title: Electrospray-friendly ligands for the mass spectral analysis of transition-metal complexes

authors: Decker, Corry

abstract: The key aim of this project was to develop the concept of electrospray-friendly ligands as a new ionisation method for the analysis of neutral metal complexes by electrospray mass spectrometry (ESMS). This involved introducing active functional groups into traditional ligands which do not otherwise undergo chemical ionisation under ESMS conditions.

Electrospray-friendly ligands (as illustrated above for PPh₃ derivatives) were incorporated into a series of metal carbonyl complexes of Mo, Fe and Ru, metal halide complexes of Pd, Pt and Au, and a number of zero-valent complexes of Pt and Pd. All carbonyl complexes with ES-friendly phosphine, arsine and stibine ligands ionised by protonation, yielding strong [M + H]⁺ ions as the only signals in the spectrum. The metal halide complexes followed the known halide-loss mechanism. Pt(0) and Pd(0) complexes did not require functionalised ligands, as their PPh₃ derivatives already gave [M +H]⁺ ions. Mo and W carbonyl complexes of the two ‘naturally’ electrospray friendly ligands tpa (tpa = 1,3,5-triaza-7-phosphaadamantane) and tcep [tcep = tris(2-cyanoethyl)phosphine] could also be studied readily by ESMS. While all tpa complexes gave [M + H]⁺ ions, complexes of tcep preferred ionisation by NH₄⁺. The ionisation efficiencies of selected ligands and complexes are discussed.

Thiolate complexes of Ni, Pd, Pt, Au and Hg were prepared using the ligands SC₆H₄OMe-p (S*) and p-SC₅H₄N (S•), but only the S•-complexes reliably underwent the protonation-type mechanism. The Cd-thiolate complexes [Cd₄(SPh)₁₀]²⁻, [S₄Cd₁₀(SPh)₁₆]⁴⁻ and [S₄Cd₁₀(SPh)₂₈]²⁻ underwent rapid ligand exchange with S*, but yielded insoluble products with S•. The complexes [Pt₂(μ-S)₂(L)₂] (L = PPh₃, P*, P**, P***. P•. As***¹) were prepared, and by means of ESMS, aspects of ligand exchange as well as reactivity towards other metal centres were investigated.

Isonitrile derivatives of [Fe₃(CO)₁₂] and [Ru₃CO)₁₂] were prepared by ligand exchange with CNPh, CNC₆H₄OMe-p (CNPh*) and tosylmethylisocyanide. Substitution was observed for up to six CO ligands. Pyrolysis of [Fe₃(CO)₁₁(L)] and [Fe₃(CO)₁₀(L)₂] (L =CNPh, CNPh*) led to the products [Fe₃(CO)₉(μ₃ - η²-L)] and [Fe₃(CO)₈(μ₃-η²-L) (L)], respectively. All complexes could be studied by ESMS as their [M + H]⁺, [M + MeO]⁻ or  [M – H]⁻ ions, depending on the exact nature of the analyte. [Fe₃(CO)₁₀(CNPh)₂] was characterised structurally (below) and revealed an unprecedented substitution pattern, together with unexpected partial disorder in the metal framework.

Detection by ESMS of products of the type [Ru₄(CO) ₁₄₋ₙ(L)ₙ] (L = CNPh, CNPh*; n =2-4) in the reactions with ruthenium carbonyl led to the isolation and structural characterisation of [Ru₄(CO)₁₂(CNPh)₄], which is the only fully characterised isonitrile derivative of [Ru₃(CO)₁₂] with four metal atoms and exhibits an unusual imine-type bonding mode for the bridging isonitrile ligands.
________________________
¹As*** = As(C₆H₄OMe-p)₃

text: Electrospray-friendly ligands for the mass spectral analysis of transition-metal complexes The key aim of this project was to develop the concept of electrospray-friendly ligands as a new ionisation method for the analysis of neutral metal complexes by electrospray mass spectrometry (ESMS). This involved introducing active functional groups into traditional ligands which do not otherwise undergo chemical ionisation under ESMS conditions.

