Relationships between luminescent properties and structure in β-K2SO4-type orthophosphates

The conditions of a Ce³⁺ → Tb³⁺ energy transfer have been analyzed in the Na_2+x+yCa_2(1?x?y) Ce_xTb_y(PO₄)₂ orthophosphates. Terbium green emission through uv cerium excitation is characterized by a very low yield. This result is the consequence of a sodium-rare-earth short range ordering even at low rare-earth concentrations and of lack of rigidity in the anionic sublattice.     

The cocrystal of 3‐hydroxy‐2‐naphthoic acid and 4,4′‐bipyridine

4,4′‐Bipyridine cocrystallizes with 3‐hydroxy‐2‐naphthoic acid in a 1:2 ratio to give a centrosymmetric three‐component supra­molecular adduct, namely 3‐hydroxy‐2‐naphthoic acid–4,4′‐bipyridine (2/1), C₁₁H₈O₃·0.5C₁₀H₈N₂, in which 4,4′‐bipyridine is located on an inversion center. The pyridine–carboxylic acid heterosynthon generates an infinite one‐dimensional hydrogen‐bonded chain viaπ–π inter­actions between naphthyl and 4,4′‐bipyridine groups. The one‐dimensional chains are further assembled into a three‐dimensional network by weak C—H⋯π inter­actions between pyridyl and naphthyl rings, and C—H⋯O inter­actions between 3‐hydroxy‐2‐naphthoic acid mol­ecules.     

The asymmetric synthesis of (−)-pumiliotoxin C using tandem catalysis

The potent neurotoxin (−)-pumiliotoxin C has been prepared in 8 steps starting from 2-cyclohexenone. Key steps are a tandem asymmetric conjugate addition-allylic substitution reaction and a tandem Heck-allylic substitution reaction.     

Dynamic optimization of a dead-end filtration trajectory: Non-ideal cake filtration

A control strategy aimed at minimizing energy consumption is formulated for non-ideal dead-end cake filtration with an inside-out hollow fiber ultrafiltration membrane system. The non-ideal behavior was assumed to originate from cake compression, non-linear cake resistance and a variable pump efficiency.

Constant gross power, constant flux and constant pressure filtration were considered as alternatives for the optimal operating strategy. It was found that the ratio between the initial and final total resistance determines whether a large difference between these strategies occurs. This is mainly determined by the specific cake resistance, the final state and the membrane resistance.

When there is a large difference between the operating strategies, the pump characteristics determine which suboptimal strategies are attractive. For a pump with a low head and a large capacity, constant flux filtration is nearly optimal, whereas for a pump with a large head and a small capacity optimal operation is closer to constant pressure filtration. Under the investigated conditions there was no significant difference (< 0.5%) between the constant gross power and the optimal operating strategy.     

Catalytic enantioselective synthesis of (-)-prostaglandin E1 methyl ester based on a tandem 1,4-addition-aldol reaction

Catalytic enantioselective 1,4-additions and tandem 1,4-addition-aldol reactions of dialkylzinc reagents to cyclopentene-3,5-dione monoacetals in the presence of an in situ generated Cu(OTf)(2)/chiral phosphoramidite catalyst result in highly functionalized cyclopentane building blocks with ee's up to 97%. A new synthesis of cyclopentene-3,5-dione monoacetals is presented as well as its use in a tandem 1,4-addition-aldol protocol for the catalytic asymmetric total synthesis of (-)-PGE(1) methyl ester. This synthesis represents a new approach to this class of natural products. By using only 3 mol % of an enantiomerically pure catalyst in the key step, the absolute configurations at three stereocenters of the basic structure of the PGE(1) are established at once.     

Thermal decomposition of Cu(I) phosphine complexes

The thermal decomposition of Cu(I) phosphine complexes of the general types (CuXPPh₃)₄, [CuX(PPh₃)₂] and [CuX(PPh₃)₃] was investigated.The thermal decomposition of (CuXPPh₃)₄, where X denotes Cl^–, Br^–, I^–, NO ₃ ^– and PPh₃=P(C₆H₅)₃, occurs with formation of a phosphine oxide intermediate. For the remaining complexes this intermediate was not proved in the thermal decomposition.

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Zusammenfassung Die thermische Zersetzung der Cu(I)-Phosphinkomplexe vom allgemeinen Typ (CuXPPh₃)₄ und [CuX(PPh₃)₂], wie auch [CuX(PPh₃)₃] wurde untersucht. Die thermische Zersetzung von (CuXPPh₃)₄, wobei X=Cl^–, Br^–, I^– und NO ₃ ^– bedeutet und PPh₃=P(C₆H₅)₃, verläuft unter Bildung eines Phosphinoxid Zwischenproduktes, bei den übrigen Komplexen konnte dieses im Laufe der thermischen Zersetzung nicht nachgewiesen werden.

