Structurally diverse coordination compounds of zinc as effective precursors of zinc oxide nanoparticles with various morphologies

The structurally diverse coordination compounds of zinc were designed and synthesized using two types of building blocks: short‐chain carboxylate ions and hexamethylenetetraamine. They were characterized by X‐ray crystallography, infrared spectroscopy and thermal analysis. The studied compounds were used as precursors for production (via controlled thermal conversion) of zinc oxide nanoparticles. The conversion process was optimized in terms of two parameters (heating rate and maximum temperature). Such an approach, combined with proper design of the precursor structure, allows fabrication of various zinc oxide micro‐ and nanoparticles. The influence of a precursor structure and modifications of conversion parameters on size and morphology of ZnO particles were studied and discussed.     

New Anthraquinone Derivatives as Electrochemical Redox Indicators for the Visualization of the DNA Hybridization Process

Interactions of dsDNA and ssDNA, at the surface of gold and silver electrodes, with three novel anthraquinone derivatives: 3‐(9′,10′‐dioxo‐9′,10′‐dihydro‐anthracen‐1‐yl)‐7,11‐di(carboxymethyl)‐3,7,11‐triazatridecanedioic acid, (AQ‐1); 1‐(9′,10′‐dioxo‐9′,10′‐dihydro‐anthracen‐1yl)‐9‐carboxymethyl‐5‐methyl‐1,5,9‐triazaundecanoicacid, (AQ‐2); and N‐(2‐(9,10‐dioxo‐9,10‐dihydro‐anthracen‐1‐ylamino)ethyl)‐2‐(1,4,10,13‐tetraoxa‐7,16‐diazacyclooctadecan‐7‐yl)acetamide, (AQ‐3) are studied. These derivatives are well soluble in water and phosphate buffer solutions. The square wave voltammetric behavior of these redox indicators is described and the parameters of interactions with DNA are reported. It is also pointed out that these compounds can be employed as the hybridization indicators. The difference in the binding ability of the particular redox indicator to single and double stranded DNA can be used for the detection of the complementary nucleic acids.     

Photophysical properties of a new DyLight 594 dye

We describe spectral properties of novel fluorescence probe DyLight? 594. Absorption and fluorescence spectra of this dye are in the region of Alexa 594 fluor spectra. The quantum yield of DyLight 594 in conjugated form to IgG is higher than corresponding quantum yield of Alexa 594 by about 50%. The new DyLight dye also shows slightly longer lifetime and photostability. These favorable properties and high anisotropy value, as well as a high cross-section for two-photon excitation, make this fluorophore attractive as a fluorescence probe in biochemical/biological studies involving fluorescence methods.     

Size Selection During Crystallization of Oppositely Charged Nanoparticles

Opposites attract (selectively) : Oppositely charged nanoparticles characterized by different size distributions form 3D supracrystals (see figure) only if the distributions overlap. Crystal quality decreases rapidly with decreasing degree of overlap, and, irrespective of the ratio of particle diameters/charges, no crystals are observed for non‐overlapping distributions.

     

Elucidating the Structural Chemistry of a Hysteretic Iron(II) Spin-Crossover Compound From its Copper(II) and Zinc(II) Congeners

Annealing [FeL₂][BF₄]₂ ⋅ 2 H₂O (L=2,6-bis-[5-methyl-1H-pyrazol-3-yl]pyridine) affords an anhydrous material, which undergoes a spin transition at T_1/2=205 K with a 65 K thermal hysteresis loop. This occurs through a sequence of phase changes, which were monitored by powder diffraction in an earlier study. [CuL₂][BF₄]₂ ⋅ 2 H₂O and [ZnL₂][BF₄]₂ ⋅ 2 H₂O are not perfectly isostructural but, unlike the iron compound, they undergo single-crystal-to-single-crystal dehydration upon annealing. All the annealed compounds initially adopt the same tetragonal phase but undergo a phase change near room temperature upon re-cooling. The low-temperature phase of [CuL₂][BF₄]₂ involves ordering of its Jahn–Teller distortion, to a monoclinic lattice with three unique cation sites. The zinc compound adopts a different, triclinic low-temperature phase with significant twisting of its coordination sphere, which unexpectedly becomes more pronounced as the crystal is cooled. Synchrotron powder diffraction data confirm that the structural changes in the anhydrous zinc complex are reproduced in the high-spin iron compound, before the onset of spin-crossover. This will contribute to the wide hysteresis in the spin transition of the iron complex. EPR spectra of copper-doped [Fe_0.97Cu_0.03L₂][BF₄]₂ imply its low-spin phase contains two distinct cation environments in a 2:1 ratio.     

