Synthesis and characterization of thiochromone S,S-dioxides as new photolabile protecting groups

3-Arylthiochromone derivatives were synthesized as new photolabile protecting groups, in which the photoreactivity was switchable based on oxidation of the sulfur atom (sulfide and sulfone); the protected substrates , released the corresponding alcohols, amines or carbonxylic acids almost quantitatively under UV-light in neutral condition and the photoproduct showed high fluorescence intensity.     

A series of luminescent Cu(I) mixed-ligand complexes containing 2,9-dimethyl-1,10-phenanthroline and simple diphosphine ligands

A series of Cu(I) mixed-ligand complexes containing dmp (2,9-dimethyl-1,10-phenanthroline) and one of simple diphosphine ligands (Ph2P(CH2)nPPh2) were prepared. Among the complexes, [Cu(dppp)(dmp)]PF6 (n=3) and [Cu2(dppb)2(dmp)2](PF6)2 (n=4) were characterized by X-ray structure analyses. The dppp complex has been characterized as a mononuclear complex, while [Cu2(dppb)2(dmp)2]2+ exists as a dinuclear complex in which two dppb ligands bridge between the two Cu(I) atoms. Although the distorted tetrahedral structures around the central metals of the two complexes are similar, the P-Cu-P angles are different between the two complexes. All of the series of complexes show photoluminescence in solution, and the intensity of the luminescence increases with n (n=2-4). The non-radiative rate constants of the complexes decrease markedly with n although radiative rate constants of the complexes are similar.     

Fully automated liquid chromatography-mass spectrometry determination of 17beta-estradiol in river water

Surface modified molecularly imprinted polymers (SM-MIPs) for 17beta-estradiol (E2), utilizing 6-ketoecradiol as a pseudo template were prepared. MIPs for E2 were synthesized using 4-vinyl pyridine and ethylene dimethacrylate as a functional monomer and cross-linking agent, respectively. MIPs selectively retained E2 and provided excellent chromatographic resolution from interfering compounds inherent in river water sample matrices. Therefore, freshly prepared MIPs were applied to quantitative mass spectrometric (negative electrospray ionization mode) detection of low levels of E2 in river water sample. In order to pre-concentrate the target compound for HPLC analysis, column switching was coupled with a pretreatment column packed with the MIPs. The repeatability of actual determinations of river water sample, in which background E2 was not detected, spiked with 50 ng/L of E2 was 2.2% RSD with a detection limit and qualification limit of 1.8 and 5.4 ng/L, respectively. Surface modification of MIP particlefs packed in the pretreatment column provided selective affinity and on-line concentration of low levels of E2 while simultaneously eliminating sample matrix interference, resulting in a significant increase in sensitivity and reproducibility for liquid chromatography-mass spectrometry analysis of E2 in river water sample.     

Enantioselective Synthesis of Tetra-ortho-Substituted Axially Chiral Biaryls through Rhodium-Catalyzed Double [2 + 2 + 2] Cycloaddition

[reaction: see text] We have established an enantioselective synthesis of both C2 symmetric and unsymmetric tetra-ortho-substituted axially chiral biaryls through rhodium-catalyzed double [2 + 2 + 2] cycloaddition (up to >99% ee). This method serves as an attractive new route to enantioenriched tetra-ortho-substituted axially chiral biaryls in view of the one-step access to substrate diynes and tetraynes starting from readily available alkynes.     

MOF‐on‐MOF: Oriented Growth of Multiple Layered Thin Films of Metal–Organic Frameworks

The precise alignment of multiple layers of metal–organic framework (MOF) thin films, or MOF‐on‐MOF films, over macroscopic length scales is presented. The MOF‐on‐MOF films are fabricated by epitaxially matching the interface. The first MOF layer (Cu₂(BPDC)₂, BPDC=biphenyl‐4,4′‐dicarboxylate) is grown on an oriented Cu(OH)₂ film by a “one‐pot” approach. Aligned second (Cu₂(BDC)₂, BDC=benzene 1,4‐dicarboxylate, or Cu₂(BPYDC)₂, BPYDC=2,2′‐bipyridine‐5,5′‐dicarboxylate) MOF layers can be deposited using liquid‐phase epitaxy. The co‐orientation of the MOF films is confirmed by X‐ray diffraction. Importantly, our strategy allows for the synthesis of aligned MOF films, for example, Cu₂(BPYDC)₂, that cannot be grown on a Cu(OH)₂ surface. We show that aligned MOF films furnished with Ag nanoparticles show a unique anisotropic plasmon resonance. Our MOF‐on‐MOF approach expands the chemistry of heteroepitaxially oriented MOF films and provides a new toolbox for multifunctional porous coatings.     