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Résumé On a étudié la décomposition thermique des complexes phosphine-Cu(I) de formule générale (CuXPPh₃)₄, [CuX(PPh₃)₂], [CuX(PPh₃)₃]. La décomposition thermique de (CuXPPh₃)₄, où X désigne Cl^–, Br^–, I^– et NO ₃ ^– , et PPh₃=P(C₆H₅)₃, s'effectue avec formation d'un oxyde de phosphine intermédiaire; avec les autres complexes, cet intermédiaire n'a pas été mis en évidence au cours de la décomposition thermique.

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(CuXPPb₃)₄ [CuX(PPh₃)₂] [CuX(PPh₃)₃]. (CuXPPh₃)₄, X=Cl^–, Br^–, I^–, NO ₃ ^– , PPh₃=(₆₅)₃ . .

     

Preparation, characterization, and solution tailored photoluminescence of all trans poly[distyrylbenzene-b-(ethylene oxide)]s

Two linear, stereoregular, and structurally defined PPV derivatives (PPVs), poly[distyrylbenzene-b-(ethylene oxide)]s, with respective 12 and 16 of ethylene oxide repeat units in the backbone, abbreviated as DE-1 and DE-2 thereinafter, have been prepared via a modified synthetic profile. Both DE-1 and -2 were soluble in organic solvents and able to form robust and transparent film upon spin casting. Instrument characterization, such as FTIR, ¹H and ¹³C NMR, UV-vis and fluorescence spectroscopy, revealed the final structures as designed and novel photophysical properties in solution. Apparent spectral evidences strongly suggested the all trans conjugated DE-1 and -2 and the successful isomeirization process adopted. It was found that the aggregates were formed for both DE-1 and -2 at approximately 60% of methanol in methanol/dichloromethane (MeOH/DCM). Both DE-1 and -2 exhibited solution tailorable absorption and emission properties. Before aggregating point, the absorption profile experienced a blue shift with the increase of MeOH and a slight increase in quantum yields (QYs). At aggregating point, however, an apparent blue shift in emission profile was observed along with a remarkable decrease of QY due to aggregate quenching.     

Crystal structure of tris (phenylammonium) chloride pentachloroantimonate (III) monohydrate

The tris (phenylammonium) chloride pentachloroantimonate (III) monohydrate salt is triclinic with the following cell parameters: a = 9.4283(3), b = 11.4482(3), c = 13.1748(3)Å, = 113.493(2), = 90.381(2), = 97.331(1)°, V = 1290.86(6)ų, with Z = 2 formula units. The structure consists of [C₆H₅NH₃]⁺ cations, water molecules, Cl^– anions, and SbCl₅ square pyramids. Hydrogen bonds, established through water molecule, link the anions [SbCl₅]^2– and Cl^– and make an infinite chain in the [011] direction. Chains are linked together via another hydrogen bond network originating from the ammonium groups. A distortion of the SbCl₅ square pyramid can be attributed to the stereo activity of the Sb(III) lone electron pair.     

Crystal structure of a new double salt hydrate SrCd2Cl6⋅8H2O

SrCd₂Cl₆8H₂O crystallizes in the space group and has the unit cell dimensions a = 9.688(2) Å, b = 11.212(2) Å, c = 7.732(3) Å, = 99.85(21)°, = 89.95(22)°, = 75.81(13)°, and Z = 2. After refinement through full-matrix least-squares methods, the reliability factor R in the final cycle is 4.65%. A very persistent occurrence of twinning by pseudosymmetry was observed. The twin element is a twofold axis [001]. The title compound exhibits five endothermic peaks, which have been detected by differential scanning calorimetry and interpreted from thermogravimetry.     

Crystal structure of di(N-benzyl piperidinium) pentachloroantimonate(III) dihydrate

The salt di(N-benzyl piperidinium) pentachloroantimonate(III) dihydrate crystallizes in the orthorhombic system with space group Cmc2₁, the unit cell dimensions are: a = 29.383(1), b = 10.509(2), c = 9.941(1) Å, with Z = 8. The structure shows a layer arrangement perpendicular to the a axis: planes of SbCl₆ octahedra alternate with planes of [C₁₂H₁₇N]⁺ cations. The SbCl₆ octahedra are connected through a O(W)–HCl hydrogen bonds and a chlorine bridge, so that infinite unidimensional chains of composition [SbCl₅(H₂O)₂]^2n– _n are formed in the structure along the c direction. These chains are connected to [C₁₂H₁₇N]⁺ entities by N–HCl and N–HO(W) hydrogen bonds, forming a three-dimensional network. It was found that lengths of Sb–Cl bonds may differ from each other. The differences shown as a distortion of the SbCl₆ octahedra were attributed to the Sb(III) lone electron pair stereoactivity.