title: Gold(I) complexes and co oxidation catalysts

authors: Mathieson, Trevor J.

abstract: Isonitrile gold(I) nitrates, (RNC)AuNO₃ (R = Buᵗ, Et or Xy) have been prepared and fully characterised. These join the rare set of gold(I) species exhibiting ligation to oxygen and are the first examples of gold(I) bonded to both carbon and oxygen. Molecular aggregations of the monomeric units were revealed by X-ray crystal structure determinations. The aggregations are the result of secondary Au--Au interactions. These interactions are also apparent in the structures of the analogous complexes (RNC)AuCl (R = Et or Xy), which were characterised for comparative purposes.

(EtNC)AuCl and (BuᵗNC)AuNO₃ formed zig-zag chain structures from which the other unprecedented structures can be derived. (EtNC)AuNO₃ formed a concertinaed chain, (XyNC)AuNO₃ (1) a compressed chain and (XyNC)AuCl a tetrameric chain. The formations of these supramolecular motifs are attributed to various steric and electronic ligand influences on the inherent Au--Au attraction. In addition, intermolecular π-π contacts were observed for the (XyNC)AuX (X = Cl or NO₃) structures.

In each instance, the Au--Au interactions for (RNC)AuNO₃ were significantly shorter than those of the analogous (RNC)AuCl structure. The results demonstrated that the non-polarisable nitrate anion enhances the Au--Au attraction. This is contrary to previous theoretical calculations, which predict that soft anions enhance the Au--Au attraction. The structure of the ionic [(XyNC)₂Au]⁺NO₃- complex was also characterised. This did not exhibit Au--Au contacts; the packing structure was instead based on infinite π-π stacking.

The potential of gold(I) complexes as precursors to supported gold catalysts was assessed. The complexes were adsorbed (from a solution phase) onto transition metal oxide supports which were subsequently vacuum dried and calcined. Scanning Electron Microscopy (SEM) revealed a range of gold particle sizes on the calcined materials. The extent of gold dispersion was dependent on the chemical properties of the complex employed.

The use of the stable (Ph₃P)AuCl, (Ph₃P)AuMe and (BuᵗNC)AuCl complexes resulted in relatively large gold particles (20-200 nm). In the case of (Ph₃P)AuMe, metallic gold crystals were observed. Under ambient conditions these materials were inactive for CO oxidation. Under the same testing conditions, efficient catalytic CO oxidation was observed over materials prepared by using the unstable (BuᵗNC)AuNO₃ complex as a precursor. The gold particles on the active catalyst were too small to be resolved by SEM.

The observed CO oxidation activity was proposed to be a two-component catalytic reaction involving gold nano-particles in intimate contact with a reducible oxide support. Reactant inhibition, which is commonly observed for catalysts with inert supports, is avoided in this system. This form of catalysis has received considerable recent attention for the CO oxidation reaction and provides guidance for attempts to enhance other heterogeneous catalytic processes.

text: Gold(I) complexes and co oxidation catalysts Isonitrile gold(I) nitrates, (RNC)AuNO₃ (R = Buᵗ, Et or Xy) have been prepared and fully characterised. These join the rare set of gold(I) species exhibiting ligation to oxygen and are the first examples of gold(I) bonded to both carbon and oxygen. Molecular aggregations of the monomeric units were revealed by X-ray crystal structure determinations. The aggregations are the result of secondary Au--Au interactions. These interactions are also apparent in the structures of the analogous complexes (RNC)AuCl (R = Et or Xy), which were characterised for comparative purposes.

(EtNC)AuCl and (BuᵗNC)AuNO₃ formed zig-zag chain structures from which the other unprecedented structures can be derived. (EtNC)AuNO₃ formed a concertinaed chain, (XyNC)AuNO₃ (1) a compressed chain and (XyNC)AuCl a tetrameric chain. The formations of these supramolecular motifs are attributed to various steric and electronic ligand influences on the inherent Au--Au attraction. In addition, intermolecular π-π contacts were observed for the (XyNC)AuX (X = Cl or NO₃) structures.

