Chelates phosphorescence

Sanz-Medel / Diaz-Garcia 1994 oxygen via RTP phosphorescence quenching of ferrone chelates... 

Just as with nondoped red fluorescent dyes, nondoped phosphorescent iridium complexes consisting of two chelating phenyl-substituted quinazoline and one (2-pyridyl) pyrazolate or triazolate have recently been reported by Chen et al. (278-280) (Scheme 3.88) [308]. All of these complexes exhibited bright red phosphorescence with relatively short excited state lifetimes of 0.4-1.05 ps. PHOLEDs fabricated using the compounds A and B with relatively... 

Fig. 25. (A) DELFIA (Dissociation Enhanced Lanthanide Fluoro-ImmunoAssay) system. This heterogeneous immunoassay system uses a primary antibody bound to a solid support, to which a variable amount of unlabeled antigen is bound. The secondary antibody is labeled with a non-phospho-rescent lanthanide chelate, which becomes phosphorescent after dissociation from the antibody, due to the addition of an enhancement solution [which typically contains a mixture of sensitizer (typically a (1-diketonate) and micelle inducing surfactant (5). (B) Heterogeneous fluoroimmunoassay using a secondary antibody directly labeled with a phosphorescent lanthanide chelate.

Ohnesorge, W. E. Fluorescence of Metal Chelate Compounds. In D. M. Hercules, Fluorescence and Phosphorescence Analysis. New York-London-Sydney Interscience Publ. 1966. 

Sager, W.F., Filipescu, N., and Serafin, F.A. (1964) Substituent effects on intramolecular energy transfer. I. Absorption and phosphorescence spectra of rare earfli -diketone chelates. The Journal of Physical Chemistry, 69, 1092. 

Song, B., Wang, G.L., and Yuan, J.L. (2005) A new europium chelate-based phosphorescence probe specific for singlet oxygen. Chemical Communications, 3553—3555. 

Enedithiolates (dithiolenes ) were used originally together with other ligands for production of chelates of transition metals for determination by UVD. After the discovery of photophysical properties of Pt complexes of certain 1,2-enedithiolates, they were used as phosphorescence and fluorescence dual emitters for oxygen and proton detection. The analytical applications of 1,2-enedithiolates have been reviewed. ... 

It appears that dissociation of tetrakis chelates in solution to give free ligand anions (which show phosphorescence lifetimes long with respect to those of ion fluorescence) (4) is responsible for reports of the observation of both molecular phosphorescence and ion fluorescence from solutions of certain europium -diketonates, the unequal lifetimes of which led to the suggestion that energy transfer to the europium ion came from a different triplet level (or a higher triplet level) than that from which phosphorescence is observed. 

Table IV. Phosphorescence Lifetimes of Piperidinium [BFTA]4 Ln Chelates at 77°K.

The plots of log intensity vs. time of the phosphorescence of the Gd chelates were resolvable into two components the slow one dominates in EEA and the fast one dominates in (crystalline) CH3CN. In EEA, this behavior is independent of concentration over the range 10 2 to lO M. 

This enhancement of intersystem crossing by combining heavy atom and paramagnetic effects explains the relative insensitivity of the Gd phosphorescence lifetime (Table IV) to any additional heavy atom effect (as in the chelate with iodo-BTFA), or to deuteration of solvent or ligand which, by inhibiting nonradiative deactivation, usually increases the lifetime of organic phosphorescence. This insensitivity of the lifetime of the Gd chelate permits us to assign the value of ca. 3 X sec." as the intrinsic radiative rate for the triplet state for Gd BTFA chelates, and a similar value should apply for the Eu compounds. 

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