published_or_final_version / Chemistry / Master / Master of Philosophy

M.Sc. / The increasing number of individuals living with the HIV virus and the extensive use of antimicrobial medicines has resulted in an increase in opportunistic infections such as tuberculosis, pneumonia, fungal, and viral diseases. In addiction, the drugs currently in use have short comings such as limited efficacy, cell membrane penetration and side effects. The increasing number of opportunistic infections such as systemic fungal infections and the development of resistance to commonly used drugs have prompted the search for answers by producing new and novel ones. Dithiocarbamates (DTCs) have been a subject of major research in the past decade and a number of these compounds have been prepared. Dithiocarbamates are versatile 1,1-dithiolato ligands with broad pharmacological properties. Coordinating these ligands with metals such as copper and nickel may produce compounds with enhanced biological properties and this can be a basis for novel compounds. On the other hand, triphenylphosphine (PPh3) is a good binding ligand for transition metals. Further functionalization of the DTC metal complexes with triphenylphosphine should produce compounds with potential pharmaceutical applications. In this study, several bioactive starting compounds such as indole, imidazole, cyclopentylamine and cyclohexylamine were used to synthesize DTC ligands and their metal complexes of Ni, Co, Cu and Zn. The ligands were obtained in good yields of 55-87% with the complexes in yields of 35-66%. Triphenylphosphine adducts of the DTC metal complexes were also prepared and the yields obtained were between 35-71%. All the prepared complexes and ligands were characterized by Infrared, UV-Vis spectroscopy and NMR (1H, 13C and 31P) spectroscopy.

Luminescent transition metal complexes have arisen as viable alternatives to organic dyes for sensory applications due to their notable advantages. This thesis aimed to synthesize different kinds of iridium(III) complexes as chemosensors and G-quadruplex probes for the detection of metal ions, small molecules, proteins and DNA to demonstrate the versatility of iridium(III) complex in luminescence sensing. Iridium(III) complex chemosensors were synthesized and developed for the detection of Cu2+ and cysteine. The iridium(III) complex plays the role of the "signaling unit", which transduces the analyte binding event into an optical (luminescent) signal and the "receptor unit" attached to the metal complex selectively binds the analyte of interest. Meanwhile, a series of iridium(III) complexes incorporating a variety of C^N and N^N donor ligands were synthesized and were shown to exhibit G-quadruplex-selective binding properties via emission titration, fluorescence resonance energy transfer melting and G-quadruplex fluorescent intercalator displacement experiments. These G-quadruplex-selective Ir(III) complexes were utilized as signal transducers to monitor the conformational changes of oligonucleotides in label-free oligonucleotide-based luminescent detection platforms for metal ion (Ag+), small molecules (cocaine), protein (insulin and AGR2) and gene deletion.

Recently, the Parkin group has synthesized tris[(1-isopropylbenzimidazol-2-yl)dimethylsilyl]methane, [Tismᴾʳⁱᴮᵉⁿᶻ]H, a bulky tetradentate tripodal ligand, which upon deprotonation can coordinate to metal centers via three nitrogen donor atoms and a carbon bridgehead to form metal atrane compounds. The [Tismᴾʳⁱᴮᵉⁿᶻ] ligand has been previously shown to stabilize metal hydride complexes, for example [Tismᴾʳⁱᴮᵉⁿᶻ]MgH [Tismᴾʳⁱᴮᵉⁿᶻ]ZnH. However, no attempts had been previously made to employ this ligand to stabilize heavier Group 12 analogues of these complexes, namely the cadmium and mercury hydride derivatives. In addition, all [Tismᴾʳⁱᴮᵉⁿᶻ] complexes previously reported have employed metals in the first or second oxidation states. In this work, an investigation is undertaken to use the [Tismᴾʳⁱᴮᵉⁿᶻ] ligand to stabilize rare examples of cadmium and mercury hydrides, as well as survey how this ligand binds to Group 13 and transition metals in a variety of oxidation states. In Chapter 1, a series of [Tismᴾʳⁱᴮᵉⁿᶻ] cadmium complexes are reported, including the novel cadmium hydride species [Tismᴾʳᴮᵉⁿᶻ]CdH, which is only the third terminal cadmium hydride species to be structurally characterized by X-ray diffraction. The reactivity of this complex has been probed, revealing the first detailed report of reactivity for a Cd-H bond, as well as the first comparison in relative reactivity between an analogous Cd-H and Zn-H bond. This reactivity of [Tismᴾʳⁱᴮᵉⁿᶻ]CdH includes the ability to insert CO₂ and CS₂, and the resulting cadmium formate and dithioformate complexes have been characterized and discussed, with the latter being the first structurally characterized example of a cadmium dithioformate complex. In addition, [Tismᴾʳⁱᴮᵉⁿᶻ]CdH can undergo hydride extraction to yield the ion pair {[Tismᴾʳⁱᴮᵉⁿᶻ]Cd}[HB(C6F5)₃], a rare example of trigonal monopyramidal cadmium complex. Finally, [Tismᴾʳⁱᴮᵉⁿᶻ]CdMe was synthesized, revealing a different coordination mode of the [Tismᴾʳⁱᴮᵉⁿᶻ] ligand than in the analogous [Tismᴾʳⁱᴮᵉⁿᶻ]ZnMe. In Chapter 2, a series of [Tismᴾʳⁱᴮᵉⁿᶻ] mercury complexes are reported and compared with their cadmium analogues. This comparison revealed several notable differences between [Tismᴾʳⁱᴮᵉⁿᶻ] mercury and cadmium complexes, most notably that the M-O-Si bond angle in [Tismᴾʳⁱᴮᵉⁿᶻ]HgOSiPh₃ is bent, as opposed to the linear [Tismᴾʳⁱᴮᵉⁿᶻ]CdOPh₃ derivative. The synthesis and characterization of [Tismᴾʳⁱᴮᵉⁿᶻ]HgH, the first mercury hydride complex to be structurally characterized by X-ray diffraction, is also reported. This complex has been crystallized in both the κ⁴ and κ³-coordination mode of the [Tismᴾʳⁱᴮᵉⁿᶻ] ligand, representing the first example of a [Tismᴾʳⁱᴮᵉⁿᶻ] compound to be structurally characterized in two coordination modes. In Chapter 3, the synthesis of Group 13 and transition metal [Tismᴾʳⁱᴮᵉⁿᶻ] complexes are reported. These compounds include the first examples of [Tismᴾʳⁱᴮᵉⁿᶻ]M(III) complexes, which reveal that trivalent Group 13 [Tismᴾʳⁱᴮᵉⁿᶻ]M halide compounds form charged ion pairs, whereas trivalent transition metal chloride compounds form six-coordinate octahedral complexes. The investigation into Group 13 [Tismᴾʳᴮᵉⁿᶻ] complexes also led to the structural characterization of [Tismᴾʳⁱᴮᵉⁿᶻ]In→InI₃, the first example of a [Tismᴾʳⁱᴮᵉⁿᶻ] compound with a metal-metal bond. A series of [Tismᴾʳⁱᴮᵉⁿᶻ]MCl (M = Mn, Fe, Co, Cu) complexes are reported and their metrical data compared, along with an investigation into the reactivity of [Tismᴾʳⁱᴮᵉⁿᶻ]NiBr, which led to spectroscopic evidence for a [Tismᴾʳⁱᴮᵉⁿᶻ]NiH complex. Finally, the gold complex [κ1-Tismᴾʳⁱᴮᵉⁿᶻ]AuPPh₃ is reported, which adopts a novel κ1-coordination of the [Tismᴾʳⁱᴮᵉⁿᶻ] ligand.

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy