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The platinum complex [Pt(4-CO₂CH₃-py)₂(mnt)] was synthesised and characterised. The acid analogue [Pt(4-CO₂H-py)₂(mnt)] was also prepared and tested in a dye-sensitised solar cell. An IPCE of 0.5% at 450 nm and a recombination half-life of 3.0 x 10^-2 s were obtained. These results were compared to the previously studied [Pt{4,4’-(CO₂H)-2,2’-bipy}(mnt)] and [Pt{3,3’-(CO₂CH₂CH₃)-2,2’-bipy} (mnt)] platinum dyes to see the influence of replacing the commonly used 2,2’-bipyridine ligand with two substituted pyridine ligands. An alternative [Pt(diimine)(dithiolate)] complex, [Pt(4-CO₂R-py)₂(dmit)], (where R = H and CH₃) was also synthesised, characterised and tested in a solar cell which had an IPCE of 0.7% at 450 nm. The nitropyridine platinum complex [Pt(4-NO₂-py)₂(mnt)] was prepared, characterised and tested in a solar cell. The nitro group replaced the more common acid linker group that binds a sensitiser to titania. This dye did sensitise to TiO₂ but not as effectively as the acid groups and was easily desorbed. An IPCE of 0.6% at 450 nm was obtained. The complex [Ru(4-CO₂R-py)₄Cl₂] (where R = H and CH₃) was synthesised, characterised and tested in a solar cell. This ruthenium-pyridyl complex gave high extinction coefficients in the visible region of 25,000 and 17,000 M^-1 cm^-1. The solar cell for this compound gave η = 5.8 x 10^-3% and an IPCE of 1.6% at 420 nm. Substituted pyridines with the general formula n-X-py, where X = NO₂, CO₂H, CN, CO₂CH₃, CO₂CH₂CH₃, Ph, NH₂ or CHO and n = 2, 3 or 4, were studied using electrochemistry and the effect of substitution group, substitution position and complexation to a metal centre on their E_1/2 potentials was determined. The effect of different solvents, and of water, on this potential was also investigated.

The design of luminescent lanthanide complexes is of great importance in the development of biological labelling systems providing effective alternatives to radioisotopes, and for their application as light triggered sensors and materials. Our approach involves the controlled formation of mixed-ligand Eu(III) and Tb(III) complexes based on specific molecular recognition such that a biological molecular recognition event may be detected. The strategy is based on design of lanthanide systems with controlled coordination around the metal ion. Enhancement of the emission is based on intramolecular energy transfer which is much more efficient than the FRET mechanism. Our design is based on the arrangement of two different ligands around the metal ion (Figure 1). (Fig. 1352) A multidentate non-absorbing ligand (NAL) is chosen to form a stable, coordinatively unsaturated complex with the metal, allowing one or two water molecules to occupy the vacant binding sites. Formation of the luminescent ternary complex is achieved by displacement of the remaining inner sphere water molecules upon recognition between the LnNAL chelate and a strongly absorbing, strongly binding light harvesting centre (LHC). This strategy allows flexibility in choosing the antenna ligand. The chromophore, which governs the input energy of light, need not be included in the structure of the encapsulating ligand. Complicated syntheses are avoided and the system can be optimised can be optimised for maximum emission output. We have chosen DTPA-AM₂ ligands as our NAL ligands and simple aromatic carboxylic acids as LHCs to test the design. The DTPA-AM₂ chelates the metal in an octandentate manner via the 3 nitrogen donors of the diethylenetriamine backbone, the two amide carbonyls and the three remaining carboxylate groups. The amide nitrogen atoms are not involved in coordination and are free to form a binding cavity, ideal for LHC recognition. The binding of the LnNAL chelate by the acid moiety is followed by monitoring the emission of the europium ion, triggered by intramolecular energy transfer from the LHC> Electrospray mass spectrometry data and NMR spectroscopic studies provide additional evidence of the controlled formation of ternary complexes. Specificity of molecular recognition is observed between EuDTPA-bis(ethylamide) and picolinic acid, phthalic acid and benzoic acid binding units, forming mixed ligand species in 1:1, 1:1 and 1:2 stoichiometries respectively.

