title: The Chemistry of Cycloaurated Complexes

authors: Kilpin, Kelly Joan

subjects: gold

abstract: New cycloaurated complexes have been synthesised and characterised. The biological and catalytic activity (in the addition of 2-methylfuran to methyl vinyl ketone) of selected complexes was evaluated. New complexes reported in this thesis where fully characterised by NMR (¹H, ¹³C and ³¹P when appropriate) and IR spectroscopy, ESI-mass spectrometry and elemental analysis.

The simple cycloaurated iminophosphoranes (2-AuCl₂C₆H₄)Ph₂P=N-R (R = (R,S)-CHMePh, (S)-CHMePh, p-C₆H₄F or But) were synthesised by the reaction of the appropriate ortho-mercurated compound with [Me₄N][AuCl₄] and [Me₄N]Cl in acetonitrile; the complex (2-AuCl₂C₆H₄)Ph₂P=N-(S)-CHMePh was structurally characterised. The cis chloride ligands on the complexes were replaced by chelating dianionic ligands such as thiosalicylate and catecholate - the resulting bis-metallacyclic complexes have a better anti-tumour activity (against P388 murine leukemia cells) than the parent dichlorides. The nitrogen-gold coordinate bond is relatively robust and is not cleaved by cyanide or dithiocarbamate ligands. The reaction of (2-AuCl₂C₆H₄)Ph₂P=N-Ph with PPh₃ results in substitution of the chloride ligand trans to the nitrogen (shown by an X-ray crystal structure). Both the endo ((2-AuCl₂C₆H₄)Ph₂P=NC(O)Ph) and exo ((2-AuCl₂C₆H₄)C(O)N=PPh₃) cycloaurated isomers of the stabilised iminophosphorane Ph₃P=NC(O)Ph were synthesised and structurally characterised.

Cycloaurated Ph₃P=S and Ph₃P=Se were synthesised by a transmetallation reaction from 2-Hg[(C₆H₄)P(E)Ph₂]₂ (E = S or Se). The synthesis of cycloaurated Ph₃P=O by an analogous method was unsuccessful. PhP(S)(NEt₂)₂ was also cycloaurated via a transmetallation reaction. X-ray crystallography confirmed the sulfur (not the nitrogen) was coordinated to the gold centre. The complexes show a similar stability and reactivity to the C,N cycloaurated species - the cis chloride ligands can be replaced by the chelating thiosalicylate ligand. Again the bis-metallacyclic species showed better biological activity than the parent dichloride. 

The direct reaction of the 2-pyridyl sulfonamide ligands 2-(C₅H₅N)CH₂NHSO₂R (R = p-tolyl, Ph or Me), 2-(C₅H₅N)CH₂CH₂NHSO₂R (R = p-tolyl or Ph) or 8-(p-tosylamino)quinoline with refluxing aqueous H[AuCl₄] gave N,N' coordinated complexes containing a five- or six-membered cycloaurated ring. The cycloaurated complexes derived from the ligands 2-(C₅H₅N)CH₂NHSO₂Me and 8-(p-tosylamino)quinoline were structurally characterised. The cycloaurated N,N' systems were not as stable as the C,N systems - reaction with reducing agents led to reduction of Au(III) to Au(I) and elemental gold. 

The 2-pyridine thiocarboxamide ligands 2-(C₅H₅N)C(S)NHR (R= p-tolyl, CH₂Ph, Me, p-C₆H₅OMe) also underwent direct cycloauration upon reaction with H[AuCl₄]. Coordination via the pyridyl nitrogen and sulfur atom was confirmed by an X-ray crystal structure of cycloaurated 2-(C₅H₅N)C(S)NHCH₂Ph. The N,S cycloaurated systems show poor stability in solution and decompose relatively quickly so applications are limited. The ligand with a 2 pyridyl substituent reacted with H[AuCl₄] in a different manner. Instead of cycloauration, the ligand was oxidised and an internal cyclisation occurred to give a 1,2,4-thiadiazolo[2,3-a]pyridinium heterocyclic ring. 

