Chapter One serves as an introduction to the photophysical properties of square-planar 2,2':6',2/1-terpyridyl and 6-phenyl-2,2'-bipyridylligand complexes of platinum(II). A brief description is provided of the absorption and emission spectra of each complex, the latter generally both in solution and the solid state. The assignments made to the absorption and emission bands are reported, together with the lifetimes ofthe emitting states where these have been measured. The relationship between the molecular and/or crystal structure of the complex and its photophysical properties is discussed. Given this background, the overall aims of the work in this dissertation are presented. In Chapter Two the synthesis and characterisation of nine novelligands are described. These are 4'-(O-naphthyl)-2,2':6',2/1-terpyridine (4'-fJNp-terpy), 4'-(meta-biphenyl)-2,2':6',2/1-terpyridine (4'-mBiph-terpy), 4'-(para-biphenyl)-2,2':6',2"-terpyridine (4'-pBiph-terpy), 4-(fJnaphthyl)- 6-pheny1-2,2'-bipyridine (H4-fJNp-phbipy), 4-(para-biphenyl)-6-pheny1-2,2'bipyridine (H4-pBiph-phbipy), 4-phenyl-6-(2'-pyrazinyl)-2,2'-bipyridine (4-Ph-pzbipy), 4(ortho-CH3-phenyl)-6-(2'-pyrazinyl)-2,2'-bipyridine (4-oMePh-pzbipy), 4-(ortho-CF3-phenyl)6-pyrazinyl-2,2'-bipyridine (4-oCF3Ph-pzbipy) and 4-phenyl-2,6-bis(2'-pyrazinyl)-pyridine (4-Ph-pybipz). In Chapter Three the synthesis, characterisation and photophysical properties of platinum(II) complexes ofthe ligands 4'-jlNp-terpy, 4'-mBiph-terpy and 4'-pBiph-terpy are described. The complexes are salts prepared of the following composition: [Pt(4'-jlNp-terpy)CI]SbF6 (1), [Pt(4'-jlNp-terpy)Cl]BF4 (~), [Pt(4'-jlNp-terpy)Cl]CF3S03 (J), [Pt(4'-mBiph-terpy)Cl]SbF6 (1), [Pt(4'-mBiph-terpy)Cl]BF4 (~), [Pt(4'-mBiph-terpy)Cl]CF3S03(~), [Pt(4'-pBiph-terpy)CI]SbF6 (1), [Pt(4'-pBiph-terpy)Cl]BF4 (~) and [Pt(4'-pBiph-terpy)Cl]CF3S03 (2). Each ligand is characterised by a substituent in the 4'-position that has been designed to permit free rotation of that substituent about the interannular bond to the terpyridyl fragment. The rotational freedom allows the 4'-substituent to adopt an orientation nearly coplanar with that of the terpyridyl fragment. As a result ofthe extensive n-conjugation, there is a strong ligand-centred influence in their excited state emission spectra. Evidence is also presented for 3MLCT (metal 111 to ligand charge transfer) character in the emitting state, in particular that the emission is quenched in coordinating solvents. In addition, an 3ILCT (intraligand charge transfer) contribution has been proposed to account for the exceptionally long lifetimes measured in fluid solution for [Pt(4'-j3Np-terpy)C!t (12 jJs), [Pt(4'-pBiph-terpy)Cq+ (4 jJs) and [Pt(4'-aNpterpy) C!t (17 jJs). We conclude that large easily ionisable substituents in the 4'-position of the terpyridyl moiety ensure long lifetimes in fluid solution for platinum(II) complexes of these ligands. The same assignments apply to the solid state spectra of the yellow or pale orange salts that exhibit monomeric emission in the solid state, these being: [Pt(4'-j3Np-terpy)CI]SbFu (l), [Pt(4'-j3Np-terpy)CI]BF4 (I), [Pt(4'-j3Np-terpy)CI]CF3S03(J.), [Pt(4'-pBiph-terpy)CI]SbFu (1) and [Pt(4'-pBiph-terpy)CI]BF4 (~). In the solid state two additional types of solid state emission have been identified in cases where intermolecular interactions are present. The first type is typical of red or dark orange salts viz., [Pt(4'-mBiph-terpy)Cl]SbFu(1), [Pt(4'-pBiphterpy) Cl]BF4 (red form) (~) and [Pt(4'-pBiph-terpy)Cl]CF3S03 (.2). All three salts exhibit MMLCT (metal-metal to ligand charge transfer) emission brought about by close intermolecular Pt···Pt interactions in the solid. Finally, the three orange compounds [Pt(4'mBiph-terpy)Cl]SbFu.CH3CN (4a), [Pt(4'-mBiph-terpy)Cl]BF4 (~) and [Pt(4'-pBiphterpy) Cl]CF3S03(.2) exhibit simultaneous emission from IL (intraligand) and MMLCT states that are similar in energy. In the case of [Pt(4'-mBiph-terpy)Cl]SbF6.CH3CN (4a) the assigmnent ofMMLCT emission is supported by a X-ray crystal structure determination that shows the cations interacting in dimeric pairs which have a platinum-platinum separation of 3.356(2) A. In Chapter Four the synthesis, characterisation and photophysical properties of the neutral complexes [Pt(4-j3Np-phbipy)Cl] (10) and [Pt(4-pBiph-phbipy)Cl] (11) are described. The ligands, 4-j3Np-phbipy and 4-pBiph-phbipy are closely related to 4'-j3Np-terpy and 4'-pBiphterpy, the only difference being that the terpyridyl fragment is replaced by a phenyl-bipyridyl moiety that binds to the platinum via a deprotonated carbon atom in the ortho-position of the phenyl ring. The stronger a-donor strength of the anionic carbon atom is shown to result in: (i) a marked shift to the red in the MLCT absorption bands for the two complexes and (ii) a significant lowering of the energy ofthe emitting state, as compared to that observed for the cationic terpyridylligand derivatives. The assignment of the emission as 3ILPMLCTin origin remains the same, however, both in solution and in the solid state. In Chapter Five we report the synthesis, characterisation and photophysical properties of a series of platinum(II) complexes of the ligands 4-Ph-pzbipy, 4-oMePh-pzbipy, 4-oCFJPhpzbipy and 4-Ph-pybipz viz., [Pt(4-Ph-pzbipy)CI]BF4 (12), [Pt(4-oMePh-pzbipy)CI]SbF6 (14), [Pt(4-oMePh-pzbipy)CI]BF4 (15), [Pt(4-oMePh-pzbipy)CI]CFJSOJ (16), [Pt(4-oCFJPhpzbipy) CI]SbF6 (17), [Pt(4-oCFJPh-pzbipy)CI]BF4 (18) and [Pt(4-oCFJPh-pzbipy)CI]CFJSOJ (19). These ligands coordinate to platinum via a binding domain analogous to the terpyridyl fragment except that one (or both in the case of 4-Ph-pybipz) of the outer pyridine rings is replaced with a pyrazine ring. The ligands 4-oMePh-pzbipy and 4-oCFJPh-pzbipy are distinguished from 4-Ph-pzbipy by the presence of bulky methyl and trifluoromethyl substituents, respectively, in the ortho position of the peripheral phenyl ring. Monomer emission measured in room temperature fluid solution in a 77 K rigid glass for the three luminophores viz. [Pt(4-Ph-pzbipy)CIt, [Pt(4-oMePh-pzbipy)CIt and [Pt(4-oCFJPhpzbipy) Clr derives from an excited state of JILPMLCT mixed orbital parentage. Their emission energies are stabilised compared to their terpyridyl analogues but emission lifetimes are essentially the same. Solid state emission spectra have been recorded for salts ofthe [Pt(4oMePh- pzbipy)CW and [Pt(4-oCFJPh-pzbipy)CW cations. In every case emission is derived from an excited state brought about by intermolecular interactions, either in the form of excimeric or of MMLCT emission. In general orange compounds ([Pt(4-oCFJPhpzbipy) CI]SbF6 (orangeform ) (17) and [Pt(4-oCFJPh-pzbipy)CI]BF4 (18)} displayexcimeric emission and dark red compounds {[Pt(4-oMePh-pzbipy)CI]SbF6 (14), [Pt(4-oMePhpzbipy) CI]BF4 (15), [Pt(4-oMePh-pzbipy)CI]CFJSOJ(16), [Pt(4-oCFJPh-pzbipy)CI]SbF6 (red form) (17) and [Pt(4-oCFJPh-pzbipy)CI]CFJSOJ (19)} display emission from a MMLCT excited state. The [Pt(4-oCFJPh-pzbipy)CI]SbF6 (17) salt displays polymorphism, existing in two formS, one red and the other orange. In all cases the lower energy of the n-acceptor orbitals of the pyrazinyl-bipyridyl moiety causes emission to be at lower energies compared to that recorded for closely related terpyridyl analogues. Finally, attempts to coordinate the bis-pyrazinylligand, 4-Ph-pybipz, to platinum to form [Pt(4-Ph-pybipz)CI]SbF6 (13) were unsuccessful. / Thesis (PhD.)-University of Natal, Pietermaritzburg, 2002. / National Research Foundation. De Beers Industrial Diamond Division.

