Metal-containing compounds, luminescence

The popularity of the BCD can be attributed to the high sensitivity to organohalogen compounds, which include many compounds of environmental interest, including polychlorinated biphenyls and pesticides. It is the least selective of the so-called selective detectors but has the highest sensitivity of any contemporary detector. The NPD or thermionic ionization or emission detector is a modified FID in which a constant supply of an alkali metal salt, such as rubidium chloride, is introduced into the flame. It is a detector of choice for analysis of organophosphorus pesticides and pharmaceuticals. The FPD detects specific luminescent emission originating from various excited state species produced in a flame by sulfur- and phosphorus-containing compounds. 

The control of pH in a solution containing a luminescent analyte is also of great importance for sensitive and reliable analysis. For aromatic compounds with acidic or basic substituents, excitation and emission wavelengths of the ionized and free forms are likely to differ. In the case of fluorescence from metal chelates, the pH must be controlled to ensure that the conditional stability constant for the complex is optimal for the particular analytical situation. 

Having investigated the electrochemical behavior of ZnSe, and in view of the well-known blue luminescence of the compound, the previous authors extended their work to study electroluminescence from I-doped n-ZnSe crystals under anodic polarization in aqueous media containing metal ions such as Cu(II) and Sn(II) [123]. 

Blue luminescence of zinc complexes of pyridyl-containing complexes is an area of current interest.277 Design of blue luminescent materials is of relevance to display applications, as blue-light-emitting diodes, and to this end Che examined solution luminescence of zinc pyridylamine complexes.73,278 Che and co-workers studied the complex Zn40(7-azaindoyl)6 which has a blue emission at 433 nm in the solid state.279,280 In an attempt to improve on stability Wang et al. examined compounds with neutral 7-azaindole and an A-functionalized pyridyl derivative.281 In contrast with other metal complexes of the neutral 7-azaindole (32), Zn(7-azaindole)2(OAc)2 is a blue luminescent compound and a A-(2-pyridyl) 2-azaindole (33) and its complexes were also... 

The delayed light emission as observed from the Bolonian stone is now classified as phosphorescence. We know now that these stones contain barium sulfate with traces of bismuth and manganese, and that the corresponding reducing process concerns the transformation of sulfate into sulfur. It is now well known that alkaline earth metal sulfates emit phosphorescence that strongly increases when traces of heavy metals are present. The so-called inorganic multi-component compounds phosphor and crystallophosphor are in fact polycrystalline substances containing traces of some ionic activators of luminescence. 

The stability of the polypyridyl rhenium(I) compounds mentioned above stimulated applications of this coordination chemistry. Thus, new heterotopic bis(calix[4]arene)rhenium(I) bipyridyl receptor molecules have been prepared and shown to bind a variety of anions at the upper rim and alkali metal cations at the lower rim. A cyclodextrin dimer, which was obtained by connecting two permethylated /3-cyclodextrins with a bipy ligand, was used for the preparation of a luminescent rhenium(I) complex. The system is discussed as a model conipound to study the energy transfer between active metal centers and a bound ditopic substrate. The fluorescence behavior of rhenium(I) complexes containing functionalized bipy ligands has been applied for the recognition of glucose. ... 

Fluorescent redox switches based on compounds with electron acceptors and fluorophores have been also reported. For instance, by making use of the quinone/ hydroquinone redox couple a redox-responsive fluorescence switch can be established with molecule 19 containing a ruthenium tris(bpy) (bpy = 2,2 -bipyridine) complex.29 Within molecule 19, the excited state of the ruthenium center, that is, the triplet metal-to-ligand charge transfer (MLCT) state, is effectively quenched by electron transfer to the quinone group. When the quinone is reduced to the hydroquinone either chemically or electrochemically, luminescence is emitted from the ruthenium center in molecule 19. Similarly, molecule 20, a ruthenium (II) complex withhydroquinone-functionalized 2,2 6, 2"-terpyridine (tpy) and (4 -phenylethynyl-2,2 6, 2"- terpyridine) as ligands, also works as a redox fluorescence switch.30... 

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