The reaction of the cycloaurated dichloride complexes (2-benzylpyridine)AuCl₂ and (2-AuCl₂C₆H₄)Ph₂P=N-Ph with the tripodal Kläui ligands (Na[(C₅H₅)Co{P(O)R₂}₃], R = OMe or OEt) and Tl[BF₄] resulted in the formation of cationic gold(III) salts. In the solid state the Kläui ligand is strongly coordinated through two of the three oxygen atoms, and weakly by the third, giving the gold a distorted square pyramidal geometry. In solution there is rapid interchange between the coordinated and non-coordinated oxygen atoms.

text: The Chemistry of Cycloaurated Complexes New cycloaurated complexes have been synthesised and characterised. The biological and catalytic activity (in the addition of 2-methylfuran to methyl vinyl ketone) of selected complexes was evaluated. New complexes reported in this thesis where fully characterised by NMR (¹H, ¹³C and ³¹P when appropriate) and IR spectroscopy, ESI-mass spectrometry and elemental analysis.

The simple cycloaurated iminophosphoranes (2-AuCl₂C₆H₄)Ph₂P=N-R (R = (R,S)-CHMePh, (S)-CHMePh, p-C₆H₄F or But) were synthesised by the reaction of the appropriate ortho-mercurated compound with [Me₄N][AuCl₄] and [Me₄N]Cl in acetonitrile; the complex (2-AuCl₂C₆H₄)Ph₂P=N-(S)-CHMePh was structurally characterised. The cis chloride ligands on the complexes were replaced by chelating dianionic ligands such as thiosalicylate and catecholate - the resulting bis-metallacyclic complexes have a better anti-tumour activity (against P388 murine leukemia cells) than the parent dichlorides. The nitrogen-gold coordinate bond is relatively robust and is not cleaved by cyanide or dithiocarbamate ligands. The reaction of (2-AuCl₂C₆H₄)Ph₂P=N-Ph with PPh₃ results in substitution of the chloride ligand trans to the nitrogen (shown by an X-ray crystal structure). Both the endo ((2-AuCl₂C₆H₄)Ph₂P=NC(O)Ph) and exo ((2-AuCl₂C₆H₄)C(O)N=PPh₃) cycloaurated isomers of the stabilised iminophosphorane Ph₃P=NC(O)Ph were synthesised and structurally characterised.

Cycloaurated Ph₃P=S and Ph₃P=Se were synthesised by a transmetallation reaction from 2-Hg[(C₆H₄)P(E)Ph₂]₂ (E = S or Se). The synthesis of cycloaurated Ph₃P=O by an analogous method was unsuccessful. PhP(S)(NEt₂)₂ was also cycloaurated via a transmetallation reaction. X-ray crystallography confirmed the sulfur (not the nitrogen) was coordinated to the gold centre. The complexes show a similar stability and reactivity to the C,N cycloaurated species - the cis chloride ligands can be replaced by the chelating thiosalicylate ligand. Again the bis-metallacyclic species showed better biological activity than the parent dichloride. 

The direct reaction of the 2-pyridyl sulfonamide ligands 2-(C₅H₅N)CH₂NHSO₂R (R = p-tolyl, Ph or Me), 2-(C₅H₅N)CH₂CH₂NHSO₂R (R = p-tolyl or Ph) or 8-(p-tosylamino)quinoline with refluxing aqueous H[AuCl₄] gave N,N' coordinated complexes containing a five- or six-membered cycloaurated ring. The cycloaurated complexes derived from the ligands 2-(C₅H₅N)CH₂NHSO₂Me and 8-(p-tosylamino)quinoline were structurally characterised. The cycloaurated N,N' systems were not as stable as the C,N systems - reaction with reducing agents led to reduction of Au(III) to Au(I) and elemental gold. 

The 2-pyridine thiocarboxamide ligands 2-(C₅H₅N)C(S)NHR (R= p-tolyl, CH₂Ph, Me, p-C₆H₅OMe) also underwent direct cycloauration upon reaction with H[AuCl₄]. Coordination via the pyridyl nitrogen and sulfur atom was confirmed by an X-ray crystal structure of cycloaurated 2-(C₅H₅N)C(S)NHCH₂Ph. The N,S cycloaurated systems show poor stability in solution and decompose relatively quickly so applications are limited. The ligand with a 2 pyridyl substituent reacted with H[AuCl₄] in a different manner. Instead of cycloauration, the ligand was oxidised and an internal cyclisation occurred to give a 1,2,4-thiadiazolo[2,3-a]pyridinium heterocyclic ring. 

