A Homotelechelic bis‐terpyridine macroligand: One‐step synthesis and its metallo‐supramolecular self‐assembly

A homotelechelic macroligand bearing two 2,2′:6′,2″‐terpyridin‐4′‐yl units, as chain ends, is used as building block for the preparation of a linear metallo‐supramolecular chain‐extended polymer. The macroligand has been prepared by nitroxide‐mediated polymerization (NMP) of styrene using a bis‐terpyridine‐functionalized NMP initiator. The controlled character of the NMP process has been confirmed by detailed characterization of the polymer by size‐exclusion chromatography, nuclear magnetic resonance spectroscopy as well as mass spectrometry. Subsequently, the self‐assembly with Fe^II ions into the chain‐extended metallopolymer and the disassembly thereof, in the presence of a strong competitive ligand, has been studied by UV–vis absorption spectroscopy and diffusion‐ordered NMR spectroscopy. The reversibility of the formation of the metallo‐supramolecular material, when addressed by external stimuli, could be proven. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Influence of Doping Different Rare Earth Ions on the Luminescence of CaTiO3‐based Phosphors

This paper reports the Gd³⁺, Dy³⁺, Tb³⁺ and Lu³⁺ doped CaTiO₃ based phosphors were synthesized by modified solid‐state reaction method and its crystal structure and luminescent properties were investigated. The X‐ray diffraction patterns (XRD) showed that the phosphors sintered at 1000 °C for 2 h were a pure CaTiO₃ phases. The optimization of reaction conditions were carried out by thermal gravimetry and differential thermal analysis methods (DTA/TG). Surface and elemental analyses were performed by using on SEM instrument. The excitation and emission spectras were recorded by photoluminescence spectrophotometer (PL).     

A multi-objective optimization approach for invasive species control

In this paper, we formulate and analyse a long-term multi-objective dynamic model for controlling invasive species. This optimization framework is then applied to the case of buffelgrass control in the Arizona desert. The proposed model simultaneously optimizes three objectives corresponding to three different valued and threatened resources including saguaros (a native cactus species), buildings and vegetation. The model is used to decide the optimal allocation of labour to these resources to control the population of the species in a multi-period planning horizon. The computational method to solve this problem is based on multi-objective integer programming.     

The synthesis of some new imidazole and triazole derivatives: crystal Structure and DFT-TDDFT investigation on electronic structure

A series of new N′-3-(1H-imidazol-1-yl)propylcarbamoyl-4-halogenebenzo hydrazonate (3a–b) were obtained by reaction Ethyl 2-((4-halogene phenyl) (ethoxy) methylene) hydrazinecarboxylate (1) and N-(3-aminopropyl)imidazole (2) at 120–140 °C. Compounds (4a–b) were obtained by the reaction compound 1 and N-(3-aminopropyl)imidazole (2) at 160–180 °C. The structures of compounds 3,4 have been inferred through UV–Vis, IR, ¹H/¹³C NMR, mass spectrometry, elemental analyses, and X-ray crystallography. DFT level 6-31G (d) calculations provided structural information. The electronic structure of compound 3a has been studied by DFT level 6-31G (d) calculations using the X-ray data. The results are accordance with X-ray data.     

Stereo-selectivity in a cyclotriphosphazene derivative bearing an exocyclic P-O moiety

Nucleophilic substitution reactions of N(3)P(3)Cl(4)[O(CH(2))(2)NCH(3)], (1) with the sodium salts of mono- and di-functional alcohols [methanol (2), phenol (3), tetraethyleneglycol (4) and 1,3-propanediol (5)] were carried out in order to investigate a possible directing effect of the spiro O-moiety on the formation of mono-substituted (2a, 3a), non-geminal di-substituted (2c, 3c) and ansa (4a, 5a) derivatives. Compounds isolated from the reactions were characterized by elemental analysis, mass spectrometry, (1)H and (31)P NMR spectroscopy and X-ray crystallographic analysis showed that the substituent OR in compounds (2a, 3a and 2c, 3c) and the ansa-ring in compounds (4a, 5a) formed cis to the P-O moiety of the exocyclic [O(CH(2))(2)NCH(3)] spiro ring. The formation of products (2a-d, 3a-d, 4a, 5a and 5b) was quantified from the (31)P NMR spectra of the reaction mixtures, which showed an overwhelming preference for derivatives (2a, 3a, 2c, 3c, 4a, 5a) with the substituent cis to the P-O moiety of the exocyclic spiro ring (2a, 3a, 2c, 3c, 4a, 5a), except for reaction with 1,3-propanediol where the six-membered ring spiro derivative (5b) was about three times more abundant than the eight-membered ring ansa-derivative (5a). Overwhelming formation of products with the substituent cis to the exocyclic P-O moiety is proof that the cation-assisted mechanism is responsible for the stereo-selectivity in the reactions with alkoxides.     