In each instance, the Au--Au interactions for (RNC)AuNO₃ were significantly shorter than those of the analogous (RNC)AuCl structure. The results demonstrated that the non-polarisable nitrate anion enhances the Au--Au attraction. This is contrary to previous theoretical calculations, which predict that soft anions enhance the Au--Au attraction. The structure of the ionic [(XyNC)₂Au]⁺NO₃- complex was also characterised. This did not exhibit Au--Au contacts; the packing structure was instead based on infinite π-π stacking.

The potential of gold(I) complexes as precursors to supported gold catalysts was assessed. The complexes were adsorbed (from a solution phase) onto transition metal oxide supports which were subsequently vacuum dried and calcined. Scanning Electron Microscopy (SEM) revealed a range of gold particle sizes on the calcined materials. The extent of gold dispersion was dependent on the chemical properties of the complex employed.

The use of the stable (Ph₃P)AuCl, (Ph₃P)AuMe and (BuᵗNC)AuCl complexes resulted in relatively large gold particles (20-200 nm). In the case of (Ph₃P)AuMe, metallic gold crystals were observed. Under ambient conditions these materials were inactive for CO oxidation. Under the same testing conditions, efficient catalytic CO oxidation was observed over materials prepared by using the unstable (BuᵗNC)AuNO₃ complex as a precursor. The gold particles on the active catalyst were too small to be resolved by SEM.

The observed CO oxidation activity was proposed to be a two-component catalytic reaction involving gold nano-particles in intimate contact with a reducible oxide support. Reactant inhibition, which is commonly observed for catalysts with inert supports, is avoided in this system. This form of catalysis has received considerable recent attention for the CO oxidation reaction and provides guidance for attempts to enhance other heterogeneous catalytic processes.

year: 1998

title: First international workshop on using ontologies in interactive systems, ONTORACT'08

authors: Bouamrane, Matt-Mouley

abstract: The aim of the workshop is to hold a multidisciplinary event bringing together researchers and practitioners to share their experiences of using ontologies for managing user interaction and interactive systems.

text: First international workshop on using ontologies in interactive systems, ONTORACT'08 The aim of the workshop is to hold a multidisciplinary event bringing together researchers and practitioners to share their experiences of using ontologies for managing user interaction and interactive systems.

year: 2008

title: Death and homelessness on the streets of Aotearoa New Zealand: Sustaining life

authors: Charvin-Fabre, Sandrine

abstract: In high-income countries, homeless people die 20 to 35 years earlier than domiciled populations. Despite this enduring reality, the issue of death inequality remains underexplored, especially in indigenous homeless contexts, facing the ongoing effects of colonisation. This study centres on the perspectives and aspirations of a Māori street homeless community, known as the “Peeps”. Its objective is twofold: to spotlight to unjust, untimely, and avoidable mortality impacting homeless communities in Aotearoa New Zealand, and to understand how life can be sustained against the adversity of street life. The thesis diverges from conventional public health approaches, which often dichotomise early deaths prevention through improved healthcare access during homelessness, and palliative care provision at the end of life of homeless people. This thesis explores “the temporal space of life prior to death”. Within that temporal realm, the omnipresent “risk of dying” that infiltrates the lives of homeless people, disrupting the linear progression toward death observed in domiciled populations, is recognised. This temporal space is understood as a zone of uncertainty and potentiality, wherein complex life-death dynamics operate, revealing broader political, societal and cultural tensions. This study encountered significant challenges, including the dearth of prior death-related research in Māori homeless contexts, and my non-Māori identity. In response, an indeterminate approach, rooted in relational ethics and complexity and systems thinking — aligned with Māori worldviews — was adopted.  

