Anandan, Shanti (2012) Understanding the factors which Influence the interactions of iron (II) and iron (III) in porphyrins and the chemistry of silicon phthalocyanine. PhD thesis, University of Greenwich.

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Abstract

The work presented in this thesis involved the study of iron(II) and iron(III) porphyrins using high-pressure Mössbauer spectroscopy. Further work was aimed at the formation of a new complex between iron(III) tetraphenylporphyrin chloride [Fe(III)TPPCl] and silicon phthalocyanine di-4pyridinecarboxylic acid [Si-Pc(4PyCOO)2].

The synthesis of tetraphenylporphyrin (H2TPP) and Fe(III)TPPCl was achieved and verified using CHN analysis, UV spectrometry and ambient pressure Mössbauer spectroscopy. However the synthesis of pure Si-Pc[PyCOO]2 proved to be difficult. The intention to form a complex between Fe(III)TPPCl and Si-Pc[PyCOO]2 was not successful, despite many attempts. The reason for this was due to the nature of Si-Pc[PyCOO]2. The axial ligand [PyCOO] has higher affinity for H+ than [Fe(III)TPP]+. The difference in solubility of Fe(III)TPPCl and Si-Pc[PyCOO]2 in chloroform caused another problem in the formation of the complex due to the nature of the solvent. Chloroform is too hygroscopic and even a limited exposure to the atmosphere decomposes the Si complex.

An understanding of some of the factors that control the spin state of Fe(III)OEPCl and Fe(III)PPIXCl was made possible using high-pressure Mössbauer spectroscopy studies. Many synthetic porphyrins have been studied to model the structure and the reactions of haemoproteins. One of the reasons for this is that [PPIXFe(II/III)] (haem) is difficult to crystallise whereas Fe(TPP) and Fe(OEP)-compounds readily crystallise.

Mössbauer spectroscopy was used to study the spin state of iron(III) and its changes in 57 Fe(III)OEPCl under high-pressure conditions. This area of study is an extension of previous work on 57 Fe(III)PPIXCl using the same technique. Evidence of the nuclear interactions parameter (quadrupole splitting, ΔEQ) was established for the change in the spin state from high spin to the spin admixed S = +/- 3/2, +/- 5/2 state. Furthermore, high-pressure Mössbauer spectroscopy was shown to be a powerful technique to study this kind of spin state - "spin admixed". Examples were used from previous studies to compare the change in the spin state. 57 Fe(III)OEP[4-NH2Py]2 was also synthesised and compared with [57FePPIX[HIm]2]Cl using high pressure Mössbauer study. The Mössbauer data for these compounds when compared with a whole range of [Fe(III)Por(L)2]+ complexes provided a better understanding of the structural conformation, the orientation of ligands [parallel or perpendicular positions] in relation the Fe-N plane. The comparative study using similar substituted ligands of imidazoles demonstrated that ligands binding to the iron influence the electronic structure in relation to pressure. Probing with the nuclear interactions using Mössbauer technique explained some of the informations and factors that control the spin state in these compounds.

Item Type:	Thesis (PhD)
Additional Information:	uk.bl.ethos.571446
Uncontrolled Keywords:	organic compounds, porphyrins, Mössbauer spectroscopy,
Subjects:	Q Science > QD Chemistry
Pre-2014 Departments:	School of Science School of Science > Department of Pharmaceutical, Chemical & Environmental Sciences
Last Modified:	17 Mar 2017 16:00
URI:	http://gala.gre.ac.uk/id/eprint/9135

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