Steady-state and time-resolved fluorescence spectroscopies have been used to investigate the photophysical properties of the fluorescent DNA base analogue, 2-aminopurine (2AP). For the first time, the fluorescence decay of 2AP is shown to be biexponential. In aqueous solution, 2AP has lifetimes of 11.0ns and 13.5ns, which are shown to decrease in less polar solvents. These two lifetimes are attributed to the N7-H and N9-H tautomers of 2AP. The fluorescence responses of ten 2AP labelled DNA duplexes have been recorded. The decays are fitted by four discrete components and all are dominated by a ~100ps component, which is consistent with efficient quenching of the 2AP by electron transfer from guanine. The fluorescence response of 2AP within the duplexes is sensitive to both the nature of the bases in its immediate vicinity and the extended nucleotide sequence. 2AP labelled DNA has been used as a probe of base flipping by the M.HhaI methyltransferase enzyme. The DNA was labelled such that duplexes with the 2AP adjacent to, opposite and at the target site for base flipping have been studied. Duplexes with the 2AP outside of the M.Hhal recognition sequence have also been investigated. When 2AP is the target base for flipping its fluorescence decay shows a significant response to enzyme binding. It is shown that this change in photophysical behaviour can be used as a definitive indicator of the base flipping mechanism. A similar response is also shown for the M.TaqI base flipping enzyme. Placing the 2AP at positions adjacent to and opposite the target base for flipping demonstrate the amazing selectivity, of HhaI for its target base and demonstrate the effectiveness of the enzyme’s stabilisation of the DNA duplex during base flipping.

Studies have been carried out in the following areas: (1) <i>Photochemistry</i> The photochemical behaviour of selected aromatic carbonyl compounds has been studied, especially in relation to the nature of the excited state involved in chemical reaction. The photochemistry of certain pyrimidine-based agrochemicals and related compounds has been investigated from a kinetic and product viewpoint. The dye sensitised photooxidation of these compounds has also been studied. (2) <i>Spectroscopy and Charge-Transfer Complexation</i> The spectroscopic properties and electron acceptor ability of a variety of organic compounds has been reported upon. (3) <i>Chemistry of Polynitroaromatic Compounds</i> The synthesis of a number of new polynitronaphthalenes and polynitro-acenaphthenes has been achieved, and the properties of many of these compounds has been studied by nmr, esr, electronic spectroscopy and by mass spectrometry. The reaction of base with such compounds has also been investigated. (4) <i>Education</i> Articles have been published in educational journals on molecular complexes, colour, solar energy and spectroscopy. Textbooks on molecular spectroscopy and photochemistry have been published.

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Since Norrish in the 1930's discovered the type I and type II photochemical reactions of ketones there have been numerous studies on both alkyl and aryl ketones. The photochemistry of β, y-epoxyketones has been little studied in contrast to the exhaustive studies with the photochemistry of α, βepoxyketones. A general mechanism has been suggested to explain photochemical reactions of β,Y-epoxyketones, which is not in full agreement with the results obtained during the photolysis of steroidal β,y-epoxyketones.

With increased interest in charge separated states formed in Photosystem II, we set out to synthesise a series of novel photoactive assemblies whereby the components comprising the arrays are linked by a variety of methods. We also considered the capabilities of the electron donors and acceptors separately with focus on porphyrins and quinones respectively. Along this theme, we prepared a number of novel amine derivatives of 2,3-dichloro-l,4-naphthoquinone and studied their electrochemistry. Thiol and mixed thiol/amine derivatives of 2,3-Khchloro-l,4-naphthoquinone were also synthesised and studied electrochemically. Synthesis of a bis-porphyrin-terpyridine molecular array was attempted using three methods. The method showing greatest promise is direct coupling of the porphyrins with the terpyridine. Comparison of the luminescence of Meso-5,10,150-tetrakis(4-iodophenyl)porphyrin with its bromo, chloro and hydrogen analogues was carried out in addition to their zinc complexes. As expected, iodine is the strongest quencher, followed by bromine, chlorine and hydrogen. Altering the substituents of the porphyrin has less of an effect on the luminescence when the porphyrin is metallated with zinc(II) than in the free base. A new route to synthesise 4-iodobenzaldehyde is reported starting with 4-iodotoluene. Two novel A4-substituted porphyrins were prepared utilising the Heck reaction. Using the Mannich reaction, we synthesised two novel tetraza macrocycles functionalised with phenol pendant arms and their lanthanide and transition metal complexes. Synthesis of cyclen bearing specific phenol and naphthol groups at all four positions was found to be hindered, possibly by the stability of the cyclen intermediate in addition to the lack of reactivity of these phenol and naphthol groups. Preparation of a novel cyclen-tetraporphyrin array was found to be forbidden for the same reasons. Following the synthesis of 5-iodovanillin, the preparation of the corresponding symmetrical porphyrin was reported which is a candidate for further work in this area.