The reaction of the cycloaurated dichloride complexes (2-benzylpyridine)AuCl₂ and (2-AuCl₂C₆H₄)Ph₂P=N-Ph with the tripodal Kläui ligands (Na[(C₅H₅)Co{P(O)R₂}₃], R = OMe or OEt) and Tl[BF₄] resulted in the formation of cationic gold(III) salts. In the solid state the Kläui ligand is strongly coordinated through two of the three oxygen atoms, and weakly by the third, giving the gold a distorted square pyramidal geometry. In solution there is rapid interchange between the coordinated and non-coordinated oxygen atoms.

year: 2009

title: Identification of quantitative trait loci for dynamic and steady-state photosynthetic traits in a barley mapping population

authors: Salter, William T.

subjects: Science & Technology

abstract: Enhancing the photosynthetic induction response to fluctuating light has been suggested as a key target for improvement in crop breeding programmes, with the potential to substantially increase whole-canopy carbon assimilation and contribute to crop yield potential. Rubisco activation may be the main physiological process that will allow us to achieve such a goal. In this study, we assessed the phenotype of Rubisco activation rate in a doubled haploid (DH) barley mapping population [131 lines from a Yerong/Franklin (Y/F) cross] after a switch from moderate to saturating light. Rates of Rubisco activation were found to be highly variable across the mapping population, with a median activation rate of 0.1 min−1 in the slowest genotype and 0.74 min−1 in the fastest genotype. A unique quantitative trait locus (QTL) for Rubisco activation rate was identified on chromosome 7H. This is the first report on the identification of a QTL for Rubisco activation rate in planta and the discovery opens the door to marker-assisted breeding to improve whole-canopy photosynthesis of barley. This also suggests that genetic factors other than the previously characterized Rubisco activase (RCA) isoforms on chromosome 4H control Rubisco activity. Further strength is given to this finding as this QTL co-localized with QTLs identified for steady-state photosynthesis and stomatal conductance. Several other distinct QTLs were identified for these steady-state traits, with a common overlapping QTL on chromosome 2H, and distinct QTLs for photosynthesis and stomatal conductance identified on chromosomes 4H and 5H, respectively. Future work should aim to validate these QTLs under field conditions so that they can be used to aid plant breeding efforts.

text: Identification of quantitative trait loci for dynamic and steady-state photosynthetic traits in a barley mapping population Enhancing the photosynthetic induction response to fluctuating light has been suggested as a key target for improvement in crop breeding programmes, with the potential to substantially increase whole-canopy carbon assimilation and contribute to crop yield potential. Rubisco activation may be the main physiological process that will allow us to achieve such a goal. In this study, we assessed the phenotype of Rubisco activation rate in a doubled haploid (DH) barley mapping population [131 lines from a Yerong/Franklin (Y/F) cross] after a switch from moderate to saturating light. Rates of Rubisco activation were found to be highly variable across the mapping population, with a median activation rate of 0.1 min−1 in the slowest genotype and 0.74 min−1 in the fastest genotype. A unique quantitative trait locus (QTL) for Rubisco activation rate was identified on chromosome 7H. This is the first report on the identification of a QTL for Rubisco activation rate in planta and the discovery opens the door to marker-assisted breeding to improve whole-canopy photosynthesis of barley. This also suggests that genetic factors other than the previously characterized Rubisco activase (RCA) isoforms on chromosome 4H control Rubisco activity. Further strength is given to this finding as this QTL co-localized with QTLs identified for steady-state photosynthesis and stomatal conductance. Several other distinct QTLs were identified for these steady-state traits, with a common overlapping QTL on chromosome 2H, and distinct QTLs for photosynthesis and stomatal conductance identified on chromosomes 4H and 5H, respectively. Future work should aim to validate these QTLs under field conditions so that they can be used to aid plant breeding efforts.