The principal goal of this work was to synthesise and fully characterise a range of platinum group metal chelates of bis(pyridine-imine) ligands. These four-nitrogen donor Schiff base ligands are underdeveloped relative to their salen (ONNO donor) counterparts. The purified metal complexes were to be tested for their cytotoxicity against cancer cell lines and their mode of interaction (expected to be intercalation) studied. The syntheses, spectroscopic and structural properties of some novel and some already known bis(pyridine-imine) ligands are described. Furthermore, UV-Vis, IR and NMR spectroscopy, as well as electrospray ionisation mass spectrometry, have been used to characterize the ligands and comparisons were made with relevant literature. Fifteen Schiff base ligands were successfully condensed from a 2-formyl or 2-ketopyridine starting material and a diamine bridging group, while the attempted syntheses of a further three are described. Literature methods or variations thereof were employed in the syntheses of these derivatives, which generally resulted in good yields. X-ray quality crystals were obtained and X-ray structures were determined for four novel ligands and five unexpected cyclised hexahydropyrimidine- and imidazole-containing bidentate ligands, of which three were novel structures. The series of bicationic palladium and platinum complexes synthesised here were analysed by NMR, IR and UV-Vis techniques, as well as X-ray crystallography when possible. The complexes were prepared by reacting the free ligands with platinum group metal salts in refluxing acetonitrile. The complexes exhibit infrared bands for the imine C=N stretch between 1604–1670 cm-1; around 15–40 cm-1 lower than the free ligands. The 1H NMR spectra in the CH=N chemical shift region also display shifts (0.1 to 0.8 ppm for the palladium complexes or 0.4 to 0.9 ppm for the platinum complexes) which are consistent with metallation. X-ray crystal structures were obtained for eight novel metal complexes, which all crystallised in the monoclinic crystal system. The solid state analysis shows changes in the free ligands upon introduction of the metal ions, caused by the coordination process. Metallation of the free ligands led to twisting of the ligands due to size effects and the spatial restrictions of the coordination geometry of the central metal ions. The structures were generally solved by direct methods and refined to R1 = 0.0729 or less. Singlecrystal X-ray diffraction analysis confirmed that the mononuclear complexes exhibit a distorted square planar coordination sphere composed of the four donor nitrogen atoms (two imine and two pyridyl nitrogen atoms) from the Schiff base ligands. The complexes were generally very stable and differed by the type of metal ion (platinum(II) or palladium(II)) and the diamine bridging group (2-carbon or 3-carbon linking chain with various substituted groups). A range of unconventional F···H−C contacts is revealed to play an important role in the overall bonding and crystal packing of many complexes. To better understand our measured data and to separate the intrinsic properties of our molecules from intermolecular interactions, theoretical calculations at the DFT (B3LYP) level were carried out. These calculations predict the structural and spectroscopic properties for the free ligands and their metallated counterparts. DFT simulations were performed for the fifteen synthesised ligands (B3LYP functional, 6-31G** basis set), as well as three projected ligands that could not be synthesised, and for all proposed thirtysix metal complexes (B3LYP functional, SDD basis set). DFT simulations were used to obtain theoretical IR frequency data which was compared to the literature and used to prove the location of a local minimum energy structure in the geometry optimisation rather than a transition state. Our results collectively showed the B3LYP level of theory to be useful in the prediction of IR frequencies for these Schiff base ligands as well as the platinum(II) and palladium(II) complexes. Geometry