1,721,072 research outputs found
NIR-emissive Erbium Quinolinolate Complexes
No full textStudies addressed to a deep understanding of the structure/property relationship on the near infrared (NIR)-emissive erbium-quinolinolate complexes, which are of interest for low-cost photonic systems, are reviewed. The role of the 8-quinolinolate ligand (Q), which studies also as sensitizer to overcome the weak absorptivity of lanthanide ion, is discussed. Synthetic and structural aspects are reported to revise the old assumption that these complexes are analogous in structure to AlQ3 and to point out the specificity of the lanthanide coordination chemistry. In fact depending on reaction conditions, species with high coordination numbers and differing for nuclearity and stoichiometry have been isolated and fully characterized. In some instances it has been shown that coordinated water molecules directly bounded to the emitting erbium ion definitely represent the most effective quenchers for the luminescence at 1.5μm. Additionally, the combined optical and structural investigation of water-free Er-quinolinolate complexes, allows one to conclude that the C-H groups sitting in the Er3+ inner coordination sphere represent a very severe limit to the near-infrared emission yield. Implementation of structural/spectroscopic data into a theoretical model based on Förster's energy transfer resonant theory provides a comprehensive analysis of the near infrared emission quenching in erbium complexes useful to predict the quenching effects in luminescent lanthanide-complexes from the measurements of the vibrational absorption spectrum of the compound, the lanthanide radiative lifetime, and the minimum distance between the emitting ion and the quenchers. On that basis, in order to significantly improve the near-infrared emission yield, ligands which do not bear NH, CH or OH groups at a distance shorter than 7-8Å from the emitting ion are required. At the same time high sensitization efficiency of near-infrared emission and population saturation of trivalent erbium is achieved in these complexes, photoexcited into the absorption band of the quinolinolate sensitizer. It is concluded that a fully halogenated quinolinolate ligand can be an optimal candidate to improve the luminescent properties of erbium complexes. © 2011 Elsevier B.V
“Molecular materials based on transition-metal complexes with dichalcogenolene and quinolinolate ligands”
No full textFrom trash to resource: a green approach to noble-metals dissolution and recovery
No full textA process based on the lixiviant properties of organic mixtures of dihalogen/S,S-ligands, N,N′-dimethyl-perhydrodiazepine-2,3-dithione (Me2dazdt) and tetraalkylthiuramdisulphide (Et4TDS) in the presence of diiodine, for gold recovery from the non-ferrous metal fraction of real shredded waste electric and electronic equipment (WEEE), is presented here. Selective dissolution of metals is achieved through a sequence of three steps where the oxidation of different kinds of metals is achieved by using: (1) refluxing water solutions of HCl 1:5 under Ar atmosphere (Sn, Zn, etc.); (2) water solutions of NH3/(NH4)2SO4 mixtures in the presence of H2O2 on the resting sample(Cu, Ag); and (3) acetone solutions of Me2dazdt or Et4TDS/I2 mixtures on the final residue (Au). Each step is followed by a further treatment for: (1) metal recovery, in the case of Au, Cu, Ag; and (2) inertization, in the case of heavy metals. As a whole, the process is very promising for effective recovery of gold and other valuable noble-metals and for using non harmful reagents in mild conditions
Chameleon behaviour of iodine in recovering Noble-Metals from WEEE: towards sustainability and “zero” waste
No full textAn effective and sustainable method for the selective leaching of metals from the non-ferrous metal fraction of Waste Electric and Electronic Equipment (WEEE) is described here. This method consists of a sequence of steps which involve the selective leaching of the different metals from the shredded sample by using environmentally friendly lixiviants in water. In particular: (1) a refluxing citric acid (3 M) solution which dissolves Sn, Zn, Pb, Ni, and other base metals; (2) NH3 in combination with an IO3−/I− mixture which allows one to oxidize Cu and Ag, and to separate them by selective AgI precipitation; (3) an I−/I2 mixture (5.3 : 1 molar ratio) which is capable of leaching quantitatively Au metal from the solid residue. Each step is followed by a further treatment for: (i) high-rate metal and reagent recovery, in the case of NMs; (ii) inertization, in the case of heavy metals. The “chameleon” behaviour of iodine, which shows versatile redox/complexing/precipitating capabilities, allows one to achieve, on the one hand, a selective noble-metal (NM) leaching and, on the other hand, a simple and effective reagent and metal recovery. The comparison of the above described method with a similarly effective one previously patented by some of the same authors, allows one to point out that a significant improvement in sustainability is achieved in terms of lixiviant employment, which is of low cost, easily available and recyclable, and able to work in water solutions, while maintaining or improving its environmentally friendly character
Croconato-containing M(III) (M = Cr, Er) complexes as suitable building blocks for multifunctional materials
No full textSynthesis, Crystal Structure and Physical Properties of TTF(ET)/M(dithiocroconate)2 (M= Cu, Au) CT-salts
No full textSynthesis, X-Ray Characterization and Physical Properties of novel CT-Salts based on [M(croconate)3]3- Chiral Anions
No full textMultifunctional Molecular Materials Based on [Mn(III)]2 SMM and Conducting Metal Dithiolene Complexes
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