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Two new cyano-bridged one-dimensional heterobimetallic coordination polymers and a trinuclear complex are synthesized using tailored tricyanometalate precursor. Complex [(bpca)2Fe(super III)2(CN)6Mn(CH3OH)2(H2O)2] displays metamagnetic behavior with a Neel temperature of T(sub N) = 2.2 K and a weak critical field of 250 Oe at 1.8 K.

One-dimensional chiral copper(II) and manganese(II) coordination polymers with single asymmetric end-to-end azide bridges are synthesized, using azide ions as bridging groups and chiral Schiff bases as auxiliary ligands. The findings reveal that they all crystallize in the chiral space group P2I.

Two homochiral trinuclear heterobimetallic clusters are prepared and structurally characterized. Ferroelectric and magnetic measurements have shown that these clusters are rare examples of metal-organic compounds bearing ferroelectricity and intramolecular ferromagnetic interactions.

The tricyano precursor ([Bu.sub.4]N)[[(Tp)Fe(CN).sub.3]] (Tp = tris(pyrazolyl) hydroborate) was utilized to synthesize four new tetranuclear clusters and study their magnetic properties and the factors that might affect single-molecule magnet (SMM) properties. Different magnetic properties from ferromagnetism to SMM-like and spin-glass-like behaviors are observed in these clusters with nearly the same geometry and topology which is determined by the single ion anisotropy and the distortion of the molecular structure.

The syntheses, crystal structures, and magnetic properties of four one-dimensional cyanobridged heterobimetallic chain complexes are presented. Complexes [(TP)2[Fe.sub.2.sup.III](CN)6Cu(CH3OH).2CH3OH]n and [(TP)2[Fe.sub.2.sup.III](CN)6Cu(DMF).DMF]n ( Tp=tris(pyrazolyl)hydroborate ) show single chain magnets behavior.

The synthesis and characterization of two enantiopure one-dimensional complexes with helical structures, [[M[n.sub.3][((R,R).Salcy).sub.3][([H.sub.2]O].sub.2]Fe[(CN).sub.6].2[H.sub.2]O].sub.n] and [[M[n.sub.3][((S,S).Salcy).sub.3][([H.sub.2]O].sub.2]Fe[(CN).sub.6].2[H.sub.2]O].sub.n] is reported. Magnetic studies reveal both complexes to be ferrimagnets with their magnetic transition temperature at 3 K.

A tridentate blocking ligand on the Cu(super II) centers is used to generate a trigonal bipyramidal cluster, [Tp(sub 2)(Me(sub 3)tacn)(sub 3)Cu(sub 3)Fe(sub 2)(CN)(sub 6)](super 4+), in which the reduced symmetry affords a significantly increased anisotropy barrier. The results have shown the enormous impact that cluster symmetry can have on magnetic anisotropy, with a ligand-induced switch from a cubic to a linear arrangement of Fe(super III) centers leading to the enhancement of the anisotropy barrier.

Voacafricines A and B, two unique monoterpenoid indole alkaloids each bearing five fused heterocycles, were obtained from the fruits of Voacanga africana. Their structures were elucidated by extensive spectroscopic methods and computational studies. A plausible biogenetic pathway was proposed from a common precursor, 19-epi-voacristine. Both compounds exhibited potent activity against Staphylococcus aureus and Salmonella typhi, and their activities were superior to those of the well-known antibacterial drugs berberine and fibrauretine. [ABSTRACT FROM AUTHOR]

Herein, we report a new facile and safe pathway for the scaled-up production of mechanically strong and multiresponsive interpenetrating polymer network (IPN) hydrogels via multichannel frontal polymerization (multichannel FP). We designed a two-part system, of which part-1 contained high reactive monomer and could polymerize spontaneously. The polymerization of part-1 released tremendous amount of heat, subsequently initiating FP of part-2 to convert monomers to polymers without any external energy, which is flexible, cost-effective, and environmental. Multichannel FP not only allowed realization of parallel polymerization to obtain a number of hydrogels but also solved center overheating and explosion problem stemmed from a large reaction vessel. Compared with the sample prepared in bigger tubular reactor, product synthesized via multichannel FP showed more excellent thermal stability, morphology and mechanical properties. Moreover, the as-prepared IPN hydrogels exhibited chemical-, pH-, and thermal-sensitivity toward various external changes, which might broaden the applications of hydrogels in sensors. [ABSTRACT FROM AUTHOR]

