Novel polyoxometalate-templated, 3-D supramolecular networks based on lanthanide dimers: Synthesis, structure, and fluorescent properties of [Ln(2)(DNBA)(4)(DMF)(8)][Mo6O19] (DNBA=3,5-dinitrobenzoate)

The spherical Lindquist type polyoxometalate, Mo6O192-, has been used as a noncoordinating anionic template for the construction of novel three-dimensional lanthanide-aromatic monocarboxylate dimer supramolecular networks [Ln(2)(DNBA)(4)(DMF)(8)][Mo6O19] (Ln = La 1, Ce 2, and Eu 3, DNBA = 3,5-dinitrobenzoate, DMF = dimethylformamide). The title compounds are characterized by elemental analyses, IR, and single-crystal X-ray diffractions. X-ray diffraction experiments reveal that two Ln(III) ions are bridged by four 3,5-dinitrobenzoate anions as asymmetrically bridging ligands, leading to dimeric cores, [Ln(2)(DNBA)(4)(DMF)(8)](2+); [Ln(2)(DNBA)(4)(DMF)(8)](2+) groups are joined together by pi-pi stacking interactions between the aromatic groups to form a two-dimensional grid-like network; the 2-D supramolecular layers are further extended into 3-D supramolecular networks with 1-D box-like channels by hydrogen-bonding interactions, in which hexamolybdate polyanions reside. The compounds represent the first examples of 3-D carboxylate-bridged lanthanide dimer supramolecular "host" networks formed by pi-pi stacking and hydrogen-bonding interactions encapsulating noncoordinating "guest" polyoxoanion species. The fluorescent activity of compound 3 is reported.

Computer simulation for effect of Pr(III) on Ca(II) speciation in human interstitial fluid

A multiphase model of metal ion speciation in human interstitial fluid was constructed and the effect of Pr(III) on Ca(II) speciation was studied. Results show that free Ca2+, [Ca(HCO3)], and [Ca(Lac)] are the main species of Ca(II). Because of the competition of Pr(III) for ligands with Ca(II), the percentages of free Ca2+, [Ca(Lac)], and [Ca(His)(Thr)H-3] increase gradually and the percentages of CaHPO4(aq) and [Ca(Cit)(His)H-2] decrease gradually with the increase in the total concentration of Pr(III). However, the percentages of [Ca(HCO3)] and CaCO3(aq) first increase and then begin to decrease when the total concentration of Pr(III) exceeds 6.070 x 10(-4) M.

STUDIES ON THE COORDINATION OF TB(III) AND CA(III) WITH AMINO-ACID UNDER THE PHYSIOLOGICAL CONDITION

Tb(Ca)-glycine, Tb(Ca)-alanine, Tb(Ca)-glycine-alanine systems were studied by potentiometry (37%, I = 0.15 mol/L NaCl). The stability constants of complexes and distribution of species in ternary system were obtained. The results show Ca<Tb for the stability of binary complexes, Ca>Tb for the ternary complexes. The species convert each other with changing pH values.

New progress in R&D of lower olefin synthesis

This paper gives a brief review of R&D researches for light olefin synthesis directly and indirectly from synthesis gas in the Dalian Institute of Chemical Physics (DICP). The first pilot plant test was on methanol to olefin (MTO) reaction and was finished in 1993, which was based on ZSM-5-type catalyst and fixed bed reaction. In the meantime, a new indirect method designated as SDTO (syngas via dimethylether to olefin) was proposed. In this process, metal-acid bifunctional catalyst was applied for synthesis gas to dimethylether(DME) reaction, and modified SAPO-34 catalyst that was synthesized by a new low-cost method with optimal crystal size was used to convert DME to light olefin on a fluidized bed reactor. The pilot plant test on SDTO was performed and finished in 1995. Evaluation of the pilot plant data showed that 190-200 g of DME were yielded by single-pass for each standard cubic meter of synthesis gas. For the second reaction, 1.880 tons of DME or 2.615 tons of methanol produced 1 ton of light olefins, which constitutes of 0.533 ton of ethylene, 0.349 ton of propylene and 0.118 ton of butene. DICP also paid some attention on direct conversion of synthesis gas to light olefins. A semi-pilot plant test (catalyst 1.8 1) was finished in 1995 with a CO conversion > 70% and a C(2)(=)-C(4)(=) olefin selectivity 71-74% in 1000 h. (C) 2000 Published by Elsevier Science B.V. All rights reserved.