Strategy for Achieving Long-Wavelength Near-Infrared Luminescence of Diimineplatinum(II) Complexes.

Although many strategies have been used to help design effective near-infrared (NIR) luminescent materials, it is still a huge challenge to realize long-wavelength NIR luminescence of diimineplatinum(II) complexes in the solid state. Herein, we have successfully achieved long-wavelength NIR luminescence of a family of diimineplatinum(II) complexes based on a new strategy that combines a one-dimensional (1D) "Pt wire" structure with the electronic effect of the substituent. The structures of six solvated diimineplatinum(II) complexes based on 4,4-dichloro-2,2'-bipyridine or 4,4-dibromo-2,2'-bipyridine and 4-substituted phenylacetylene ligands have been determined, namely, 1·1/2toluene, 2·1/2THF, 3·1/8toluene, 4·1/2THF, 5·1/8CH2Cl2, and 6·1/4toluene. All of them crystallize in the monoclinic space group C2/c or C2/m and stack in the 1D "Pt wire" structure. In the solid state, six complexes exhibited unusual long-wavelength metal-metal-to-ligand charge-transfer luminescence that peaked at 984, 1044, 972, 990, 1022, and 935 nm, respectively. Interestingly, 2·1/2THF has the shortest Pt···Pt distance and the longest emission wavelength among the six complexes. As far as we know, the luminescence of 2·1/2THF at 1044 nm is the longest emission wavelength among known diimineplatinum(II) complexes. Systematic studies revealed that good molecular planarity, suitable substituent position, weak hydrogen-bond-forming ability of the substituents, appropriate molecular bending, and weakening of the interaction between solvated molecules and platinum molecules are conducive to the construction of a 1D "Pt wire" structure of the diimineplatinum(II) complex. Furthermore, the emission energy of the complex is mainly determined by the strength of the Pt-Pt interaction and electronic effect of the substituent.

Lithium uptake in fixed-pH solution by ion sieves.

In this study, Li(+) uptake by ion sieves was studied in a fixed-pH aqueous phase using a pH 8.0 buffer solution of ammonia/ammonium chloride. Two different spinel-type manganese oxide ion sieves were used to investigate the effect of intrinsic properties of ion sieves on Li(+) uptake. The effect of ionic strength was also considered for potential recovery of lithium from seawater and brine. The results of Li(+) uptake indicated that the sorption isotherms fit the Langmuir model well. The uptake was found to obey a pseudo-second-order rate. The thermodynamic parameters, DeltaG(0), DeltaH(0), and DeltaS(0), were calculated, and the results indicated that the Li(+) uptake by both ion sieves was endothermic. The influence of ionic strength was mainly found on the kinetics of Li(+) uptake. Moreover, the global reaction rate is probably controlled by both intraparticle diffusion and boundary layer diffusion, and the extent of control is greater for intraparticle diffusion than for boundary layer diffusion for Sieve-1; the reverse is for Sieve-2. Finally, Sieve-2, with high H content and small grain size, was proposed as a more suitable absorbent for recovery of lithium from seawater or brine.