enjoyed considerable interest in recent decades.Chapter 1 reviews the seminal progress made in both time-resolved and photocrystallographic research, made possible by dramatic technological advances in the field in recent decades.Chapter 2 outlines the goals of this research project, aiming to obtain a more detailed understanding of the factors that influence the solid-state nitro – nitrito isomerisation.Chapter 3 describes the X-ray methods used in these studies, introducing both fundamental crystallographic principles and detailing the experimental procedures that are undertaken. Chapters 4 and 5 record steady-state photocrystallographic studies conducted for a series of complexes containing bulky, chelating ancillary ligands accompanying a monodentate nitrite group expected to be capable of nitro – nitrito isomerism. The response of these systems to both thermal- and photoactivation is investigated via single-crystal diffraction methods. The analysis focusses on the potential steric and electronic influences from the surrounding crystalline environment, which may have an impact on the progress of the solid-state reaction.Chapter 6 introduces photocystallographic kinetic methods to investigate the progress of nitro – nitrito conversion in real time. These studies are the first of their kind to be conducted on nitrite linkage isomer species and some novel methodology is introduced.Finally, Chapter 7 discusses pseudo-steady-state and trial time-resolved experiments conducted using the new time-resolved diffraction set-up on Beamline I19 at the Diamond Light Source. These early results indicate the power of time-resolved methods for elucidating key information on the nitro – nitrito conversion process and show promise for future experiments.
|Date of Award||13 Jun 2014|
|Supervisor||Paul Raithby (Supervisor)|