Europium and terbium complexes of a series of ter- and quarterpyridine-N-oxide ligands have been prepared and structurally characterised by crystallographic studies. The solid-state structures reveal some interesting topologies of the ligands due to the flexibility introduced to the coordination sphere by the N-oxide donors. Europium and terbium complexes were also prepared for a series of quinquepyridine-N-oxides Luminescence studies of the N-oxide complexes in acetonitrile show typical europium and terbium emission spectra, dominated by the 5D07F2 and 5D7F5 transitions respectively. No simple trend was revealed in the relative quantum yields, with [Eu(4-bisphenyl-quarterpyridine-1-quarteroxide)2][ClO4]3 having the most intense luminescence. Decomplexation of the non-oxidised ligand complexes was observed at low solution concentrations in the luminescence spectra and so strong lanthanide-binding groups were introduced to the 6 positions of the external pyridine rings of the ter-, quarter- and quinquepyridine ligands to improve complex stability. Lanthanide-binding groups introduced were hard, anionic carboxylate groups and also, the more organic solvent soluble,tert-butyl amide groups. Europium and terbium complexes of the series of ter-, quarter- and quinquepyridine carboxylic acid andtert-butyl amide ligands were prepared and the ligands shown to be capable of sensitising the trivalent lanthanide europium and terbium ions. Luminescence studies revealed an increased binding strength of the ter-, quarter- and quinquepyridine carboxylic acid ligands with no decomplexation at low solution concentrations being observed. From the relative quantum yields [Eu(4-phenyl-2,2-terpyridine- 6,6-diarboxylic acid)(H2O)2][ClO4]2 was determined to have the most intense luminescence. Also, a trend of the carboxylic acid ligands being more suitable for Eu(III) sensitisation and thetert-butyl ligands being more suitable for Tb(III) sensitisation was revealed.

Finally, a series of novel cyanobipyridine-derived zinc(II) bis(thiolate) complexes were prepared excellently by a microwave-assisted cross-coupling/complexation sequence and display luminescence that can be modulated using intrinsic functionality and ancillary ligands.

No description available.

A series of new azaxanthone chromophores has been established as sensitisers of europium and terbium emission in aerated aqueous media. Chromophores incorporating either a pyridyl or pyrazoyi moiety have been devised with large molar extinction coefficients and long excitation wavelengths. The pyridyl and pyrazoyi-1-azaxanthones have been incorporated into an array of functionalised macrocycles, to yield a series of emissive europium and terbium complexes, including examples suitable for conjugation. The complexes possess high emissive quantum yields (Φ (_Eu) = 25 %, Φ (_Tb) = 64 %) and long emissive lifetimes (up to 2.3 ms for Tb) in aqueous media. These properties arise from exclusion of coordinated water molecules, as a result of bidentate chelation of the heterocyclic chromophores. Quenching studies of the lanthanide excited states indicate that non-covalent protein association shields the complexes from quenching by endogenous electron rich species, such as urate and ascorbate. Under simulated cellular conditions, (0.4 mM serum albumin, 0.13 mM urate) the emissive lifetimes remain within 10 % of that observed in water, indicating protein binding does not quench the lanthanide excited states. Cellular uptake experiments have been performed with CHO and NIH-3T3 cell lines. Examination using fluorescence microscopy reveals cellular uptake, with complexes exhibiting a time-dependent localisation profile partitioning between mitochondrial and lysosomal regions. Following establishment of an efficient and reproducible method of conjugation, complexes have been covalently attached to benzyl guanine vectors to examine their performance as components in homogeneous time resolved fluorescence (HTRF) assays.

