| Abstract
| - Ru(phen)n(bps)3-n2n-4(n = 0−3) complexes were prepared to probe theinteractions with cationic, anionic, and neutral surfactants.Premicellar aggregates formed byRu(bps)34- with DTAB exhibita 22-fold decrease in emission intensity and marked changes in theabsorption spectrum. Complexes possessing bps ligands do notexhibit significant changes in their spectral properties upon additionof micelles, compared to those observed forRu(phen)32+, indicative of their greaterhydrophilicity.
- TheRu(phen)n(bps)3-n2n-4(n = 0−3) complexes (phen = 1,10-phenanthroline,bps = disulfonated 4,7-diphenyl-1,10-phenanthroline) were prepared to probe the hydrophobic andelectrostatic interactions with cationic DTAB(n-dodecyltrimethylammonium bromide), anionic SDS (sodiumdodecyl sulfate), and neutral C12E8 (n-dodecyloctaoxyethylene glycol monoether) surfactants. The measuredemission maxima and lifetimes are consistentwith the population of the Ru → phen MLCT (metal-to-ligand chargetransfer) excited state in Ru(phen)32+andthe lower-lying Ru → bps MLCT excited state inRu(phen)n(bps)3-n2n-4(n = 0−2). Premicellar aggregates withoppositely charged surfactants lead to decreased overall emissionintensity for all complexes. In particular,aggregates formed byRu(bps)34- with DTAB exhibita 22-fold decrease in emission intensity and markedchangesin the electronic absorption spectrum, with a concomitant appearance ofa shorter lifetime component. Thephotophysical characteristics of the premicellar adduct can beexplained by changes in the relative energies of theemissive 3MLCT state and the 3ππ*state of the bps ligands, such that more effective deactivation of the3MLCTthrough the 3ππ* state is possible. The resultsshow that complexes possessing at least one bps ligand donotexhibit significant changes in their spectral properties upon additionof DTAB, C12E8, and SDS micelles, comparedto those observed for Ru(phen)32+,interpreted as reduced interaction between bps-containing complexes andthemicellized surfactants. The interactions (inferred from changes inspectral properties) between Ru(phen)32+andthe cationic DTAB system are greater than those ofRu(bps)2(phen)2- withthe anionic SDS surfactant, althoughboth complexes possess overall charge of equal magnitude. Theseobservations can be explained in terms of thedifferences in the hydrophilicity of the complexes.
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