Beames, JosephAldawood, Fatimah2025-07-202025-07-18https://hdl.handle.net/20.500.14154/75911This PhD thesis describes the development of analytical processes for investigating a variety of novel luminescent organic compounds through modern spectroscopy techniques and computational chemistry approaches, as detailed in Chapters 3, 4, and 5. Also, this thesis chapter 6 focuses on designing a Herriot cell specifically for Mid-Infrared Spectroscopy (MIR) of transient species.Spectroscopy is a fundamental technique utilised by chemists to investigate and understand new compounds by analysing their interactions with electromagnetic radiation, including light. Steady-state absorption and emission spectroscopy, as traditional optical techniques, are useful for characterising photostable compounds and conducting constitutional analyses of samples before and after reactions by observing how molecules interact with light. These approaches, however, present limitations in analysing intermediates and excited states of reactions. To address this problem, transient spectroscopy techniques are methodologies used to examine the dynamics of excited states in molecules, typically involving pump-probe measurements to initiate a photochemical or photophysical process and observe it as a function of wavelength and time. These methodologies enable measurements of the lifetime for which it remains in this state before returning to its ground state. By analysing this process with such measurements, vital information about energy levels, durations of excited states, and their fundamental features can be extracted that are critical for understanding chemical reactions and properties. In this work, transient spectroscopic techniques are employed to examine and analyse novel organic compounds. Firstly, I analysed the spectroscopic properties of novel bichromophoric naphthalimide derivatives and sulfonated organic compounds synthesised by the Buurma group at Cardiff University using time-resolved spectroscopic techniques alongside computational chemistry approaches. These compounds exhibited thermally activated delayed fluorescence (TADF). It was found that the degree of TADF emitted by these species is very sensitive to the molecular design of the two chromophores and the distance between them. Similar techniques were employed to analyse novel dicationic and cationic radical compounds supplied by the Champness group to understand and investigate their stabilities and their bond dissociation processes. Our work suggests that the heavy atom-doped cationic naphthalenediimides (NDIs) are remarkably photostable with long-lived triplet states for use in photocatalysis and photosynthesis within metal-organic frameworks (MOFs); however, the radical cations readily decompose. Finally, a gas-phase multi-pass absorption spectrometer has been designed to analyse compounds in the mid-infrared, with a particular view to the analysis of radical transient species such as Criegee intermediates molecular analysis.221enUV-Vis and IR spectroscopy.Thesis