Random Sequences Interpolating with Probability One

Let {_n} be a sequence of independent random variables uniformlydistributed on [0, 2], and let {r_n} be a sequence of (deterministic)radii in [0, 1). Form points of the unit disc putting z_n = r_ne_n.We characterize those sequences {r_n} for which {z_n} is an interpolatingsequence with probability one.     

Condensation Reaction of Dimethyltin(IV) Oxide with 2‐(2,3‐Dichloroanilino)benzoic Acid Synthesis and Study of a Novel Dimeric Tetraorganodistannoxane

The novel symmetric dimeric tetraorganodistannoxane [(Me₂Sn)₄(DCPA)₂)O₂(OH)₂] ( 2 ) and [(Me₂Sn)₄(DCPA)₂)O₂(OC₂H₅)₂] ( 3 ) where HDCPA is 2‐(2,3‐dichloroanilino)benzoic acid ( 1 ) have been prepared. The crystal structure of 3 has been determined by X‐ray crystallography. Three distannoxane rings are present to the centrosymmetric dimeric tetraorganodistannoxane by virtue of μ₃‐oxo form the central R₄Sn₂O₂ core with a planar Sn₂O₂ ring, resulting in a ladder type structural motif. Five‐coordinated tin atoms are present in the distannoxane dimer. The ligands act as monodentate agents, thus rendering the tin atom five‐coordinated. Significant π → π stacking interactions and intramolecular hydrogen bonds stabilize the structure 3 . The polar imino hydrogen atom participates in intramolecular hydrogen bonds. The formation of the dimeric distannoxanes 2 and 3 represent a ladder‐type carboxylates in which the insertion of a μ₂‐OH or a μ₂‐OC₂H₅ group occurs. This unusual result can be interpreted in terms of a competition between the strength different donors, in which the –OH or the –OC₂H₅ groups show higher donor capacity than the carboxylato group of DCPA.     

Biodegradable ionic liquids in service of biomass upgrade

This work presents an up-to-date overview of the use of biodegradable ionic liquids in the conversion of biomass in the context of biorefineries. Special attention is given to works in which biodegradability potentiates advanced application of ionic liquids in terms of process intensification for deployment of technologies towards bioenergy carriers or bioderived value-added products.     

Kinetic study of the reaction of OH with CH3I revisited

A flash photolysis resonance fluorescence technique has been employed to investigate the kinetics and mechanism of the reaction of OH(X²Π) radicals with CH₃I over the temperature and pressure ranges 295–390 K and 82–303 Torr of He, respectively. The experiments involved time‐resolved RF detection of the OH (A²Σ⁺ → X²Π transition at λ = 308 nm) following FP of H₂O/CH₃I/He mixtures. The OH(X²Π) radicals were produced by FP of H₂O in the vacuum‐UV at wavelengths λ > 115 nm using a commercial Perkin‐Elmer Xe flash lamp. Decays of OH in the presence of CH₃I are observed to be exponential, and the decay rates are found to be linearly dependent on the CH₃I concentration. The measured rate coefficients for the reaction of OH with CH₃I are described by the Arrhenius expression k_OH+CH3I = (4.1 ± 2.2) × 10^?12 exp [(?1240 ± 200)K/T] cm³ molecule^?1s^?1. The implications of the reported kinetic results for understanding the CH₃I chemistry of both atmospheric and nuclear industry interests are discussed. © 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: 547–556, 2011