Luminescence sensing, lanthanide complexes

Gunnlaugsson, T., Harte, A.J., Leonard, J.R, and Nieuwenhuyzen, M. (2002) Delayed lanthanide luminescence sensing of aromatic carboxylates using heptadentate triamide Tb(III) cyclen complexes the recognition of salicylic acid in water. Chemical Communications, 2134-2135. 

For coordinating and sensing luminescent lanthanide ions, a luminescent ruthenium bipyridyl complex has been covalently linked to one, two or six lower rim acid-amide modified caUx[4]arene moieties in receptors 155-157. All these complexes coordinated with lanthanide ions, Nd , Eu and Tb, with the formation of adducts of variable stoichiometries. The adduct formation affected the Ru luminescence, which was strongly quenched by Nd ion, increased by the Tb ion and moderately quenched or increased by Eu ion (2004IC3965). 

The detection of DNA strands by NIR luminescent lanthanide complexes is possible through the modulation of Yb luminescence in Pd-porphyrin-containing complexes upon nucleic acid binding [48] or by the sensitivity of the intramolecular energy transfer towards the presence of DNA sensing in coumarin-rhodamine-modified ytterbium complexes [95]. 

Another problem of using lanthanide complexes as luminescent probes is their susceptibility to interferences. This diminishes the selectivity of the response to a certain analyte and impedes analytical applications in complex samples. The incorporation of LLCs in solid state matrices leads to responsive layers that can be integrated in optical devices for continuous sensing. 

Properly designed unsaturated lanthanide complexes function as anion-specific luminescent receptors for ternary complexation with certain external anions that can be detected by naked-eye methods. Thus, such a sensing techniqne nsing lanthanide complexes may have practical applications. 

The luminescence and thermal properties of lanthanide(III) complexes can be manipulated and enhanced by designing organic ligands which coordinate to lan-thanide(III) ions. In this thesis, molecular designs for the enhancement of the luminescence properties and functionalization (thermostability and temperature-sensing ability) of lanthanide complexes with LVF phosphine oxide ligands have been described. The results obtained in this study were briefly summarized as follows. 

The author wishes the strategies for molecular design of luminescent lanthanide complexes described in this thesis would have contribution to development of applications in novel organic lanthanide devices, such as organic liquid lasers, luminescent plastics, optical fibers, EL devices, and temperature-sensing devices. The photochemistry of luminescent lanthanide complexes is expected to open up frontier fields between lanthanide coordination chemistry and photo-functional materials science. 

Shinoda S, Tsukube H. Luminescent Lanthanide Complexes as Analytical Tools in Anion Sensing, pH Indication and Protein Recognition. Analyst 2011 136 431-435. 

Anion sensing using visible-emitting lanthanide probes has proven successful (Tsukube et al., 2006) and this work is now being extended to Ybm probes, particularly for the detection of thiocyanate. The latter is the principal metabolite of cyanide anion and exists in human serum, saliva, and urine. The luminescent probe is a complex of hexadentate tetrakis(2-pyridylmethyl)ethylenediamine (tpen, see fig. 119) which bears two water molecules, [Yb(tpen)(H20)2](0tf)3. In absence of anion coordination, the 980-nm luminescence is quenched, but the replacement of the water molecules with thiocyanate or other anions such as acetate, nitrate or halogenides removes the quenching, which makes the complex a responsive probe. The largest effect (a six-fold increase in luminescence) is obtained for thiocyanate, followed by acetate and nitrate (3.5-fold) and chloride (two-fold). 

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