published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Chemistry / Master / Master of Philosophy

A series of water-soluble platinum(II) terpyridine complexes with functionalized alkynyl ligands and a boronic acid-containing polymer, PAAPBA, have been synthesized and characterized. The photophysical and electrochemical properties of all the platinum(II) complexes have been studied. Some of the complexes have been demonstrated to show ground-state aggregation in organic solvents and aqueous solutions at high concentrations, leading to Pt…Pt and/or π–π interactions and hence the emergence of metal-metal-to-ligand charge transfer (MMLCT) transitions in both the UV−visible and emission spectra. The induced self-assembly of [Pt(tpy)(C≡CC6H4−CH2NMe3-4)](OTf)2 by PAAPBA has been explored for the development of glucose sensing protocols and α-glucosidase assay by monitoring the triplet metal-metal-to-ligand charge transfer (3MMLCT) emission in the near-infrared (NIR) region. [Pt(tpy){C≡CC6H4− {NHC(=NH2+)(NH2)}-4}](OTf)2 has been observed to undergo induced aggregation in the presence of citrate, with good selectivity over other mono- and dicarboxylates in the tricarboxylic acid (TCA) cycle. Enzymatic activity of citrate lyase has also been probed by the emission spectral changes of the complex in the NIR region. A series of water-soluble alkynylplatinum(II) terpyridine complexes and water-soluble conjugated polyelectrolytes (CPEs) have been synthesized and characterized. The UV–vis absorption and emission properties of the platinum(II) complexes and CPEs have been investigated in organic solvents and/or aqueous buffer solutions. The electrochemical properties and ground-state aggregation at high concentrations of the platinum(II) complexes have also been examined. Two-component ensembles containing selected platinum(II) complexes and PPE-SO3− have been studied, and Förster resonance energy transfer (FRET) has been demonstrated from the PPE-SO3− donor to the aggregated complexes as acceptors. The ensemble containing PPE-SO3− and [Pt(tpy)(C≡CC6H4CH2NMe3-4)](OTf)2 has been employed for a “proof-of-principle” label-free detection of human serum albumin (HSA) in pH 3 buffer solutions with high selectivity and sensitivity, while another ensemble containing PPE-SO3− and [Pt{tpy(C6H4CH2NMe3-4)-4’}(C≡CC6H5)](OTf)2 has been utilized for selective label-free detection of G-quadruplex structure of the human telomeric DNA in physiological buffer solutions. A series of water-soluble platinum(II) terpyridine complexes with stimuli-responsive alkynyl ligands and a series of water-soluble platinum(II) metallosupramolecular triblock copolymers have been synthesized and characterized. The photophysical and electrochemical properties as well as the ground-state aggregation of the complexes have been investigated. Some of them have been found to show different electronic absorption and emission properties in aqueous solution at different pHs due to aggregation/deaggregation of the complexes. One of the complexes has been employed for live-cell imaging experiments to locate acidic organelles, such as lysosomes, in MDCK cells. The water-soluble platinum(II) metallosupramolecular triblock copolymers have been found to show an increase in 3MMLCT emission intensity in the red-NIR region with temperature, which has been attributed to the formation of spherical polymeric micelles. The platinum(II) triblock copolymer with pH-responsive –CH2NMe2 moieties has been demonstrated as a NIR-emitting dual sensor for pH and temperature through the changes in hydrophilicity and hence the emission properties with pH and temperature simultaneously. / published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

A number of cationic water-soluble alkynylplatinum(II) terpyridine complexes, [Pt(tpy){C≡CCH2OC6H3-(CH2OH)2-3,5}]OTf, [Pt(tBu3tpy){C≡CCH2OC6H3- (CH2OH)2-3,5}]Cl, [Pt(tpy){C≡CCH2OC6H4-(CH2OH)-4}]OTf, [Pt(tpy){C≡CC6H3- (CH2OH)2-3,5}]OTf, [Pt(tpy){C≡CC6H4-(CH2OH)-4}]OTf, [Pt(tpy)(C≡C－C≡CH)]OTf and [Pt(tpy){C≡CC6H4(CH2NMe3)-4}](OTf)2, have been synthesized. Phosphate anion derivatives of polyanionic nature, e.g. adenosine triphosphate and tyrosine-containing phosphopeptide, were employed to investigate the induced supramolecular helical assembly behaviors of several of the water-soluble platinum(II) complexes through the study of their UV-vis absorption, emission and circular dichroism (CD) spectroscopies. The extent of such induced self-aggregation properties has been shown to be dependent on the concentration of substrates and capable of screening their respective structurally similar analogues. Two of the complexes were further explored for their use as label-free detection probes for real-time monitoring of the conversion of these phosphate anion derivatives to their metabolic products catalyzed by several biologically important enzymes. Michaelis-Menten analyses have been performed to determine the kinetic parameters. Supramolecular self-assembly and disassembly behaviors of water-soluble platinum(II) complexes have also been explored for their sensing applications for biomacromolecules with quantitative analyses based on UV-vis, emission and CD spectral titration studies. Making use of the selective binding affinity of aptamers towards their target substrates, the extent of self-assembly of the platinum(II) complexes in the presence of lysozyme and thrombin, which arose from their electrostatic interactions with the negatively charged aptamers, could be modulated for the quantification of these substrates. The potential applicability of this probing strategy in real biological environment has been assessed. Other than that, CD spectroscopic studies revealed the formation of supramolecular helical assembly of the platinum(II) complexes upon electrostatic interaction with heparin. Such helical conformation of the heparin–complex mixture together with the distribution of the negatively charged functionalities on the heparin have endowed the complex with high differentiating power for screening possible interfering analogues. Insulin has also been employed as a template for inducing the self-assembly of the platinum(II) complex. Changes in negative surface charge distribution on insulin, brought about by its conformational changes upon conversion to insulin amyloid under destabilizing conditions, have resulted in different extent of induced self-assembly of the metal complex. Spectral changes of the platinum(II) complex has provided a convenient monitoring of insulin amyloid formation, with kinetic parameters determined. A number of platinum(II) complexes with nucleobase-functionalized alkynyl ligands, [Pt(tpy)(C≡CCH2-T-1)]OTf, [Pt(tBu3tpy)(C≡CCH2T-1)]OTf, [Pt(tpy)(C≡C– CH2-A-9)]OTf, [Pt(tpy)(C≡CCH2-C-1)]OTf and [Pt(tpy)(C≡CCH2-G-9)]OTf (T = thymine; A = adenine; C = cytosine; and G = guanine), and amide-functionalized terpyridine ligands, [Pt{tpy–(CONHPh)2}(C≡CPh)]PF6 and [Pt{tpy–(CONHC6H13)2} (C≡CPh)]PF6, have been synthesized. Cation-binding properties of [Pt(tpy)(C≡CCH2-T-1)]OTf have been examined using UV-vis and emission spectroscopies, and ESI-MS. Pronounced selectivity towards Hg2+ ions was obtained due to the formation of thymine–Hg2+–thymine base pair, through which the Pt… Pt interactions were turned on. Such binding mechanism has been confirmed with the use of a control complex [Pt(tBu3tpy)(C≡CCH2T-1)]OTf and resonance light-scattering experiments. Anion-binding properties of the complexes with amide-functionalized terpyridine moieties towards spherical and non-spherical anions have been examined with UV-vis and emission spectral titration studies. Drastic color changes were observed for [Pt{tpy–(CONHC6H13)2} (C≡CPh)]PF6 in acetone upon F– ion addition, which was attributed to the F– ion-induced deprotonation of the amide functionalities. / published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Chemistry / Master / Master of Philosophy