title: Studies on the coordination chemistry of functionalised thiourea ligands

authors: Risi, Matthew

abstract: This thesis explores the coordination chemistry of functionalized thiourea ligands with electron-withdrawing sulfonyl, phosphoryl and diacyl substituents. These ligands, despite their structural similarity to acylthioureas, exhibit unique coordination behaviours that have been largely understudied within the literature, particularly with platinum group and related late transition metals. By utilizing a series of characterization techniques, including single-crystal X-ray diffraction, electrospray ionization mass spectrometry, NMR spectroscopy, and computational methods, this work aimed to establish foundational knowledge to inform future application-driven research within this research domain.

Firstly, dianionic sulfonylthiourea ligands were investigated towards platinum(II), revealing a distinct preference for distal isomer (coordinated via S,N-sulfonyl) which was found to be a result of a stabilizing chalcogen bond between thiourea sulfur and sulfonyl oxygen atoms. This non-covalent interaction, confirmed computationally and crystallographically, highlights the potential for modulating isomer selectivity of thiourea ligands through ligand design. Following this study, Chapter 3 extends the investigation of dianionic and monoanionic sulfonylthiourea ligands to organometallic ruthenium(II), iridium(III), and rhodium(III) in the piano stool arrangement. The resulting complexes demonstrated how steric factors influence isomerization and resulting coordination modes. While the proximal isomer persisted among the prepared complexes, using sufficient steric bulk around the metal centre, the distal isomer was formed, exhibiting proximal to distal isomerization in the liquid state. Anticancer assessments against various human cancer cell lines were performed externally which show moderate activity. Trends indicating enhanced efficacy through increased ligand lipophilicity were observed among the ruthenium(II) complexes. In Chapter 4, platinum(II) complexes with dianionic phosphorylthiourea ligands are characterized, revealing a consistent distal isomer preference modulated by bulky substituents. The inclusion of phosphorus atoms onto the ligand enhances characterization capabilities over similar ligands via ³¹P{¹H} NMR spectroscopy, providing a robust tool for elucidating coordination modes. Chapter 5 introduces symmetric diacylated thioureas as versatile ligands for platinum(II), palladium(II), and gold(III). Their coordination mode, forming four-membered S,N coordinated metallocycles, contrasts with the related monoacylated acylthiourea analogues. Moreover, the inclusion of a second acyl group onto the thiourea core allows for additional chalcogen and hydrogen bonding interactions which dominate the structure of the complex. Finally, Chapter 6 presents a ruthenium cymene complex featuring a neutral monodentate diacylthiourea ligand. Non-covalent interaction analysis identifies chalcogen and hydrogen bonding as determining the structural arrangement, reinforcing the importance of these features in future applications. 
Collectively, this thesis provides a comprehensive foundation for understanding the coordination chemistry of functionalized thiourea ligands bearing electronegative substituents, opening avenues for their tailored use in fields ranging from catalysis to medicinal chemistry.

text: Studies on the coordination chemistry of functionalised thiourea ligands This thesis explores the coordination chemistry of functionalized thiourea ligands with electron-withdrawing sulfonyl, phosphoryl and diacyl substituents. These ligands, despite their structural similarity to acylthioureas, exhibit unique coordination behaviours that have been largely understudied within the literature, particularly with platinum group and related late transition metals. By utilizing a series of characterization techniques, including single-crystal X-ray diffraction, electrospray ionization mass spectrometry, NMR spectroscopy, and computational methods, this work aimed to establish foundational knowledge to inform future application-driven research within this research domain.

Firstly, dianionic sulfonylthiourea ligands were investigated towards platinum(II), revealing a distinct preference for distal isomer (coordinated via S,N-sulfonyl) which was found to be a result of a stabilizing chalcogen bond between thiourea sulfur and sulfonyl oxygen atoms. This non-covalent interaction, confirmed computationally and crystallographically, highlights the potential for modulating isomer selectivity of thiourea ligands through ligand design. Following this study, Chapter 3 extends the investigation of dianionic and monoanionic sulfonylthiourea ligands to organometallic ruthenium(II), iridium(III), and rhodium(III) in the piano stool arrangement. The resulting complexes demonstrated how steric factors influence isomerization and resulting coordination modes. While the proximal isomer persisted among the prepared complexes, using sufficient steric bulk around the metal centre, the distal isomer was formed, exhibiting proximal to distal isomerization in the liquid state. Anticancer assessments against various human cancer cell lines were performed externally which show moderate activity. Trends indicating enhanced efficacy through increased ligand lipophilicity were observed among the ruthenium(II) complexes. In Chapter 4, platinum(II) complexes with dianionic phosphorylthiourea ligands are characterized, revealing a consistent distal isomer preference modulated by bulky substituents. The inclusion of phosphorus atoms onto the ligand enhances characterization capabilities over similar ligands via ³¹P{¹H} NMR spectroscopy, providing a robust tool for elucidating coordination modes. Chapter 5 introduces symmetric diacylated thioureas as versatile ligands for platinum(II), palladium(II), and gold(III). Their coordination mode, forming four-membered S,N coordinated metallocycles, contrasts with the related monoacylated acylthiourea analogues. Moreover, the inclusion of a second acyl group onto the thiourea core allows for additional chalcogen and hydrogen bonding interactions which dominate the structure of the complex. Finally, Chapter 6 presents a ruthenium cymene complex featuring a neutral monodentate diacylthiourea ligand. Non-covalent interaction analysis identifies chalcogen and hydrogen bonding as determining the structural arrangement, reinforcing the importance of these features in future applications. 
Collectively, this thesis provides a comprehensive foundation for understanding the coordination chemistry of functionalized thiourea ligands bearing electronegative substituents, opening avenues for their tailored use in fields ranging from catalysis to medicinal chemistry.

