Ruthenium polypyridyl compounds as luminescent probes for biological materials
Ryan, Eleanor M. (1991) Ruthenium polypyridyl compounds as luminescent probes for biological materials. PhD thesis, Dublin City University.
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The synthesis and characterisation of ruthenium (II)
bis-(1 ,10-phenanthroline) and bis-(2 ,2 1-bipyridyl) complexes containing amino and isothiocyanate phenanthroline and pyridine ligands are described. These complexes were
characterised using HPLC, UV/vis spectroscopy,
electrochemistry, NMR, IR, and emission spectroscopy. HPLC
was used to determine the purity of the various complexes.
Electronic spectra and electrochemical measurements indicate that most likely, the 2 ,2 '-bipyridyl
and 1 ,10-phenanthroline ligands are the emitting ligands and the amino and isothiocyanate phenanthroline and pyridine
ligands act as the spectator ligands.
These complexes were subsequently conjugated to
biological materials, including albumins, immunoglobulins and poly-L-lysine. The complexes were bound at different sites on the biomolecules, via the lysine residues, the
carbohydrate moieties and via the tyrosine residues.
The effect of conjugation on the spectroscopic
properties of the complexes was examined. The absorption
spectra were found to exhibit changes in the MLCT band with
the absorption wavelength maximum experiencing slight red
shifts together with general band broadening effects. The
emission decay behaviour was also investigated. The unbound
complexes were found to exhibit single exponential decay
behaviour and the bound complexes exhibited essentially
double exponential behaviour. From the double exponential
decay fits, the first short-lived species was suggested to be a quenched bound species whilst the second species probably arises from a bound species which is considerably protected from the effects of quenching molecules.
The synthesis and characterisation of a number of
bis-(1 ,10-phenanthroline) (phen), and bis-(4,4'-dimethyl-
2, 2'-bipyridyl) (dmbpy), ruthenium (II) complexes containing a series of pyridyltriazole ligands are described. The ruthenium ion may bind via the Nl'/ N 2 ' or n4' of the triazole ring. The most favourable coordination mode being dependent on the position of a substituent on the triazole ring. Coordination isomers were obtained and separated by semi-preparative HPLC methods. The electrochemical results suggest that the phen and dmbpy ligands are the emitting ligands and that the pyridyltriazole ligands are the spectator ligands.
The acid-base chemistry of those pyridyltriazole
complexes which can undergo protonation / deprotonation
reactions was investigated and the results substantiated the
coordination modes proposed using NMR data for the
complexes. The ground state pKa values show that there is
a strong a-donating effect from the triazole ring to the
ruthenium ion. Also, the excited state pKa* values are
lower than the ground state pKa values which indicates that
the pyridyltriazole ligands do not participate in the
emission process. This study completes investigations which
were initially conducted on the 2 ,2 '-bipyridyl analogues.
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