Electrospray-friendly ligands (as illustrated above for PPh₃ derivatives) were incorporated into a series of metal carbonyl complexes of Mo, Fe and Ru, metal halide complexes of Pd, Pt and Au, and a number of zero-valent complexes of Pt and Pd. All carbonyl complexes with ES-friendly phosphine, arsine and stibine ligands ionised by protonation, yielding strong [M + H]⁺ ions as the only signals in the spectrum. The metal halide complexes followed the known halide-loss mechanism. Pt(0) and Pd(0) complexes did not require functionalised ligands, as their PPh₃ derivatives already gave [M +H]⁺ ions. Mo and W carbonyl complexes of the two ‘naturally’ electrospray friendly ligands tpa (tpa = 1,3,5-triaza-7-phosphaadamantane) and tcep [tcep = tris(2-cyanoethyl)phosphine] could also be studied readily by ESMS. While all tpa complexes gave [M + H]⁺ ions, complexes of tcep preferred ionisation by NH₄⁺. The ionisation efficiencies of selected ligands and complexes are discussed.

Thiolate complexes of Ni, Pd, Pt, Au and Hg were prepared using the ligands SC₆H₄OMe-p (S*) and p-SC₅H₄N (S•), but only the S•-complexes reliably underwent the protonation-type mechanism. The Cd-thiolate complexes [Cd₄(SPh)₁₀]²⁻, [S₄Cd₁₀(SPh)₁₆]⁴⁻ and [S₄Cd₁₀(SPh)₂₈]²⁻ underwent rapid ligand exchange with S*, but yielded insoluble products with S•. The complexes [Pt₂(μ-S)₂(L)₂] (L = PPh₃, P*, P**, P***. P•. As***¹) were prepared, and by means of ESMS, aspects of ligand exchange as well as reactivity towards other metal centres were investigated.

Isonitrile derivatives of [Fe₃(CO)₁₂] and [Ru₃CO)₁₂] were prepared by ligand exchange with CNPh, CNC₆H₄OMe-p (CNPh*) and tosylmethylisocyanide. Substitution was observed for up to six CO ligands. Pyrolysis of [Fe₃(CO)₁₁(L)] and [Fe₃(CO)₁₀(L)₂] (L =CNPh, CNPh*) led to the products [Fe₃(CO)₉(μ₃ - η²-L)] and [Fe₃(CO)₈(μ₃-η²-L) (L)], respectively. All complexes could be studied by ESMS as their [M + H]⁺, [M + MeO]⁻ or  [M – H]⁻ ions, depending on the exact nature of the analyte. [Fe₃(CO)₁₀(CNPh)₂] was characterised structurally (below) and revealed an unprecedented substitution pattern, together with unexpected partial disorder in the metal framework.

Detection by ESMS of products of the type [Ru₄(CO) ₁₄₋ₙ(L)ₙ] (L = CNPh, CNPh*; n =2-4) in the reactions with ruthenium carbonyl led to the isolation and structural characterisation of [Ru₄(CO)₁₂(CNPh)₄], which is the only fully characterised isonitrile derivative of [Ru₃(CO)₁₂] with four metal atoms and exhibits an unusual imine-type bonding mode for the bridging isonitrile ligands.
________________________
¹As*** = As(C₆H₄OMe-p)₃

year: 2002

title: Oxidative Decolouring of Bloodmeal Using Peracetic Acid

authors: Hicks, Talia

subjects: Bloodmeal

abstract: Bloodmeal is an ancillary product of the agricultural industry, containing 80 – 100 % protein, and has been used to create a bio-based plastic called Novatein Thermoplastic Protein®, with a proprietary blend of sodium sulfite, sodium dodecyl sulfate (SDS), water and triethylene glycol (TEG). Recent investigation has shown that the colour and odour of bloodmeal based thermoplastic can be significantly improved through the pre-treatment of bloodmeal with equilibrium peracetic acid. The resulting decoloured bloodmeal (DBM) no longer relies on the addition of sodium sulfite to be processed in conventional thermoplastic equipment. The purpose of this study was to gain a comprehensive understanding of the role by which peracetic acid decolours bloodmeal and the consequences of oxidation on composition, physico-chemical properties, protein structure and interactions and final polymer mobility.
Oxidative decolouring of haem is straightforward when the haem is freely accessible or in the form of oxyhaemoglobin and most common oxidants lead to cleavage of the porphyrin ring, resulting in a loss of colour saturation. However, after extensive thermal treatment during manufacture, the haem present in bloodmeal has migrated to inaccessible hydrophobic regions of the protein aggregates or has been oxidised to the form of methaemoglobin. Literature revealed that methaemoglobin catalytically removes hydrogen peroxide, lowering decolouring efficacy. Thus, peracetic acid is required when haem is present in the form of methaemoglobin, as is found in bloodmeal. Further, it was confirmed that a minimum of 3% w/w peracetic acid, in a 3:1 ratio to bloodmeal is required to obtain adequate decolouring (> 70% whiteness based on the RGB colour space).
The role of each component in equilibrium peracetic acid was established; water and acetic acid resulted in protein swelling but were found unlikely to influence accessibility of the oxidants to the haem sites and both hydrogen peroxide and peracetic acid were consumed in oxidising reactions. Acidic conditions were found to reduce the consumption of hydrogen peroxide, possibly through the inhibition of hydroxyl radical formation, resulting in less effective decolouring. Acetic acid was observed to have a protective effect on protein recovery as well as the resulting iron content, molecular mass distribution and secondary structure of protein.
Due to the large excess of peracetic acid solution required to facilitate diffusion and subsequent decolouring, a significant quantity remains unreacted in the recovered wastewater. Unreacted peracetic acid was shown to have potential for recycling, although in its immediate state it was insufficient to decolour fresh bloodmeal.
The protein-rich decoloured bloodmeal recovered had undergone a change in secondary structure composition and was found to contain evidence of a diffusion front, consistent with the heterogeneous phase decolouring mechanism. Oxidation with peracetic acid was found to result in less β-sheet aggregation compared to hydrogen peroxide treatment, although all treatments resulted in an increase in the quantity of disordered structures. Oxidation was also found to result in a significantly lowered glass transition temperature and along with an increased enthalpy of relaxation, evidenced a large improvement in polymer chain mobility compared with untreated bloodmeal.
DBM was found to be comprised of 90 – 99% w/w protein (1 – 10% w/w salt), with a significantly higher protein solubility and a similar volume weighted molecular mass compared with untreated bloodmeal. Further, DBM was found to have a greater composition of charged and polar amino acids, along with a large reduction in lysine and small reduction in aromatic and heterocyclic amino acids. Additionally, cystine crosslinks which stabilise bloodmeal were found to be partially oxidised to cysteine sulfonate compounds and cysteic acid (cleavage of the disulfide bond). Such a reduction in the quantity of amino acids which are capable of forming covalent networks (lysine, tyrosine and cysteine) support prior evidence that DBM no longer requires sodium sulfite to produce a thermoplastic.
The influence of SDS and TEG on secondary structure and chain mobility at ambient and elevated temperatures were explored. It was found that heating DBM and DBM with SDS alone is incapable of providing sufficient energy to induce mobility and chain rearrangement. However, the addition of TEG was found to facilitate chain mobility, and beyond 55 oC significant changes to the secondary structure composition was observed, first through the formation of α-helices and finally through the aggregation of chains into β-sheets. Wide angle X-ray scattering confirmed that the changes in ordered structures composition were reversible in DBM which contained both SDS and TEG.
The ability of TEG to plasticise DBM was more thoroughly explored, and it was found that prior to heating TEG was localised into regions either plasticiser-rich or -poor, and this resulted in the presence of two glass transition temperatures. After heating, the TEG was more homogeneously distributed, which resulted in the presence of one broad glass transition region.