year: 2025-01

title: How convergent are regional house prices in the United Kingdom? Some new evidence from panel data unit root testing

authors: Holmes, Mark J.

subjects: panel data unit root

abstract: Using a variety of econometric methods, existing studies have failed to reach a consensus on whether or not UK regional house prices are engaged in kong-run equilibrium relationships with each other. Using data for the 197302005 study period, this study offers a novel approach to this debate through the application of unit root testing within a seemingly unrelated regression framework. It is argued that there exist significant advantages in this approach over and above existing univariate and panel data unit root testing procedures. The results indicate that the majority of UK regions exhibit regional house price convergence. However, there is an east-west split in terms of whether regional house prices have a tendency towards long-run equilibrium relationship with UK prices as whole. This is also evidence of considerable heterogeneity in the regional speeds of adjustment towards long-run equilibrium.

text: How convergent are regional house prices in the United Kingdom? Some new evidence from panel data unit root testing Using a variety of econometric methods, existing studies have failed to reach a consensus on whether or not UK regional house prices are engaged in kong-run equilibrium relationships with each other. Using data for the 197302005 study period, this study offers a novel approach to this debate through the application of unit root testing within a seemingly unrelated regression framework. It is argued that there exist significant advantages in this approach over and above existing univariate and panel data unit root testing procedures. The results indicate that the majority of UK regions exhibit regional house price convergence. However, there is an east-west split in terms of whether regional house prices have a tendency towards long-run equilibrium relationship with UK prices as whole. This is also evidence of considerable heterogeneity in the regional speeds of adjustment towards long-run equilibrium.

year: 2007

title: Mai uta ki tai: Cyclone-driven suspended sediment effects on early benthic juvenile kōura (Jasus edwardsii), Te Ākau o Tokomaru, Aotearoa

authors: Karaha-Paki, Vijuan

abstract: Kōura (Jasus edwardsii) are ecologically, culturally, and economically significant taonga species central to mahinga kai systems throughout Aotearoa New Zealand. In Te Tairāwhiti, particularly Te Ākau o Tokomaru, Cyclone Gabrielle (February 2023) resulted in unprecedented sediment loads being delivered to coastal waters, smothering inshore rocky reefs that serve as critical nursery habitats for settling puerulus and juvenile kōura. This research investigated how repeated suspended sediment exposure affects the body condition, survival, and physiological condition of early benthic juvenile kōura, integrating Western scientific methods with mātauranga Māori perspectives to support kaitiakitanga and ecosystem recovery. 

A 52-day pulse-based laboratory experiment exposed 81 early benthic juvenile kōura to three treatment levels: Control (0 mg/L), Tobserved (1,000 mg/L), and Tmaximised (5,000 mg/L) suspended sediment concentrations, alternating between exposure phases and recovery periods to simulate natural post-storm sedimentation dynamics. Sediment was sourced from the Mangahauini River mouth to reflect local conditions. Kōura were initially housed communally (Days 1-19), and then separated into individual tāruke following observed cannibalism. Across the experiment, body weight to carapace length (BW:CL) ratios, survival, blood refractive index, gill condition, and moult stage were assessed. 

All treatment groups began with statistically equivalent body condition (p = 0.135), but cumulative effects emerged over time. During communal housing, mortality was highest in the Tobserved treatment (51.9%) compared with Control and Tmaximised treatments (both 18.5%). After separation, Tmaximised individuals showed the greatest losses (45.5%), mostly during the recovery rather than exposure phases. Overall mortality reached 45.7%, with sediment-exposed treatments experiencing 55% (Tmaximised) to 59% (Tobserved) losses compared with 22.2% in the Controls (p = 0.001). 

By Day 52, sediment exposure significantly reduced body condition (p = 0.016), with the Controls maintaining higher BW:CL ratios than Tmaximised (p = 0.013). Gill assessments indicated universal and severe damage in sediment-exposed kōura (100%) but none in the Controls (0%). Quantitative image analysis confirmed strong sediment concentration- dependent effects across all damage metrics – particle lodgement, filament integrity, surface discolouration, and composite scores (all p < 0.001) – with structural deformities in 66.7% of Tobserved and 100% of Tmaximised individuals. Blood refractive index showed no treatment differences, and 84.1% of kōura remained in intermoult stage at Day 52, with no significant difference in moult stage distribution between treatments (p = 0.328). However, moult frequency during the individual phase was lower in sediment-exposed groups compared to the Controls (Control: n = 11, Tobserved: n = 4, Tmaximised: n = 5). 