optimisations performed using density functional theory for the free ligands and metal complexes were compared, where possible, with X-ray data. For the free ligands the main structural differences were observed for the position of the pyridyl-imine "arms" of the ligands with relatively good agreement between the two structures for the bridging groups. On the other hand, the metal complexes showed greater discrepancies for the bridging groups rather than for the pyridine rings. These differences were also affected by the length of the carbon bridge; the longer the carbon bridge, the less variation was observed. The trends in the variation of bond distances and angles with the metal ion identity and ligand structure delineated by DFT simulations were matched by similar trends in the X-ray data. Differences between the gas phase calculated geometries and those determined by Xray diffraction were attributed to packing effects in the solid state and intermolecular interactions not being accounted for during DFT computations. The impressive similarity observed between the structures obtained from X-ray crystallography and computed by DFT shows the applicability of these computations at the B3LYP level of theory. They were able to accurately predict structural and spectroscopic properties for the ligands and complexes presented in this work. The in vitro cytotoxicities of some of the metal complexes were evaluated against two mouse cancer cell lines. The compounds tested had lower than expected cytotoxicity towards the cell lines studied with IC50 values > 100 μM. The interaction of the complexes with calf thymus DNA has been explored by using absorption studies. From the observed changes in absorption possible modes of binding to DNA have been proposed for the metal complexes. Significant changes were observed in the absorption spectra upon interaction of the complexes with DNA, from which large binding constants were determined. The changes were, however, not as intense as expected nor were the spectral variations typical of intercalating drugs. There were also no bathochromic shifts nor any isobestic points observed for most of the metal complexes, except one. For the cationic PGM chelates studied, the lack of shift in the wavelength of the visible range MLCT band maximum and small changes in the band intensity were more indicative of weak electrostatic interactions. Our spectral data were thus interpreted as being consistent with non-intercalative binding; either simple electrostatic adduct formation or major/minor groove binding. The binding constant values (Kb) of the metal complexes estimated from the titration with calf thymus DNA monitored by absorption spectroscopy were all in the range of 105 M-1. This is within the range of those reported for other platinum(II) and palladium(II) metal complexes that have shown intercalation and/or groove binding. With the lack of inhibition of growth of the selected cancer cell lines it is possible that the compounds do not reach nuclear DNA in living cells or that such compounds are possibly substrates for efflux transporters. All the metal complexes in this work were determined to not be pure DNA intercalators as had been expected; however, in some cases partial intercalation cannot be ruled out from the spectral data. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.

Thesis (Ph. D.)--University of Hong Kong, 2009. / Includes bibliographical references (leaves 275-300) Also available in print.

Thesis (Ph.D.)--University of Western Australia, 2006.

Thesis (Ph. D.)--University of Hong Kong, 2008. / Also available online.

Thesis (Ph. D.)--University of Hong Kong, 2008. / Also available in print.

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Hong Kong, 2010. / Includes bibliographical references (leaves 258-281). Also available online.

Thesis (M. Phil.)--University of Hong Kong, 1999. / Includes bibliographical references (leaves 170-183).

Thesis (Ph. D.)--University of Hong Kong, 2009. / Includes bibliographical references (leaves 252-253). Also available in print.