text: Oxidative Decolouring of Bloodmeal Using Peracetic Acid Bloodmeal is an ancillary product of the agricultural industry, containing 80 – 100 % protein, and has been used to create a bio-based plastic called Novatein Thermoplastic Protein®, with a proprietary blend of sodium sulfite, sodium dodecyl sulfate (SDS), water and triethylene glycol (TEG). Recent investigation has shown that the colour and odour of bloodmeal based thermoplastic can be significantly improved through the pre-treatment of bloodmeal with equilibrium peracetic acid. The resulting decoloured bloodmeal (DBM) no longer relies on the addition of sodium sulfite to be processed in conventional thermoplastic equipment. The purpose of this study was to gain a comprehensive understanding of the role by which peracetic acid decolours bloodmeal and the consequences of oxidation on composition, physico-chemical properties, protein structure and interactions and final polymer mobility.
Oxidative decolouring of haem is straightforward when the haem is freely accessible or in the form of oxyhaemoglobin and most common oxidants lead to cleavage of the porphyrin ring, resulting in a loss of colour saturation. However, after extensive thermal treatment during manufacture, the haem present in bloodmeal has migrated to inaccessible hydrophobic regions of the protein aggregates or has been oxidised to the form of methaemoglobin. Literature revealed that methaemoglobin catalytically removes hydrogen peroxide, lowering decolouring efficacy. Thus, peracetic acid is required when haem is present in the form of methaemoglobin, as is found in bloodmeal. Further, it was confirmed that a minimum of 3% w/w peracetic acid, in a 3:1 ratio to bloodmeal is required to obtain adequate decolouring (> 70% whiteness based on the RGB colour space).
The role of each component in equilibrium peracetic acid was established; water and acetic acid resulted in protein swelling but were found unlikely to influence accessibility of the oxidants to the haem sites and both hydrogen peroxide and peracetic acid were consumed in oxidising reactions. Acidic conditions were found to reduce the consumption of hydrogen peroxide, possibly through the inhibition of hydroxyl radical formation, resulting in less effective decolouring. Acetic acid was observed to have a protective effect on protein recovery as well as the resulting iron content, molecular mass distribution and secondary structure of protein.
Due to the large excess of peracetic acid solution required to facilitate diffusion and subsequent decolouring, a significant quantity remains unreacted in the recovered wastewater. Unreacted peracetic acid was shown to have potential for recycling, although in its immediate state it was insufficient to decolour fresh bloodmeal.
The protein-rich decoloured bloodmeal recovered had undergone a change in secondary structure composition and was found to contain evidence of a diffusion front, consistent with the heterogeneous phase decolouring mechanism. Oxidation with peracetic acid was found to result in less β-sheet aggregation compared to hydrogen peroxide treatment, although all treatments resulted in an increase in the quantity of disordered structures. Oxidation was also found to result in a significantly lowered glass transition temperature and along with an increased enthalpy of relaxation, evidenced a large improvement in polymer chain mobility compared with untreated bloodmeal.
DBM was found to be comprised of 90 – 99% w/w protein (1 – 10% w/w salt), with a significantly higher protein solubility and a similar volume weighted molecular mass compared with untreated bloodmeal. Further, DBM was found to have a greater composition of charged and polar amino acids, along with a large reduction in lysine and small reduction in aromatic and heterocyclic amino acids. Additionally, cystine crosslinks which stabilise bloodmeal were found to be partially oxidised to cysteine sulfonate compounds and cysteic acid (cleavage of the disulfide bond). Such a reduction in the quantity of amino acids which are capable of forming covalent networks (lysine, tyrosine and cysteine) support prior evidence that DBM no longer requires sodium sulfite to produce a thermoplastic.
The influence of SDS and TEG on secondary structure and chain mobility at ambient and elevated temperatures were explored. It was found that heating DBM and DBM with SDS alone is incapable of providing sufficient energy to induce mobility and chain rearrangement. However, the addition of TEG was found to facilitate chain mobility, and beyond 55 oC significant changes to the secondary structure composition was observed, first through the formation of α-helices and finally through the aggregation of chains into β-sheets. Wide angle X-ray scattering confirmed that the changes in ordered structures composition were reversible in DBM which contained both SDS and TEG.
The ability of TEG to plasticise DBM was more thoroughly explored, and it was found that prior to heating TEG was localised into regions either plasticiser-rich or -poor, and this resulted in the presence of two glass transition temperatures. After heating, the TEG was more homogeneously distributed, which resulted in the presence of one broad glass transition region.

year: 2015

title: Behind the label: Complexities of identifying Māori whānau in an away from home hospital transfer

authors: Masters-Awatere, Bridgette

subjects: Māori whānau

abstract: This paper highlights two methodological issues that arose for a group of Māori researchers during the first few months of a Māori CoRE funded project. The issues were in relation to defining 1) the evolving construction of Māori whānau in New Zealand, and 2) an away from home hospital transfer. Through the process of reflexive practice about our knowledge constructs the research team highlight some of the complexities that we as indigenous researchers had to navigate when working within a cultural context. We describe the details of the Hospital Transfers project and reflect on the learning experienced during the pilot interview phase of a three year project.

text: Behind the label: Complexities of identifying Māori whānau in an away from home hospital transfer This paper highlights two methodological issues that arose for a group of Māori researchers during the first few months of a Māori CoRE funded project. The issues were in relation to defining 1) the evolving construction of Māori whānau in New Zealand, and 2) an away from home hospital transfer. Through the process of reflexive practice about our knowledge constructs the research team highlight some of the complexities that we as indigenous researchers had to navigate when working within a cultural context. We describe the details of the Hospital Transfers project and reflect on the learning experienced during the pilot interview phase of a three year project.

year: 2017