These findings show that suspended sediment exposure poses population-level threats to kōura recruitment through irreversible gill damage and delayed mortality. Elevated cannibalism during communal holding, particularly observed in the Tobserved treatment, likely resulted from temporal clustering of moult events rather than sediment-induced behaviour. For Te Ākau o Tokomaru and the wider CRA 3 fishery, this highlights the need for integrated catchment-to- coast management addressing land-derived sediment inputs and protecting coastal nursery habitats. From a Te Ao Māori perspective, sedimentation represents a disruption to whakapapa relationships with Tangaroa and a weakening of mauri in coastal ecosystems. Restoring these connections requires co-governance frameworks that embed mātauranga Māori, empower kaitiaki-led monitoring and rāhui, and address the cumulative impacts of land-use intensification and repeated cyclone events on ecosystem resilience in Te Tairāwhiti.

text: Mai uta ki tai: Cyclone-driven suspended sediment effects on early benthic juvenile kōura (Jasus edwardsii), Te Ākau o Tokomaru, Aotearoa Kōura (Jasus edwardsii) are ecologically, culturally, and economically significant taonga species central to mahinga kai systems throughout Aotearoa New Zealand. In Te Tairāwhiti, particularly Te Ākau o Tokomaru, Cyclone Gabrielle (February 2023) resulted in unprecedented sediment loads being delivered to coastal waters, smothering inshore rocky reefs that serve as critical nursery habitats for settling puerulus and juvenile kōura. This research investigated how repeated suspended sediment exposure affects the body condition, survival, and physiological condition of early benthic juvenile kōura, integrating Western scientific methods with mātauranga Māori perspectives to support kaitiakitanga and ecosystem recovery. 

A 52-day pulse-based laboratory experiment exposed 81 early benthic juvenile kōura to three treatment levels: Control (0 mg/L), Tobserved (1,000 mg/L), and Tmaximised (5,000 mg/L) suspended sediment concentrations, alternating between exposure phases and recovery periods to simulate natural post-storm sedimentation dynamics. Sediment was sourced from the Mangahauini River mouth to reflect local conditions. Kōura were initially housed communally (Days 1-19), and then separated into individual tāruke following observed cannibalism. Across the experiment, body weight to carapace length (BW:CL) ratios, survival, blood refractive index, gill condition, and moult stage were assessed. 

All treatment groups began with statistically equivalent body condition (p = 0.135), but cumulative effects emerged over time. During communal housing, mortality was highest in the Tobserved treatment (51.9%) compared with Control and Tmaximised treatments (both 18.5%). After separation, Tmaximised individuals showed the greatest losses (45.5%), mostly during the recovery rather than exposure phases. Overall mortality reached 45.7%, with sediment-exposed treatments experiencing 55% (Tmaximised) to 59% (Tobserved) losses compared with 22.2% in the Controls (p = 0.001). 

By Day 52, sediment exposure significantly reduced body condition (p = 0.016), with the Controls maintaining higher BW:CL ratios than Tmaximised (p = 0.013). Gill assessments indicated universal and severe damage in sediment-exposed kōura (100%) but none in the Controls (0%). Quantitative image analysis confirmed strong sediment concentration- dependent effects across all damage metrics – particle lodgement, filament integrity, surface discolouration, and composite scores (all p < 0.001) – with structural deformities in 66.7% of Tobserved and 100% of Tmaximised individuals. Blood refractive index showed no treatment differences, and 84.1% of kōura remained in intermoult stage at Day 52, with no significant difference in moult stage distribution between treatments (p = 0.328). However, moult frequency during the individual phase was lower in sediment-exposed groups compared to the Controls (Control: n = 11, Tobserved: n = 4, Tmaximised: n = 5). 

These findings show that suspended sediment exposure poses population-level threats to kōura recruitment through irreversible gill damage and delayed mortality. Elevated cannibalism during communal holding, particularly observed in the Tobserved treatment, likely resulted from temporal clustering of moult events rather than sediment-induced behaviour. For Te Ākau o Tokomaru and the wider CRA 3 fishery, this highlights the need for integrated catchment-to- coast management addressing land-derived sediment inputs and protecting coastal nursery habitats. From a Te Ao Māori perspective, sedimentation represents a disruption to whakapapa relationships with Tangaroa and a weakening of mauri in coastal ecosystems. Restoring these connections requires co-governance frameworks that embed mātauranga Māori, empower kaitiaki-led monitoring and rāhui, and address the cumulative impacts of land-use intensification and repeated cyclone events on ecosystem resilience in Te Tairāwhiti.

year: 2025