https://www.um.edu.mt/library/oar/handle/123456789/77289 Mon, 13 Apr 2026 03:19:21 GMT 2026-04-13T03:19:21Z https://www.um.edu.mt/library/oar/handle/123456789/78449 Title: Fluorescent molecular logic gates for pH and pE for cell imaging applications Abstract: Novel molecules for sensing pH and redox potential (pE) were designed and synthesised starting from the asymmetrical 1,8-naphltalimide fluorophore. Attachment of a proton receptor and/or electron donor at either the N-imide or 4-position resulted in the molecular engineering of several positional isomers. Three novel pH-pE molecules of various modular designs were synthesised including 'fluorophore-spacer1-receptor-spacer2-electron-donor', 'electron -donor-spacer1-fluorophore-spacer2-receptor', and 'electron-donor1-spacer1-receptor1-spacer2-fluorophore-spacer2-receptor2-spacer4-electron-donor2' prototype. The receptor was either N-methylethylenediamine or piperazine, whilst the electron-donor was forrocene, both of which were connected via methylene or ethylene spacers. In addition, two model fluoroscent pH indicators were designed and studied, based on a 'fluorsphore-spacer-receptor' format, whilst a third fluorescent pH indicator was synthesised with a 'receptor1-spacer1-fluorophore-spacer2-receptor2' modular format. Description: M.SC.CHEMISTRY Sun, 01 Jan 2017 00:00:00 GMT https://www.um.edu.mt/library/oar/handle/123456789/78449 2017-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/78113 Title: Crystal formation of purine salts to investigate seeding processes Abstract: Purines and punne salts are known to be the most widely distributed nitrogen containing compounds found in nature, and have a very important role in metabolism. Most purines form crystals when they precipitate out of solution, some of which deposit in various parts of the body, especially in the joints. The latter is responsible for the medical condition known as gout, which is characterised by inflammation. With this in mind, experiments were designed to explore whether the shape of these crystal that form in the body can be altered. In this study, aqueous solutions of purines and salts of purines were prepared. Crystals that precipitated out of these solutions under different conditions were isolated and observed under the polarised light-microscope. On the whole, theobromine formed small columnar prisms, while xanthine formed small and medium-sized crystals, which appear circular with a Maltese cross pattern at the centre. Caffeine was, by far, the easiest purine to crystallise, owing to its high solubility in an aqueous solution. In general, acicular or needle-like crystals of caffeine were formed, but at very low temperatures, plate-like caffeine crystals were obtained. Guanine and uric acid formed very few crystals owing to them being practically insoluble in water. Crystals of adenine were generally needle-like, comparable to those fonned by caffeine. Additionally, they formed bundles or clusters, with the needles pointing outwards from the clusters. Diversity of crystals involving theobromine increased when adding dicarboxylic acids in the solution. Long and slender plate-like crystals were observed. The introduction of sacchann m solution enabled the crystal morphologies to change drastically. Interesting dendritic crystals were formed from a saccharin-theobromine solution. Change in size and shape of theobromine was also observed on introducing alcohol in the aqueous environment. Caffeine crystals were overall unchanged on the introduction of dicarboxylic acids, saccharin or alcohols. Description: M.SC.CHEMISTRY Sun, 01 Jan 2017 00:00:00 GMT https://www.um.edu.mt/library/oar/handle/123456789/78113 2017-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/77941 Title: Fluorescent molecular logic gates for the early detection of corrosion Abstract: Four novel molecules for sensing pH and redox potential (pE) were designed and synthesised based on the asymmetrical 1,8-naphthalimide fluorophore. Attachment of the proton receptor and electron donor at either the N-imide or 4-position produced two pairs of positional isomers. Two of the molecules are designed based on an 'electron donor-spacen- fluorophore-spacer-recepton' modular format with dimethylamine or morpholine as the proton receptors and ferrocene as the electron donor. The two other molecules consist of the same chemical units, but adopt a 'recepton-spaceri-fluorophore -spacer-electron-donor' arrangement. The ferrocene and proton receptors are connected to the fluorophore via a methylene and ethylene spacers, respectively. Furthennore, a three-input logic gate for Na+, pH and pE was synthesised based on 'electron donor-spacen-fluorophore-spacer-recepton- space-recepton' design. A piperazine unit was employed as recepton for protons and a benzo-15-crown-5 as receptor2 for Na+ separated by a methylene group. Description: M.SC.CHEMISTRY Sun, 01 Jan 2017 00:00:00 GMT https://www.um.edu.mt/library/oar/handle/123456789/77941 2017-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/77875 Title: The interaction of lanthanides and lanthanide-carbene complexes with crown ethers Abstract: The syntheses of novel organometallic compounds, using cyclic and semi-cyclic compounds, were investigated. These included the synthesis of an air-sensitive lanthanide complex, by using a carbene as the ligands. This was achieved by using lanthanum as the metal centre, and a bis(iminophosphorano )methanide as the ligand. The intermediates of this reaction were successfully observed, but the final product was not obtained successfully. The syntheses of several air-stable lanthanide complexes, with the use of different oxygen-based crown ethers, were also carried out. The lanthanides used included lanthanum, europium, gadolinium, and ytterbium. The crown ethers which were used included 18-crown-6, 21-crown-7, and 24-crown-8. The synthesis of lanthanide-crown ether complexes, as high-quality single crystals, was carried out by using standard crystallisation techniques, such as grinding and vapour diffusion, using water-ethanol and water-propanone as solvent pairs. Crystals of a sufficient quality were analysed by means of microscopy, infra-red spectroscopy, hot-stage microscopy, and single crystal X-ray diffraction. A total of 32 unique samples were prepared, and eight of these samples produced adequate crystals for analysis. Single crystal X-ray diffraction was used to collect diffraction data for eight samples, all of which have now been analysed. These samples are not new complexes, but are instead identical to certain lanthanide-crown ether complexes which were previously produced. However, one sample (GG2112) showed intrinsic modulation of the crystal structure at low temperatures, which is not visible at room temperature. Description: M.SC.CHEMISTRY Sun, 01 Jan 2017 00:00:00 GMT https://www.um.edu.mt/library/oar/handle/123456789/77875 2017-01-01T00:00:00Z