Part I of the thesis is conceptual and contextual. Part II invites the readers into the fragile “temporal space of life prior to death” and the cyclical research process. Cycle 1 focuses on understanding the local context of death inequality, through relational fieldwork and statistical analysis of coroners’ reports. This analysis uncovers a 30-year life expectancy disparity with domiciled populations, exacerbated by three-quarters of avoidable mortality, mainly due to chronic conditions and suicide. Subsequent cycles sustain relational fieldwork, using collaborative and critical performance ethnography. Cycle 2 reveals the Peeps’ resistance to access healthcare, rooted in experiences of transgenerational trauma and marginalisation of Māori beliefs and values in relation to death and dying within mainstream healthcare institutions. Collaboration with the Peeps leads to the co-creation of a drama, intended to initiate conversations with health professionals from the Peeps’ perspectives and aspirations, to improve the quality of care. This cycle also highlights the impact of disconnection processes with whānau (family, extended family) experienced by the Peeps. Progressing further, cycle 3 illuminates healing processes with whānau using Advance Care Planning, envisioned as a relational space, providing the Peeps with a sense of belonging, and spiritual continuity in the perspective of death and dying. 
 
In addition to shedding light on the profound death inequality that affect Māori homeless people, this thesis argues for homelessness to be recognised as “complex life-threatening conditions associated with serious-related health suffering”. Accordingly, the thesis advocates the shift toward comprehensive care, inclusive of a concurrent prevention and palliation approach over the course of homelessness, to mitigate its impact on the lives of Māori homeless people and enhance holistic wellbeing.

text: Death and homelessness on the streets of Aotearoa New Zealand: Sustaining life In high-income countries, homeless people die 20 to 35 years earlier than domiciled populations. Despite this enduring reality, the issue of death inequality remains underexplored, especially in indigenous homeless contexts, facing the ongoing effects of colonisation. This study centres on the perspectives and aspirations of a Māori street homeless community, known as the “Peeps”. Its objective is twofold: to spotlight to unjust, untimely, and avoidable mortality impacting homeless communities in Aotearoa New Zealand, and to understand how life can be sustained against the adversity of street life. The thesis diverges from conventional public health approaches, which often dichotomise early deaths prevention through improved healthcare access during homelessness, and palliative care provision at the end of life of homeless people. This thesis explores “the temporal space of life prior to death”. Within that temporal realm, the omnipresent “risk of dying” that infiltrates the lives of homeless people, disrupting the linear progression toward death observed in domiciled populations, is recognised. This temporal space is understood as a zone of uncertainty and potentiality, wherein complex life-death dynamics operate, revealing broader political, societal and cultural tensions. This study encountered significant challenges, including the dearth of prior death-related research in Māori homeless contexts, and my non-Māori identity. In response, an indeterminate approach, rooted in relational ethics and complexity and systems thinking — aligned with Māori worldviews — was adopted.  

Part I of the thesis is conceptual and contextual. Part II invites the readers into the fragile “temporal space of life prior to death” and the cyclical research process. Cycle 1 focuses on understanding the local context of death inequality, through relational fieldwork and statistical analysis of coroners’ reports. This analysis uncovers a 30-year life expectancy disparity with domiciled populations, exacerbated by three-quarters of avoidable mortality, mainly due to chronic conditions and suicide. Subsequent cycles sustain relational fieldwork, using collaborative and critical performance ethnography. Cycle 2 reveals the Peeps’ resistance to access healthcare, rooted in experiences of transgenerational trauma and marginalisation of Māori beliefs and values in relation to death and dying within mainstream healthcare institutions. Collaboration with the Peeps leads to the co-creation of a drama, intended to initiate conversations with health professionals from the Peeps’ perspectives and aspirations, to improve the quality of care. This cycle also highlights the impact of disconnection processes with whānau (family, extended family) experienced by the Peeps. Progressing further, cycle 3 illuminates healing processes with whānau using Advance Care Planning, envisioned as a relational space, providing the Peeps with a sense of belonging, and spiritual continuity in the perspective of death and dying. 
 
In addition to shedding light on the profound death inequality that affect Māori homeless people, this thesis argues for homelessness to be recognised as “complex life-threatening conditions associated with serious-related health suffering”. Accordingly, the thesis advocates the shift toward comprehensive care, inclusive of a concurrent prevention and palliation approach over the course of homelessness, to mitigate its impact on the lives of Māori homeless people and enhance holistic wellbeing.

year: 2024