Lanthanoids luminescence

Chiral recognition of A-[Co(phen)3]3+ has been observed in a modified /3-cyclodextrin.772 Chiral discrimination has also been seen in photoinduced energy transfer from luminescent chiral lanthanoid complexes773 to [Co(phen)3]3+ and between photoexcited [Ru(bpy)3]2+ and [Co(phen)3]3+ co-adsorbed on smectite clays.774 The [Co(bpy)3]3+ ion has been incorporated into clays to generate ordered assemblies and also functional catalysts. When adsorbed onto hectorite, [Co(bpy)3]3+ catalyzes the reduction of nitrobenzene to aniline.775 The ability of [Co(phen)3]3+ to bind to DNA has been intensively studied, and discussion of this feature is deferred until Section 6.1.3.1.4. 

Modification of the ligand by replacing the quinoline with a pyridine group allows the introduction of lanthanoid ions (Eu3+, Tb3+) into the cage and luminescence properties [144]. 

At present, luminescence determination methods are available for almost all elements of the periodic table (Fig. 3). Most extensively used are methods whereby fluorescent, more rarely phosphorescent, complexes of elements with organic ligands are obtained. Many methods utilize the native luminescence of lanthanoides (III), uranyl, mercury-like and other ions in crystallophosphors and complexes with inorganic and organic ligands and also chemiluminescence. 

Many lanthanoid ions have luminescent properties whieh are employed in numerous applications as sensors, in bioimaging, and as phosphors. The most conunonly used are Eu " (red), Tb (green) and Eu (blue-red depending on the environment). Holmium salts spectaculariy change eolour from pale yellow to red with appropriate irradiation. 

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