year: 2020

title: Ngā tohu o te taiao: Observing signs of the natural world to identify seastar over-abundance as a detriment to shellfish survival in Ōhiwa Harbour, Aotearoa New Zealand

authors: Paul-Burke, Kura

subjects: Tohu

abstract: Māori understandings and experiences of the natural world encompass not only what is known but how it is known, and the intergenerational connectedness of that knowledge with the environments from which it is derived. Ngā tohu o te taiao (hereafter ‘tohu’), or the cultural and environmental signs and indicators of the natural world, are widely used by kaitiaki or local practitioners to identify trends or changes in the state or health of marine taonga (culturally important) species and their associated environments (Paul-Burke, 2017). Māori worldviews position humans within nature and focus on ways in which cultural understandings and intergenerational connections between people and their bio-physical contexts assist in the retention and protection of biodiversity and ecologically sustainable ecosystems (Lyver et al., 2016). Tohu are a fundamental expression of kaitiakitanga or active guardianship and are based on the primal instinct of survival and recognising that in order to survive one must pay attention to the natural signs and signals thoughtfully, so as to manage our mahinga kai (food harvesting area) and ourselves into the future (Paul-Burke et al., 2020). This article considers the example of the over-abundant eleven-armed seastar (pātangaroa, Coscinasterias muricata; hereafter ‘seastar’) predating on culturally and ecologically important shellfish populations in a traditional mahinga kai of Ōhiwa Harbour in the Bay of Plenty region of Aotearoa/New Zealand. The over-abundance of seastars was considered a contemporary tohu of a degrading harbour. It was deemed imperative by iwi (tribe) members that a trial using quantitative methods to investigate predation pressure of seastars on the green-lipped mussel (kuku or kūtai, Perna canaliculus) population be conducted in the harbour. Between September 2018 and February 2019 field trials were undertaken that prioritised mātauranga Māori (Māori knowledge) alongside marine science to assist with a better understanding of the degrading harbour. It was hoped that the research would help and promote recovery, in particular but not limited to, the once abundant but now severely reduced mussel reefs in the soft-mud-bottomed harbour.

text: Ngā tohu o te taiao: Observing signs of the natural world to identify seastar over-abundance as a detriment to shellfish survival in Ōhiwa Harbour, Aotearoa New Zealand Māori understandings and experiences of the natural world encompass not only what is known but how it is known, and the intergenerational connectedness of that knowledge with the environments from which it is derived. Ngā tohu o te taiao (hereafter ‘tohu’), or the cultural and environmental signs and indicators of the natural world, are widely used by kaitiaki or local practitioners to identify trends or changes in the state or health of marine taonga (culturally important) species and their associated environments (Paul-Burke, 2017). Māori worldviews position humans within nature and focus on ways in which cultural understandings and intergenerational connections between people and their bio-physical contexts assist in the retention and protection of biodiversity and ecologically sustainable ecosystems (Lyver et al., 2016). Tohu are a fundamental expression of kaitiakitanga or active guardianship and are based on the primal instinct of survival and recognising that in order to survive one must pay attention to the natural signs and signals thoughtfully, so as to manage our mahinga kai (food harvesting area) and ourselves into the future (Paul-Burke et al., 2020). This article considers the example of the over-abundant eleven-armed seastar (pātangaroa, Coscinasterias muricata; hereafter ‘seastar’) predating on culturally and ecologically important shellfish populations in a traditional mahinga kai of Ōhiwa Harbour in the Bay of Plenty region of Aotearoa/New Zealand. The over-abundance of seastars was considered a contemporary tohu of a degrading harbour. It was deemed imperative by iwi (tribe) members that a trial using quantitative methods to investigate predation pressure of seastars on the green-lipped mussel (kuku or kūtai, Perna canaliculus) population be conducted in the harbour. Between September 2018 and February 2019 field trials were undertaken that prioritised mātauranga Māori (Māori knowledge) alongside marine science to assist with a better understanding of the degrading harbour. It was hoped that the research would help and promote recovery, in particular but not limited to, the once abundant but now severely reduced mussel reefs in the soft-mud-bottomed harbour.

year: 2022-03-28