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The novel iron selenidostannates [Fe(bipy)3]Sn4Se9·2H2O (1) and [Fe(bipy)3]2[Sn3Se7]2·bipy·2H2O (2) (bipy = bipyridine) were prepared by the reactions of Sn, Se, FeCl2·4H2O, bipy, and dien with/without KSCN under hydrothermal conditions (dien = diethylenetriamine). In 1, four SnSe5 units condense via edge sharing to form the novel 3-D framework selenidostannate ∞³[Sn4Se92-] containing an interpenetrating channel system. The [Fe(bipy)3]2+ cations are accommodated in the different channels according to the conformation of the [Fe(bipy)3]2+ cation. In 2, three SnSe5 units share edges to form a 2-D ∞²[Sn3Se72-] layered anion, while two SnSe5 units and one SnSe4 unit are connected via edge sharing, forming a 1-D ∞¹[Sn3Se72-] chainlike anion. The ∞¹[Sn3Se72-], [Fe(bipy)3]2+, bipy, and H2O species are embedded between the ∞²[Sn3Se72-] layers. 2 is the first example of a selenidostannate constructed by both ∞²[Sn3Se72-]and ∞¹[Sn3Se72-] anions. The coexistence of 1-D ∞¹[Sn3Se72-] and 2-D ∞²[Sn3Se72-] anions in 2 might support the possible reaction mechanism that the ∞²[Sn3Se72-] anions are formed by condensation of the ∞¹[Sn3Se72-] chains. 1 and 2 exhibit band gaps at 1.43 and 2.01 eV, respectively [ABSTRACT FROM AUTHOR]

A sequential one-pot two-step tandem reaction for efficient synthesis of polysubstituted cyclopropanes has been developed. The three-component reaction of α-halogenated methylene compounds, aromatic aldehydes, and acetonitrile derivatives produced first the intermediates pyridinium salts and electron-deficient olefins, followed by cyclopropanation of pyridinium ylide with electron-deficient olefins in situ to afford polysubstituted cyclopropanes. Target compounds were obtained in high yields and were diastereomerically pure after recrystallization. [ABSTRACT FROM AUTHOR]

Micromixing is a crucial step for biochemical reactions in microfluidic networks. A critical challenge is that the system containing micromixers needs numerous pumps, chambers, and channels not only for the micromixing but also for the biochemical reactions and detections. Thus, a simple and compatible design of the micromixer element for the system is essential. Here, we propose a simple, yet effective, scheme that enables micromixing and a biochemical reaction in a single microfluidic chamber without using any pumps. We accomplish this process by using natural convection in conjunction with alternating heating of two heaters for efficient micromixing, and by regulating capillarity for sample transport. As a model application, we demonstrate micromixing and subsequent polymerase chain reaction (PCR) for an influenza viral DNA fragment. This process is achieved in a platform of a microfluidic cartridge and a microfabricated heating- instrument with a fast thermal response. Our results will significantly simplify micromixing and a subsequent bio- chemical reaction that involves reagent healing in microfluidic networks. [ABSTRACT FROM AUTHOR]

A new type of molecularly imprinted polymer (MIP)-based room-temperature phosphorescence (RTP) optosensor was developed by anchoring the MIP layer on the surface of Mn-doped ZnS quantum dots (QDs) via a surface molecular imprinting process. The synergetic combination of the RTP property of the Mn-doped ZnS QDs and the merits of the surface imprinting polymers not only improves the RTP selectivity of the Mn-doped ZnS QDs but also makes the MIP-based RTP optosensor also applicable to selective detecting of those nonphosphorescent analytes without the need for any inducers and derivatization. The new MIP-based RTP sensing protocol was applied to detect trace pentachlorophenol (PCP) in water samples without the interference of autofluorescence and scattering light of matrixes. The detection limit for PCP was 86 nM, and the precision for five replicate detections of 0.4 μM PCP was 2.8% (relative standard deviation). The recovery of spiked PCP in river water samples ranged from 93% to 106%. [ABSTRACT FROM AUTHOR]

Polysubstituted pyrido[1,2-α]benzimidazole derivatives are efficiently produced in moderate yields in a novel one-pot, four-component reaction from pyridine or 3-picoline, chloroacetonitrile, malononitrile, and aromatic aldehyde in refluxing acetonitrile. The mechanism of this novel reaction was believed involving the formation of polysubstituted benzenes with subsequent substitution and annulation reaction of pyridine. All pyrido[1,2-α]benzimidazoles, polysubstituted benzenes, polysubstituted indoles, and some key reaction intermediates are characterized by 1H and 13C NMR, MS, IR spectra, and elemental analysis as well as X-ray crystallography. [ABSTRACT FROM AUTHOR]

Ethanol oxidation on Pt is a typical multistep and multiselectivity heterogeneous catalytic process. A comprehensive understanding of this fundamental reaction would greatly benefit design of catalysts for use in direct ethanol fuel cells and the degradation of biomass-derived oxygenates. In this work, the reaction network of ethanol oxidation on different Pt surfaces, including close-packed Pt{111}, stepped Pt{211}, and open Pt{100}, is explored thoroughly with an efficient reaction path searching method, which integrates our new transition-state searching technique with periodic density functional theory calculations. Our new technique enables the location of the transition state and saddle points for most surface reactions simply and efficiently by optimization of local minima. We show that the selectivity of ethanol oxidation on Pt depends markedly on the surface structure, which can be attributed to the structure-sensitivity of two key reaction steps: (i) the initial dehydrogenation of ethanol and (ii) the oxidation of acetyl (CH3CO). On open surface sites, ethanol prefers C-C bond cleavage via strongly adsorbed intermediates (CH2CO or CHCO), which leads to complete oxidation to CO2. However, only partial oxidizations to CH3CHO and CH3COOH occur on Pt{111}. Our mechanism points out that the open surface Pt(100) is the best facet to fully oxidize ethanol at low coverages, which sheds light on the origin of the remarkable catalytic performance of Pt tetrahexahedra nanocrystals found recently. The physical origin of the structure-selectivity is rationalized in terms of both thermodynamics and kinetics. Two fundamental quantities that dictate the selectivity of ethanol oxidation are identified: (i) the ability of surface metal atoms to bond with unsaturated C-containing fragments and (ii) the relative stability of hydroxyl at surface atop sites with respect to other sites. [ABSTRACT FROM AUTHOR]