The first chapter introduces the area of phenyleneethynylenes. The parent of the novel systems presented here, 1,4-bis(phenylethynyl)benzene (BPEB), is an ex- tended π–conjugated system, known for its interesting structural, optical and elec- tronic properties. Derivatives of this system have demonstrated great potential in the field of organic electronics, particularly as components in OLEDs, PV cells and molecular wires. An introduction to the phenyeneethynylenes and fundamentals of various photophysical properties is presented, along with a brief overview of several synthetic methodologies available for the preparation of arylethynylenes. In Chap- ter 2 the equipment and methods used for the determination of the excited state properties of the compounds are discussed. The preparations and excited state study of a series of thiophene–based aryle- neethynylene oligomers are reported in Chapter 3. This chapter begins with a short review of thiophene based molecules followed by a discussion of the synthetic pro- cedures available for the preparation of the various dibromoheteroarene cores. The work presented here has allowed comparisons to be drawn with the photophysical and structural properties of the known 2,5-bis(phenylethynyl)thiophene, upon mod- ification of the central thiophene core. Oligomers containing an oxidised thiophene (thiophene-1,1-dioxide) displayed significantly red–shifted absorption and emission bands compared to those of the parent and derivatives, indicating significant ICT in the excited state. Furthermore, the lifetimes of the thiophene-1,1-dioxide sys- tems were significantly longer than those of the non–oxidised derivatives, resulting in much higher rates of fluorescence decay (kf ). Quantum yields for this series of thienyl arylethynylenes varied from 3 % to 43 %. Several systems featuring pe- ripheral substituents (OMe and CN) were prepared to probe the effect of electron donating and withdrawing groups on the photophysical properties of the oligomers. Also, two of the oligomers prepared featured a break in the conjugation across the thiophene derivative and one of these molecules exhibited phosphorescence upon cooling to 77 K, allowing direct measurement of the triplet energy. Chapter 4 begins with a short review of the diazole heterocycles, to illustrate the potential applications of these systems. The novel oxygen-containing diazoles were compared to their sulfur–containing analogues, which have been reported pre- viously in the literature. The benzofurazan and benzothiadiazole–based oligomers have been appended with peripheral substituents in the form of electron–donating and electron–withdrawing groups (R = H, t–Bu, OMe, NH2, CO2Me and CN), in an attempt to monitor the effect of increasing electron donation and electron withdrawing effects on these already electron–deficient oligomeric systems. 2,5- bis(Phenylethynyl)-1,3,4-oxadiazole exhibited high energy absorption and emission maxima, as well as relatively narrow absorption and emission profiles, in contrast to the broad profiles of the other electron–deficient systems. The benzofurazan se- ries exhibited broad, unstructured emission profiles, yet all systems displayed two distinct absorption bands. Fluorescence quantum yields of these compounds were generally very high; for 4,7-bis(4-t-butylphenylethynyl)benzofurazan, φf = 0.96. All benzofurazan and benzothiadiazole arylethynylenes displayed fluorescence lifetimes of several nanoseconds. Chapter 5 presents a comparison of the photophysical properties of selected molecules from Chapters 3 & 4 and BPEB, as well as suggestions for future work. All novel systems have been purified and characterised using typical methods (1H and 13C NMR spectroscopy, accurate mass spectrometry, melting point, and elemen- tal analysis and crystallographic structure determination where possible) and their excited state properties have been probed using photophysical methods (including room and low temperature UV–vis absorption and fluorescence spectroscopy and fluoresence quantum yields and lifetime). Ab initio calculations have afforded opti- mised geometries which have been compared to molecular structures determined us- ing X–ray diffraction and vibrational spectroscopy. TD–DFT calculations have been used to rationalise the observed photophysical spectra, helping with assignment of bands in the fluorescence spectra, aiding the determination of states responsible for absorption and emission.

The literature dealing with the primary processes in the photolysis of acetone with ultra-violet light has been reviewed and the important areas where reliable data exists have been identified. Gaps in the knowledge necessary for a complete description of the process have also been noted and measurements have been made which made possible a much fuller description of the primary process. An apparatus has been constructed which measures the light emission from the excited states formed by electronically excited acetone and the effect of temperature, acetone pressure, oxygen, iodine and Xenon on the excited states has been measured. Quantum yields of methyl iodide from the photolysis of acetone at 3130A have been measured by a technique devised specially for this work and by combining these results with the light emission work an over-all mechanism has been produced which embraces both sets of data. The role of the triplet excited state has been shown to be more important than was postulated before this work commenced, and the results obtained indicate that the mechanism of the primary process must be more complex than previous workers had supposed.

The design of responsive optical cellular probes remains a key challenge for biology and medicine. Luminescent lanthanide complexes are well suited for this purpose, with their information-rich emission profiles, and long luminescence lifetimes which allow gating out of interfering background signals. In order to design complexes for in cellulo applications, it is important to gain a greater understanding of the cellular behaviour of such complexes. This thesis describes work performed to this end. The studies described herein utilise a broad range of complexes synthesised in Durham. These complexes comprise a Eu(^3+) or Tb(^3+) ion encapsulated in a cyclen macrocycle to which is attached a sensitising chromophore and two or three amide- or carboxylate-based pendant arms. The synthesis and characterisation of one set of such complexes is described. Modification of the pendant arm was shown to result in considerable variation of the complex helicity and structure, but with no alteration in the cellular behaviour. This thesis also describes work which was performed to explore various aspects of cellular behaviour. The range of observed sub-cellular localisations are described, structure-localisation relationships presented and the observation of nucleolar localisation in some cases investigated. Studies of uptake mechanisms indicated that all complexes are transported across the cell membrane by a common pathway of macropinocytosis. Examples of various sub-cellular speciation states are presented, with detailed investigation of one case of reversible protein binding which induces a helicity change in the complex in an enantioselective fashion. Finally, the effect of the complexes on the cellular homeostasis is discussed, with the finding that complexes do not generally perturb the normal function of the cell. This work therefore demonstrates that most luminescent lanthanide complexes do exhibit behaviour which makes them suitable for use as cellular probes. They are generally non-toxic, readily internalised and localise to specific organelles, and have demonstrated utility in reporting on the sub-cellular environment.

No description available.

No description available.

No description available.