title: Isomerism of Complexes Containing Thiourea Dianion Ligands

authors: Spenceley, Jane Estelle

subjects: Thiourea

abstract: This thesis reports the synthesis and characterisation of eight new platinum thiourea complexes. Thiourea dianion complexes of the type (Ph₃P)₂PtSC(=NR)NPh, R=Me, Et, Prⁿ, Prⁱ, Buⁿ and (Ph₃P)₂PtSC(=NPh)NR R=Buͭ , p-tol, and the thiourea monoanion complex of the type [(Ph₃P)₂PtSC(=NEtH)NPh]⁺ were synthesised. This research confirms the prediction made by Henderson et al that asymmetrically substituted thiourea dianion complexes could form isomers. NMR studies show that the kinetically favoured isomer is formed initially, and then undergoes a solution phase isomerisation process to form the thermodynamically favoured isomer. Evidence that this isomerisation is affected by difference in substituent size and the energy difference between the two structures was obtained both experimentally, by use of NMR spectroscopy techniques, and theoretically using DFT calculations. Theoretically optimised geometries of each isomer allowed the calculation of ΔG(GPtrem-GPtadj) for each pair. NMR techniques were used to monitor the isomerisation process, which was clearly visible in both ¹H and ³¹P spectra. The relative substituent size, difference in energy between the two structures and rate of isomerisation appear to be proportional to each other. The greater the substituent size difference, the greater the difference in energy and faster the rate of isomerisation from the kinetically favoured isomer to the thermodynamically favoured isomer.

text: Isomerism of Complexes Containing Thiourea Dianion Ligands This thesis reports the synthesis and characterisation of eight new platinum thiourea complexes. Thiourea dianion complexes of the type (Ph₃P)₂PtSC(=NR)NPh, R=Me, Et, Prⁿ, Prⁱ, Buⁿ and (Ph₃P)₂PtSC(=NPh)NR R=Buͭ , p-tol, and the thiourea monoanion complex of the type [(Ph₃P)₂PtSC(=NEtH)NPh]⁺ were synthesised. This research confirms the prediction made by Henderson et al that asymmetrically substituted thiourea dianion complexes could form isomers. NMR studies show that the kinetically favoured isomer is formed initially, and then undergoes a solution phase isomerisation process to form the thermodynamically favoured isomer. Evidence that this isomerisation is affected by difference in substituent size and the energy difference between the two structures was obtained both experimentally, by use of NMR spectroscopy techniques, and theoretically using DFT calculations. Theoretically optimised geometries of each isomer allowed the calculation of ΔG(GPtrem-GPtadj) for each pair. NMR techniques were used to monitor the isomerisation process, which was clearly visible in both ¹H and ³¹P spectra. The relative substituent size, difference in energy between the two structures and rate of isomerisation appear to be proportional to each other. The greater the substituent size difference, the greater the difference in energy and faster the rate of isomerisation from the kinetically favoured isomer to the thermodynamically favoured isomer.

year: 2014

title: Crystal structure models for the Aldaramide Units of Poly(pentaramides)

authors: Hinton, Michael R.

subjects: crystal structure

abstract: The X-ray crystal structures of seven structurally related diamides, N,N′-dihexyl- and N,N′-dimethylglutaramide, N,N′-dimethylxylaramide, N,N′-dimethyl-l-arabinaramide, N,N′-dimethylribaramide monohydrate, 2,3,4-tri-O-acetyl-N,N′-dimethylxylaramide, and 2,3,4-tri-O-acetyl-N,N′-dimethyl-l-arabinaramide, were determined. These diamides were chosen as solid-state conformational models for the diamido repeating units of the corresponding polyamides. Solid-state conformations of the two N,N-dialkyglutaramides, with no pendant groups, were compared to those of their stereochemically different trihydroxy derivatives N,N′-dimethylxylaramide, l-arabinaramide and ribaramide, and the two aforementioned tri-O-acetylpentaramides.

text: Crystal structure models for the Aldaramide Units of Poly(pentaramides) The X-ray crystal structures of seven structurally related diamides, N,N′-dihexyl- and N,N′-dimethylglutaramide, N,N′-dimethylxylaramide, N,N′-dimethyl-l-arabinaramide, N,N′-dimethylribaramide monohydrate, 2,3,4-tri-O-acetyl-N,N′-dimethylxylaramide, and 2,3,4-tri-O-acetyl-N,N′-dimethyl-l-arabinaramide, were determined. These diamides were chosen as solid-state conformational models for the diamido repeating units of the corresponding polyamides. Solid-state conformations of the two N,N-dialkyglutaramides, with no pendant groups, were compared to those of their stereochemically different trihydroxy derivatives N,N′-dimethylxylaramide, l-arabinaramide and ribaramide, and the two aforementioned tri-O-acetylpentaramides.

year: 2013

title: Lake Rotokakahi: The kakahi (Hyridella menziesi) in a general framework of lake health

authors: Butterworth, Joseph

subjects: Rotokakahi

abstract: Lake Rotokakahi is a mesotrophic lake located within the Rotorua Lakes District, North Island, New Zealand. Under the legal guardianship of the Tuhourangi and Ngati Tumatawera tribes of Te Arawa it has remained closed to the public since 1948. 