Determination of Monomer Unit Sequence Distribution and Linkage Configuration of Copolymers of Styrene and Citraconic Anhydride,and Possibility of a Participation of Electron Donor-Acceptor Complex in the Copolymerization

Abstract

The copolymerization system of styrene (ST) and citraconic (α-methymaleic) anhydride (CA) was found to form semi-alternating copolymers when polymerized with a total monomer concentration of 4 mol/L in CCl₄ at 50°C, with alternating copolymers being formed only when the CA mole fraction in feed was greater than 0.9. More than 50% of the linkage configurations at the cyclic CA units in the copolymers were found to be in cis configuration. This, together with the following observations, is consistent with a participation of the electron donor-acceptor (EDA) complex formed between ST and CA: (a) the complex participation model fits best, although only marginally, to the experimental triad mole fraction of alternating sequences; (b) the alternating monomer unit sequences and the cis linkage configuration at the cyclic CA units are more efficiently formed in non polar CCl₄ solutions than in polar methy ethyl ketone. The equilibrium constant for the EDA complexation of ST and CA in CCl₄ at 23°C is determined to be 0.142 ± 0.015 L/mol.     

Flame Retardancy and Kinetic Behavior of Ammonium Polyphosphate–Treated Unsaturated Polyester/Phenolic Interpenetrating Polymer Network

In this study, the flammability and kinetic behavior of flame retardant unsaturated polyester (UP)/phenolic resin were investigated. The flame retardant ammonium polyphosphate (APP) was used in this research to improve the flame resistance of a UP/phenolic resin interpenetrating polymer network (IPN). The flame resistance of UP improved from none to V-0 classification by adding phenolic resin and APP. Kinetic behavior study of UP, UP/phenolic, and APP-filled UP/phenolic IPN was carried out by the Borchardt and Daniels method. The results indicated that modification of flammable UP resin markedly improved the total heat release volume of UP and the flame retardancy of the IPN network structure was also enhanced.     

Intramolecular Benzyne–Phenolate [4+2] Cycloadditions

An intramolecular benzyne–phenolate [4+2] cycloaddition is reported. Benzyne precursors, having vicinal halogen‐sulfonate functionalities, linked with a phenol(ate) by various tether groups undergo efficient intramolecular [4+2] cycloaddition by treatment with either Ph₃MgLi or nBuLi for halogen–metal exchange to form various benzobarrelenes.     

Voltammetric Determination of Boric Acid Using the Ternary Complexation System with Salicylaldehyde and H‐Acid

A square‐wave voltammetric method for the determination of boric acid in water has been described based on the new understanding of the electrochemical behavior of boric acid‐Azomethine H complexation. Salicylaldehyde and H‐acid were used as the starting materials of boric acid‐Azomethine H complex and their concentrations were optimized for boric acid determination in water. A glassy carbon electrode, instead of a conventional mercury electrode, was used in the measurement. The detection limit of the proposed method was 0.10 mg B dm^?3. The proposed method was successfully used for boric acid determination in the water from a seawater desalination RO plant.     

Dynamics of ice nucleation on water repellent surfaces

Prevention of ice accretion and adhesion on surfaces is relevant to many applications, leading to improved operation safety, increased energy efficiency, and cost reduction. Development of passive nonicing coatings is highly desirable, since current antiicing strategies are energy and cost intensive. Superhydrophobicity has been proposed as a lead passive nonicing strategy, yet the exact mechanism of delayed icing on these surfaces is not clearly understood. In this work, we present an in-depth analysis of ice formation dynamics upon water droplet impact on surfaces with different wettabilities. We experimentally demonstrate that ice nucleation under low-humidity conditions can be delayed through control of surface chemistry and texture. Combining infrared (IR) thermometry and high-speed photography, we observe that the reduction of water-surface contact area on superhydrophobic surfaces plays a dual role in delaying nucleation: first by reducing heat transfer and second by reducing the probability of heterogeneous nucleation at the water-substrate interface. This work also includes an analysis (based on classical nucleation theory) to estimate various homogeneous and heterogeneous nucleation rates in icing situations. The key finding is that ice nucleation delay on superhydrophobic surfaces is more prominent at moderate degrees of supercooling, while closer to the homogeneous nucleation temperature, bulk and air-water interface nucleation effects become equally important. The study presented here offers a comprehensive perspective on the efficacy of textured surfaces for nonicing applications.