Molecular Iodine in Ionic Liquid: A Green Catalytic System for Esterification and Transesterification

Esterification of carboxylic acids and transesterification of β-ketoesters with alcohols have been developed using a catalytic amount of iodine in polyethylene glycol (PEG) ionic liquid (IL 1000) to afford the corresponding esters in good yields. By simple separation of the ionic-liquid phase containing the iodine, the system of I₂/IL 1000 can be reused several times.     

Novel bimetallic Cr<Subscript>3</Subscript>Yb<Subscript>3</Subscript> mixed salt containing a 3<Emphasis Type="Italic">d</Emphasis>-4<Emphasis Type="Italic">f</Emphasis> heterometallic Cr<Subscript>2</Subscript>Yb<Subscript>3</Subscript> cluster

A novel bimetallic Cr₃Yb₃ coordination compound containing a 3d-4f heterometallic Cr₂Yb₃ cationic cluster has been synthesized and structurally characterized. The crystal structure was determined by X-ray analysis. Results denote that the complex consists of an original [Cr ₂ ^III Yb ₃ ^III ]³⁺ moiety with a trigonal-bipyramidal topology of the [Cr₂Yb₃(μ-OOCCH₃)₆(μ-OH)₆(H₂O)₆]³⁺ core, an isolated [Cr^III(CN)₆]^3? anion, and four molecular neutral 4,4′-bipyridene (Bipy) ligands, namely, [Cr₂Yb₃(μ-OOCCH₃)₆(μ-OH)₆(H₂O)₆][Cr(CN)₆] · 4Bipy · 13H₂O.     

Photocontrolled Multidirectional Differentiation of Mesenchymal Stem Cells on an Upconversion Substrate

The effective guidance of mesenchymal stem cell (MSC) differentiation on a substrate by near‐infrared (NIR) light is particularly attractive for tissue engineering and regenerative medicine. However, most of current substrates cannot control multidirectional differentiation of MSCs like natural tissues. Herein, a photocontrolled upconversion‐based substrate was designed and constructed for guiding multidirectional differentiation of MSCs. The substrate enables MSCs to maintain their stem‐cell characteristics due to the anti‐adhesive effect of 4‐(hydroxymethyl)‐3‐nitrobenzoic acid modified poly(ethylene glycol) (P1) attached on the upconversion substrate. Upon NIR irradiation, the P1 is released from the substrate by photocleavage. The detachment of P1 can change cell–matrix interactions dynamically. Moreover, MSCs cultured on the upconversion substrate can be specifically induced to differentiate to adipocytes or osteoblasts by adjusting the NIR laser. Our work provides a new way of using NIR‐based upconversion substrate to modulate the multidirectional differentiation of MSCs.     

Experimental Evidence for a Triboluminescent Antiperovskite Ferroelectric: Tris(trimethylammonium) catena‐Tri‐μ‐chloro‐manganate(II) Tetrachloromanganate(II)

The perovskite structure is rich in ferroelectricity. In contrast, ferroelectric antiperovskites have been scarcely confirmed experimentally since the discovery of M₃AB‐type antiperovskites in the 1930s. Ferroelectricity is now revealed in an organic–inorganic hybrid X₃AB antiperovskite structure, which exhibits a clear ferroelectric phase transition 6/mmmF6mm with a high Curie point of 480 K. The physical properties across the phase transition are obviously changed along with the symmetry requirements, providing solid experimental evidence for the ferroelectric phase transition. More interestingly, the discovered antiperovskite shows intense photoluminescence and triboluminescence properties. The confirmation of the triboluminescent ferroelectric antiperovskite will open new avenues to explore excellent optoelectronic properties in the antiperovskite family.     

Physicochemical properties of sodium succinate sulfate and effects on BaSO4 suspension

Sodium succinate sulfate (MAPEG1500-OSO₃Na) was prepared using maleic anhydride (MA) and polyethylene glycols (PEG1500) as raw materials. The structure was characterized by Fourier transform infrared spectrometry (FTIR) and ¹H-nuclear magnetic resonance (¹H NMR). Its physicochemical properties, such as surface activity, adsorption behavior, spreading performance, and rheological property, were investigated by static/dynamic surface tension (DST) measurements, contact angle techniques, and rheological techniques at 25°C. Surface tension measurement for this surfactant is about 17?mN/m. The DST results indicated that the adsorption process is mixed diffusion-kinetic adsorption mechanism. The spreading measurement demonstrated that MAPEG1500-OSO₃Na possessed an excellent spreading ability. Besides, the dispersion performances of MAPEG1500-OSO₃Na on barium sulfate (BaSO₄) particles under different conditions have been studied by the weighing method and transmission electron microscope (TEM). These results showed that there exist optimum pH value and added amount of MAPEG1500-OSO₃Na corresponding to the highest dispersion rate.     

Suzuki-Miyaura cross-coupling reaction of aryl chlorides with aryl boronic acids catalyzed by a palladium dichloride adduct of N-diphenylphosphanyl-2-aminopyridine

One palladium dichloride adduct of a phosphine-pyridine ligand N-diphenylphosphanyl-2-aminopyridine (L₁) [(L₁)PdCl₂] (1) has been prepared and structurally characterized. Compound 1 can be used as an effective catalyst for the Suzuki-Miyaura cross-coupling reactions of unreactive aryl chlorides with aryl boronic acids, and worked much better than its mono- or bidentate phosphine ligands. The reactions with a wide scope of substrates proceeded to give desired products in good to excellent yields.     

Synthesis of a sialic acid dimer derivative, 2'alpha-O-benzyl Neu5Ac-alph-(2-->5)Neu5Gc

The preparation of a disaccharide 2, Neu5Ac-alpha-(2-->5)Neu5Gc having a alpha-benzyl protecting group at the reducing end, by the coupling of the easily accessible building units 4 and 5 is described. Subsequent deprotection of the coupling adduct led to the isolation of the target compound 2 in high yield.     

Shear‐induced structuring kinetics in thermoplastic segmented polyurethanes monitored by rheological tools

Thermoplastic segmented polyurethanes (TPUs) are an important class of thermoplastic elastomers with a two‐phase microstructure arising from the thermodynamic incompatibility between hard (HSs) and soft segments. This microphase separation observed on cooling from a homogeneous state is often combined with the solidification of either or both types of segments. In this study, the structuring mechanism of two TPUs with HSs based on 4,4′‐diphenylmethane diisocyanate and 1,4‐butanediol was investigated from rheological measurements. Hence, in addition to the structuring temperature influence, the effect of an applied preshear flow in the melt polymer was analyzed, in particular. The results clearly show an enhancement of the solidification kinetics by the preshear. Indeed, the measured structuring time can be reduced by more than 1 decade. Rheo‐optical microscopy observations coupled with a shearing hot stage corroborated these results and showed the modification of the microstructure by the shear. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 190–201, 2010