Lake Rotokakahi was last monitored regularly in 1996 under the Environment Bay of Plenty (EBOP) water quality monitoring programme with only the lake outlet (Te Wairoa Stream) being monitored since that time. Water quality data collected up to 1996 suggests that there may be degradation of water quality in the lake, as indicated by declining levels of dissolved oxygen in the bottom waters.

 Lake Rotokakahi steeped in historical significance, as well as having major cultural and recreational values was well known for its abundant resources and as the name suggests, particularly for its massive supply of the freshwater mussel or kakahi (Hyridella menziesi). Freshwater mussel species worldwide are in decline however little is known on factors controlling kakahi abundance and distribution. 

The overarching objective of this thesis is update water quality data last monitored in Lake Rotokakahi in 1996 while also identifying key environmental variables thought to influence kakahi populations.  This objective is underpinned by a number of aims that include:
 	Establishment of a 12-13 month water quality programme within Lake Rotokakahi so that data is obtained for comparisons with previous water quality data (pre-1997) to allow assessment of whether there have been water quality changes in the lake.
 	Conduct a population survey of the resident kakahi population examining possible environmental factors influencing their populations.
 	Present an oral history of Lake Rotokakahi focusing on its historical significance, water quality, and collection of kairoto (food collected form lakes).

from the 18 September 2006 to 14 September 2007 monthly water sampling was carried out at a mid lake station, the lake outflow and inflow for measures of nutrients, phytoplankton, zooplankton and chlorophyll a. Vertical profiles of temperature dissolved oxygen and chlorophyll fluorescence were also taken on various part of Lake Rotokakahi.

A lengthened period of anoxia in the bottom waters during thermal stratification was recorded with increased levels of chlorophyll a in winter and reduced secchi disk depth indicating an increase in phytoplankton biomass. Nutrient concentrations remain moderate relative to historical data. On going water quality monitoring on Lake Rotokakahi is recommended to further evaluate the extent of which water quality change is occurring. This will provide a better understanding of how Lake Rotokakahi can be best managed to further preserve the lake.

On 1 March and 20 April kakahi were sampled at five sites. Large kakahi densities were distributed predominantly in depths above the hypolimnion. Chlorophyll a fluorescence and dissolved oxygen were found to be the best correlates for kakahi density and biomass respectively. Low dissolved oxygen concentrations in the hypolimnion are thought to restrict kakahi distributions to above the thermocline in periods of hypolimnetic anoxia.

text: Lake Rotokakahi: The kakahi (Hyridella menziesi) in a general framework of lake health Lake Rotokakahi is a mesotrophic lake located within the Rotorua Lakes District, North Island, New Zealand. Under the legal guardianship of the Tuhourangi and Ngati Tumatawera tribes of Te Arawa it has remained closed to the public since 1948. 

Lake Rotokakahi was last monitored regularly in 1996 under the Environment Bay of Plenty (EBOP) water quality monitoring programme with only the lake outlet (Te Wairoa Stream) being monitored since that time. Water quality data collected up to 1996 suggests that there may be degradation of water quality in the lake, as indicated by declining levels of dissolved oxygen in the bottom waters.

 Lake Rotokakahi steeped in historical significance, as well as having major cultural and recreational values was well known for its abundant resources and as the name suggests, particularly for its massive supply of the freshwater mussel or kakahi (Hyridella menziesi). Freshwater mussel species worldwide are in decline however little is known on factors controlling kakahi abundance and distribution. 

The overarching objective of this thesis is update water quality data last monitored in Lake Rotokakahi in 1996 while also identifying key environmental variables thought to influence kakahi populations.  This objective is underpinned by a number of aims that include:
 	Establishment of a 12-13 month water quality programme within Lake Rotokakahi so that data is obtained for comparisons with previous water quality data (pre-1997) to allow assessment of whether there have been water quality changes in the lake.
 	Conduct a population survey of the resident kakahi population examining possible environmental factors influencing their populations.
 	Present an oral history of Lake Rotokakahi focusing on its historical significance, water quality, and collection of kairoto (food collected form lakes).

from the 18 September 2006 to 14 September 2007 monthly water sampling was carried out at a mid lake station, the lake outflow and inflow for measures of nutrients, phytoplankton, zooplankton and chlorophyll a. Vertical profiles of temperature dissolved oxygen and chlorophyll fluorescence were also taken on various part of Lake Rotokakahi.

A lengthened period of anoxia in the bottom waters during thermal stratification was recorded with increased levels of chlorophyll a in winter and reduced secchi disk depth indicating an increase in phytoplankton biomass. Nutrient concentrations remain moderate relative to historical data. On going water quality monitoring on Lake Rotokakahi is recommended to further evaluate the extent of which water quality change is occurring. This will provide a better understanding of how Lake Rotokakahi can be best managed to further preserve the lake.

On 1 March and 20 April kakahi were sampled at five sites. Large kakahi densities were distributed predominantly in depths above the hypolimnion. Chlorophyll a fluorescence and dissolved oxygen were found to be the best correlates for kakahi density and biomass respectively. Low dissolved oxygen concentrations in the hypolimnion are thought to restrict kakahi distributions to above the thermocline in periods of hypolimnetic anoxia.

year: 2008