http://bura.brunel.ac.uk/handle/2438/228 The Wolfson Centre for Materials Processing was established in 1987 as a focus for materials research in Brunel University. Since its inception, the research in the Centre has been based on the development of extrusion and injection-moulding technologies relating to polymer compound formulation, process-induced structuring, nano-composite processing and the processing of metals, ceramics, soft solids and natural materials. 2026-03-26T08:30:04Z http://bura.brunel.ac.uk/handle/2438/29961 Title: Protoporphyrin IX iron(II) revisited. An overview of the Mössbauer spectroscopic parameters of low-spin porphyrin iron(II) complexes Authors: Silver, J; den Engelsen, D; al-Jaff, G; Taies, JA; Wilson, MT; Fern, GR Abstract: Mössbauer parameters of low-spin six-coordinate [Fe(II)(Por)L2] complexes (where Por is a synthetic porphyrin; L is a nitrogenous aliphatic, an aromatic base or a heterocyclic ligand, a P-bonding ligand, CO or CN) and low-spin [Fe(Por)LX] complexes (where L and X are different ligands) are reported. A known point charge calculation approach was extended to investigate how the axial ligands and the four porphyrinato-N atoms generate the observed quadrupole splittings (ΔEQ) for the complexes. Partial quadrupole splitting (p.q.s.) and partial chemical shifts (p.c.s.) values were derived for all the axial ligands, and porphyrins reported in the literature. The values for each porphyrin are different emphasising the importance/uniqueness of the [Fe(PPIX)] moiety, (which is ubiquitous in nature). This new analysis enabled the construction of figures relating p.c.s and p.q.s values. The relationships presented in the figures indicates that strong field ligands such as CO can, and do change the sign of the electric field gradient in the [Fe(II)(Por)L2] complexes. The limiting p.q.s. value a ligand can have and still form a six-coordinate low-spin [Fe(II)(Por)L2] complex is established. It is shown that the control the porphyrin ligands exert on the low-spin Fe(II) atom limits its bonding to a defined range of axial ligands; outside this range the spin state of the iron is unstable and five-coordinate high-spin complexes are favoured. Amongst many conclusions, it was found that oxygen cannot form a stable low-spin [Fe(II)(Por)L(O2)] complex and that oxy-haemoglobin is best described as an [Fe(III)(Por)L(O2−)] complex, the iron is ferric bound to the superoxide molecule. Description: Availability of data and materials: No datasets were generated or analysed during the current study. 2024-10-10T00:00:00Z http://bura.brunel.ac.uk/handle/2438/25392 Title: Reduction of the structural iron in montmorillonite by electron transfer from catechol and its derivatives Authors: Hassen, JH; Silver, J Abstract: Copyright © The Authors 2021. The structural Fe(III) in montmorillonite (MMT) clay has been reduced using catechol and its derivatives. It was found that the reduction process is pH-dependent and also depends on the ring substituents. If the catecholic ring has electron-donating substituents, reduction happens at high pH; if the catecholic ring has electron-withdrawing substituents, no reduction occurs. The process involves electron transfer from the hydroxy groups on the compounds to the active site at the iron atoms within the MMT lattice. This site acts as an electron acceptor (Lewis acid). Heat treatment of the reduced sample at 100-300 oC showed an enhancement of the Fe2+/Fe3+ ratio, which is attributed to an increase in the proportion of radicalic formation induced by dehydration. The MMT sample was added to the solutions of the catecholic compound and the slurries were stirred for 24 hours in order to reach equilibrium, then filtered, washed, and air-dried. The reactions were monitored using Mössbauer spectroscopy, x-ray powder diffraction, differential thermal analysis, electron spin resonance, infrared, and total surface area determination. 2021-11-30T00:00:00Z http://bura.brunel.ac.uk/handle/2438/25390 Title: Firing-activated interaction of montmorillonite with tin(Iv) and copper(ii) phthalocyanine dyes Authors: Hassen, JH; Silver, J Abstract: Copyright © The Authors 2021. The adsorption of phthalocyanines Pcs complexes onto montmorillonite MMT clay differs from that of the other complexes like porphyrins, in that the adsorption process can be completed only after firing treatment of the solid mixture. The MMT particles act as a complex-hosting matrix, and the actual adsorption process of the complexes onto the MMT occurs only after firing. This firing treatment generates different colors on firing the solid mixtures to different temperatures. When tin(IV) phthalocyanine dichloride Sn(IV)PcCl2 complex is adsorbed onto the MMT, the chloride ligands are replaced by oxygen, and the complex is more protected from decomposition due to firing and solution effects. Both complexes, diamagnetic Sn(IV)PcCl2 and the paramagnetic Cu(II)Pc are found in a free radical state on the MMT surface or intercalated in the interlayer after firing, produced by electron transfer from the complexes to the MMT. It was found by X-ray powder diffraction investigation that firing treatment of the air-dried metal Pc-MMT samples induces intercalation of the complexes in the MMT interlayer. 2021-10-01T00:00:00Z http://bura.brunel.ac.uk/handle/2438/25388 Title: Studies on the binding of CO to low-spin [Fe(II)(Por)L2] complexes: an aid to understanding the binding of CO to haemoglobin and myoglobin Authors: Silver, J; al-Jaff, G; Taies AJ; Wilson, MT; den Engelsen, D; Fern, GR; Ireland, TG Abstract: Copyright © The Author(s) 2022. The visible and Mössbauer spectra of [Fe(II)(Por)L2] and [Fe(II)(Por)L(CO)] complexes (where Por = protoporphyrin IX (PPIX) or tetra(p-sulfophenyl)porphyrin (TPPS) and L = an aliphatic or aromatic nitrogenous base) are reported and discussed. The results are compared to those of previously reported [Fe(II)(Por)L(CO)] complexes (where Por = PPIX, TPPS, PMXPP, TPP, OMTBP and OEP; L = a nitrogenous aromatic ligand) and HbCO (where Hb = haemoglobin) and MyCO (where My = myoglobin). A new approach, to extracting information from the Mössbauer parameters has been developed by plotting those of the [Fe(II)(Por)L2] complexes against those of [Fe(II)(Por)L(CO)] complexes for the same ligands, has yielded a series of trend lines that show a significant dependence on both the nature of the porphyrin and also of the nitrogenous ligand. Different trend lines were found for aromatic nitrogenous ligands to aliphatic nitrogenous ligands showing that the porphyrins could donate different amounts of charge to the Fe(II) cations as the L ligand changed, and hence, they display electron sink properties. From the plots, it was shown that haemoglobin and myoglobin both bind CO very strongly compared to the model complexes studied herein. Using the reported structural and Mössbauer data for the [Fe(II)(Por)L2] and [Fe(II)(Por)L(CO)] complexes, it proved possible and instructive to plot the Mössbauer parameters against a number of the bond lengths around the Fe(II) cations. The interpretation of the resulting trend lines both supported and facilitated the extension of our findings enabling further understanding of the geometry of the bonding in CO haemoglobin and CO myoglobin. 2022-12-07T00:00:00Z