With rapid progress in the use of colloidal quantum dots (QDs) as light emitters, the next challenge for this field is to achieve high brightness. Unfortunately, Auger recombination militates against high emission efficiency at multiexciton excitation levels. Here, we suppress the Auger-recombination-induced photoluminescence (PL) quantum yield (QY) loss in CdSe/CdS core-shell QDs by reducing the absorption cross section at excitation wavelengths via a thin-shell design. Studies of PL vs shell thickness reveal that thin-shell QDs better retain their QY at high excitation intensities, in stark contrast to thicker-shell QDs. Ultrafast transient absorption spectroscopy confirms increased Auger recombination in thicker-shell QDs under equivalent external excitation intensities. We then further grow a thin ZnS layer on thin-shell QDs to serve as a higher conduction band barrier; this allows for better passivation and exciton confinement, while providing transparency at the excitation wavelength. Finally, we develop an isolating silica matrix that acts as a spacer between dots, greatly reducing interdot energy transfer that is otherwise responsible for PL reduction in QD films. This results in the increase of film PL QY from 20% to 65% at low excitation intensity. The combination of Auger reduction and elimination of energy transfer leads to QD film PL QY in excess of 50% and absolute power conversion efficiency of 28% at excitation powers of 1 kW/cm2, the highest ever reported for QDs under intense illumination. [ABSTRACT FROM AUTHOR]

Wereport the synthesis of a new type of triple stimuli-responsive,i.e., thermo-, pH-, and metal ion-responsive copolymers based on poly(N-vinylimidazole-co-methacrylic acid) (poly(VI-co-MAA)) and their application as metal ion sensors. Thecopolymers exhibit reversible sol–gel phase transition behaviorin aqueous media. The sol-to-gel transition temperature (Tsol–gel) can be shifted in the range of 20–80°C, by varying monomer ratio and feeding glycerol content, byadjusting the copolymer concentration in aqueous solution, by tuningthe pH of the solution, or by adding various divalent metal ions.Metal ion sensors were designed upon an inverse opal photonic filmloaded with aqueous solution of poly(VI-co-MAA),which allows the easy reorganization of various divalent metal ionsby combining the diversity of Tsol–gelof the copolymers on different metal ions and flexible reflectionspectra of the film. In addition, a fluorescent reversible sol–geltransition system was established by in situgenerationof nanocrystals in the copolymer matrix. These extensions may providethe multiresponsive copolymers great flexibility for applicationsin biomedical, optical, and sensory fields. [ABSTRACT FROM AUTHOR]

Allene-containingphosphines have recently been shown to serveas effective ligands in transition metal-catalyzed enantioselectivereactions. Surprisingly, (2-allenylphenyl)diphenyl phosphines rapidlyoxidize when exposed to air, whereas many other triaryl phosphinesare stable under ambient conditions. Here we describe experimentsdesigned to understand the origin of this behavior. Stereochemicalprobes and an isolated phosphonium complex support the hypothesisthat phosphines can cyclize onto pendant allenes and that the resultantzwitterion undergoes rapid oxidation with molecular oxygen. [ABSTRACT FROM AUTHOR]

Assembly of inorganic semiconductor nanocrystals into polymer host is of great scientific and technological interest for bottom-up fabrication of functional devices. Herein, an interface-directed synthetic pathway to polymer-encapsulated CdTe quantum dots (QDs) has been developed. The resulting nanohybrids have a highly uniform fibrous architecture with tunable diameters (ranging from several tens of nanometers to microscale) and enhanced optical performance. This interfacial assembly strategy offers a versatile route to incorporate QDs into a polymer host, forming uniform one-dimensional nanomaterials potentially useful in optoelectronic applications. [ABSTRACT FROM AUTHOR]