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Ruthenium (II) polyaza-cavity complexes as structural and photochemical probes of electron transfer reactivity

Yearwood, G.D. (1992). Ruthenium (II) polyaza-cavity complexes as structural and photochemical probes of electron transfer reactivity. (Unpublished Doctoral thesis, City, University of London)

Abstract

A ruthenium(I I) bis (triflate) (CTf) is used to synthesise polyaza-cavity ruthenium species. Ligands, formally derived -from phenanthroline are coordinated to give mixed ligand complexes. Isolated as hexafluorophosphate salts, these complexes are characterised by elemental analysis, proton N.M.R., infra-red, FAB-mass spectrometry and uv/visible absorption spectroscopy. In an attempt to investigate the tuning of the excited state potential of these complexes, luminescence photochemical data are presented. Results for the mononuclear metallo-complexes indicate substituents to tris (1,10- mhenanthroline) coordination spheres merely alter non-radiative decay rates. Tuning of the excited state is only observed upon alteration of the ligator's magnitude of d level splitting.

Dinuclear complexes are shown to possess exciting characteristics required for tailored excited state species.

Proton N.M.R. is used to illustrate the presence of diastereomers for the complex, tetrakis (1,10-phenanthroline) [ -3,6-bis (2'-pyridyl)-1,2,4,5-tetrazine] diruthenium(II) tetrakis (hexafluorophosphate), C28. Dramatic solvent sensitivity is also demonstrated by the luminescent C28.

Distance dependence of electron transfer is investigated by derivatisation of sperm whale myoglobin with polyaza-cavity ruthenium complexes.

Analysis of the conjugate obtained with bis (1,10-phenanthroline) [4-(p -chlorosulphonyl) pheny1-1,10-phenanthroline] rutheniurn (II) , C27, gives the through space electron transfer rate, as 3.0x10* s~1. Assuming the distance between the rutheniurn (II) and iron (III) centres to be 25(+2 A) , the coupling coefficient,β, is found to be between 0.8 and 1.0. This was lower than expected for a protein matrix, suggesting a coupling enhancement effect.

A new metallo-protein is prepared by affinity labelling of chymotrypsin with a ruthenated L-phenylalanine chloromethylketone derivative, C24. Perturbation of the semi-synthetic systems excited state is tentatively ascribed to the presence of disulphide bonds in the inner—sphere.

Milestones in the analysis of long-distance electron transfer are reviewed. Also presented are pertinent considerations regarding luminescence observed at rutheniurn (II) centres.

Publication Type: Thesis (Doctoral)
Subjects: Q Science > QD Chemistry
Departments: School of Science & Technology
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