Determination of the relative ligand‐binding strengths in heteroleptic IrIII complexes by ESI‐Q‐TOF tandem mass spectrometry

An electrospray ionization quadrupole time‐of‐flight mass spectrometer has been utilized to investigate the relative ligand‐binding strengths in a series of heteroleptic‐charged iridium(III) complexes of the general formula [(C^N)₂Ir^III(S‐tpy)](PF₆) by using variable collision energies. Collision‐induced dissociation experiments were performed in order to study the stability of the Ir^III complexes that are, for instance, suitable phosphors in light‐emitting electrochemical cells. The ratio of signal intensities belonging to the fragment and the undissociated complex depends on the collision energy applied for the tandem mass spectra (MS/MS) analysis. By defining the threshold collision energy and the point of complete complex dissociation, it is possible to estimate the relative complex stabilities depending on the nature of the coordinated ligands [i.e. type of cyclometalating ligand (C^N), substituents on the S‐shaped terpyridine (S‐tpy)]. The collision energy values differed as a function of the coordination sphere of the Ir^III centers. Copyright © 2011 John Wiley & Sons, Ltd.     

Synthesis and phosphorescence properties of Dy3+ and (Pr3+–Dy3+) in MgTiO3

Using tetra-n-butyl titanate and magnesium nitrate as raw materials, Dy³⁺ and Pr³⁺ ions in the matrix of magnesium titanate (MgTiO₃) was successfully synthesized by a modified solid-state reaction. The mixtures to achieve a solid-state reaction were heated in porcelain crucibles at 600?°C for 2?h, 900?°C for 6?h, and 1000.0?°C for 2?h. The reaction products obtained in an air atmosphere were characterized by X-ray powder diffractions. The optimization of reaction conditions were carried out by thermal gravimetry and differential thermal analysis methods. Surface and elemental analyses were performed by using on SEM instrument. The excitation and emission spectra were recorded by photoluminescence spectrophotometer.     

On-line speciation and determination of Cr(III) and Cr(VI) in drinking and waste water samples by reversed-phase high performance liquid chromatography coupled with atomic absorption spectrometry

A simple, rapid, and selective on-line method for the speciation and determination of Cr(III) and Cr(VI) in aqueous solutions by ion-pairing HPLC coupled with flame atomic absorption spectrometry (FAAS) is described. The composition of the mobile phase has been optimized for better separation. The effects of column temperature, volume of injection loop, fuel flow rate of FAAS, and nebulizer suction rate of FAAS have also been investigated. Separation is accomplished in almost 2.5 min on a 25 cm length C18 column at 40 degrees C. The selectivity of the method has been established by investigating the effect of interfering elements on chromium determination. The detection limit (3sigma) achieved by the method was calculated as 3.7 ng/mL for Cr(III) and 2.0 ng/mL for Cr(VI). The proposed method has been validated by analyzing certified reference material (BCR 544) and successfully applied to the analysis of drinking water and wastewater samples with a relative error below 6%.     

Fabrication of ultrahydrophobic poly(lauryl acrylate) brushes on silicon wafer via surface-initiated atom transfer radical polymerization

In this report, ultrahydrophobic poly(lauryl acrylate) [poly(LA)] brushes were synthesized by surface-initiated atom transfer radical polymerization (SI-ATRP) of lauryl acrylate (LA) in N,N-dimethylformamide (DMF) at 90 °C. The formation of ultrahydrophobic poly(LA) films, whose thickness can be turned by changing polymerization time, is evidenced by using the combination of ellipsometry, X-ray photoelectron spectroscopy (XPS), grazing angle attenuated total reflectance-Fourier transform infrared spectroscopy (GATR-FTIR), atomic force microscopy (AFM), gel permeation chromatography (GPC), and water contact angle measurements. The SI-ATRP can be conducted in a well-controlled manner, as revealed by the linear kinetic plot, linear evolution of number-average molecular weights () versus monomer conversions, and the relatively narrow PDI (<1.28) of the grafted poly(LA) chains. The calculation of grafting parameters from experimental measurements indicated the synthesis of densely grafted poly(LA) films and allowed us to predict a “brushlike” conformation for the chains in good solvent. The poly(LA) brushes exhibited high water contact angle of 163.3 ± 2.8°.     

Near‐IR‐Triggered,Remote‐Controlled Release of Metal Ions: A Novel Strategy for Caged Ions

A ligand incorporating a dithioethenyl moiety is cleaved into fragments which have a lower metal‐ion affinity upon irradiation with low‐energy red/near‐IR light. The cleavage is a result of singlet oxygen generation which occurs on excitation of the photosensitizer modules. The method has many tunable factors that could make it a satisfactory caging strategy for metal ions.