Abstract
Bimolecular processes are ubiquitous in liquid-phase chemistry. A detailed understanding of their dynamics is pivotal to control and tune the reaction outcome, which, in turn, is essential to develop novel methodologies. Photochemically activated bimolecular reactions constitute an ideal field of study for ultrafast time-resolved spectroscopies, and this thesis demonstrates their successful application to three very different examples of reactions, that occur on vastly different timescales.The dynamics of an excited-state proton transfer (ESPT) reaction between a coumarin derivative and a methyl-imidazole model system were definitively and unequivocally characterized using ultrafast transient-absorption (TA) and time-resolved infrared (TRIR) spectroscopies. Density functional theory calculations were used to assign the observed spectroscopic features. The timescale for the ESPT was found to be ~1 ps.
The early steps of an hydrocarboxylation reaction making direct use of CO2 with styrenes have been studied with TA spectroscopy. The reaction relied on using a catalyst species, p-terphenyl (pTP), that was photoexcited and accepted an electron from a sacrificial amine electron donor. After having observed and clarified that pTP relaxation involves the release of torsional strain in the excited state on a timescale of several picoseconds, the electron-transfer reaction in ethanol was found to be diffusion limited, returning a rate constant of 7.80(± 1.99)×109 M-1s-1 and occurring at a contact radius of 0.68 ± 0.17 nm.
A novel artificial biohybrid system was synthesised and investigated with time-resolved spectroscopies to prove electronic energy transfer occurred between constituent quantum-dots (QDs) nanocrystals and a genetically modified mutant (3Hβ) of photosynthetic bacterial reaction-centre (RC) moieties. In such materials, where QDs act as an assembly hub and as artificial light harvesters, and RCs performs efficient charge-separation, energy transfer from the dots to the protein was found to occur with a time constant of 26.6 ± 0.1 ns and an efficiency of 0.75 ± 0.01.
| Date of Award | 2 Dec 2021 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Tom Oliver (Supervisor) & Andrew J Orr-Ewing (Supervisor) |