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1.4 CHEMICAL SCIENCES
A series of ruthenium polypyridyl complexes were studied using UV/Vis absorption and luminescence spectroscopy as well as luminescence lifetime determination by time correlated single photon counting (TCSPC). The complexes were characterised with regard to the variation in the electronic band-gap as a result of the sequential variation of the auxiliary ligand 2,2’-bipyridine (bpy), 1,10-phenanthroline (phen) and 2,2’-biquinoline (biq) ligands while the main ligand remained constant for three different main ligand types. Luminescence yields were calculated and correlated with structural and electronic variation. It was found that both the absorption and emission characteristics could be tailored through the systematic variation of the electron affinity of the individual auxiliary ligand. This was shown to be the case regardless of the functional group at the end of the main ligand. Stokes shift and Raman spectroscopy was employed as a means to gauge the effect of ligand change on the conjugation and vibrational characteristics of the complexes. Luminescence yield and lifetimes were also shown to be well-defined with regards to systematic structure variations. The well-defined trends established elucidate the effect which variation of auxiliary ligands has on the electronic characteristics of the ruthenium polypyridyl systems. These well-defined relationships can potentially be extended to optimise luminescence yield and lifetimes and therefore suitability of such compounds for the application in for example photodynamic therapy.
O'Neill, L., Perdisatt, L., O'Connor, C. The influence of auxiliary ligands on the photophysical characteristics of a series of ruthenium (II) polypyridyl complexes. Journal of physical chemistry Oct. 2012.