Degradation of Reactive Blue 19 (RB19) by a Green Process Based on Peroxymonocarbonate Oxidation System.

The effectiveness of peroxymonocarbonate (HCO4 -) on the degradation of Reactive Blue 19 (RB19) textile dye was investigated in this study. The formation kinetics of HCO4 - produced in situ in a H2O2 - HCO3 - system was studied to control the experimental conditions for the investigation of RB19 degradation at mild conditions. The effects of metallic ion catalysts, the pH, the input HCO3 - and Co2+ concentrations, and UV irradiation were studied. The obtained result showed that Co2+ ion gave the highest efficiency on accelerating the rate of RB19 degradation by the H2O2-HCO3 - system. In the pH range of 7-10, the higher pH values resulted in faster dye degradation. The reaction orders of the RB19 degradation with respect to Co2+ and HCO3 - were determined to be 1.2 and 1.7, respectively. The UV irradiation remarkably enhanced the radical formation in the oxidation system, which led to high degradation efficiencies. The COD, TOC removal, and HPLC results clearly revealed complete mineralization of RB19 by the H2O2 - HCO3 --Co2+ system.

Determination of Sudan I and II in Food by High-Performance Liquid Chromatography after Simultaneous Adsorption on Nanosilica.

Analytical techniques for analyte quantification are often complex, time-consuming, and costly. Further, samples must be carefully prepared to make them suitable for each analytical technique, thus increasing complexity and cost and often requiring toxic solvents. In this paper, we propose a simple and quick method for the pre-concentration of analytes using a nonporous adsorbent: nanosilica, which is prepared from rice husks, an ecofriendly waste material. Subsequently, analysis using high-performance liquid chromatography with a photodiode array detector was used for accurate analyte quantification. To test our method, Sudan I and II dyes were selected because these are potential carcinogens that are often used to adulterate foods because of their bright colors. Although nanosilica has been used as an adsorbent before, the adsorption of hydrophobic organic dyes has not been investigated to date. Thus, the optimal conditions for dye adsorption on nanosilica were systematically studied and found to be 1 mM KCl, pH 3.0, and an adsorption time of 120 min, and the maximum adsorption capacities of the nanosilica for Sudan I and II were 0.619 and 0.699 mg·g-1, respectively. The adsorption of the dyes on the nanosilica is discussed in detail with respect to the surface area, functional groups, zeta potential, and adsorption isotherms. Under optimal conditions, the extraction efficiencies of Sudan I and Sudan II reached 98.3% and 92.8%, respectively, and the proposed method was applied for the analysis of several foods and achieved high recoveries (80-100%).

Crystal structures of three 4-substituted-2,2'-bipyridines synthesized by Sonogashira and Suzuki-Miyaura cross-coupling reactions.

Facile synthetic routes for three 4-substituted 2,2'-bi-pyridine derivatives, 4-[2-(4-methyl-phenyl)-ethyn-yl]-2,2'-bi-pyridine, C19H14N2, (I), 4-[2-(pyridin-3-yl)ethyn-yl]-2,2'-bi-pyridine, C17H11N3, (II), and 4-(indol-4-yl)-2,2'-bi-pyridine, C18H13N3, (III), via Sonogashira and Suzuki-Miyaura cross-coupling reactions, respect-ively, are described. As indicated by X-ray analysis, the 2,2'-bi-pyridine core, the ethyl-ene linkage and the substituents of (I) and (II) are almost planar [dihedral angles between the two ring systems: 8.98 (5) and 9.90 (6)° for the two mol-ecules of (I) in the asymmetric unit and 2.66 (14)° for (II)], allowing π-conjugation. On the contrary, in (III), the indole substituent ring is rotated significantly out of the bi-pyridine plane [dihedral angle = 55.82 (3)°], due to steric hindrance. The crystal packings of (I) and (II) are dominated by π-π inter-actions, resulting in layers of mol-ecules parallel to (30-2) in (I) and columns of mol-ecules along the a axis in (II). The packing of (III) exhibits zigzag chains of mol-ecules along the c axis inter-acting through N-H⋯N hydrogen bonds and π-π inter-actions. The contributions of unknown disordered solvent mol-ecules to the diffraction intensities in (II) were removed with the SQUEEZE [Spek (2015 ▸). Acta Cryst. C71, 9-18] algorithm of PLATON. The given chemical formula and other crystal data do not take into account these solvent mol-ecules.

Crystal structures of organoplatinum complexes containing alkyl-eugenoxyacetate and p-chloro-aniline.

In the title complexes, trans-di-chlorido-(4-chloro-aniline-κN){3-meth-oxy-4-meth-oxy-carbonyl-meth-oxy-1-[(2,3-η)-prop-2-en-1-yl]benzene}-platinum(II) 0.1-hydrate, [PtCl2(C6H6ClN)(C13H16O4)]·0.1H2O, (I), and trans-di-chlorido-(4-chloro-aniline-κN){4-eth-oxy-carbonyl-meth-oxy-3-meth-oxy-1-[(2,3-η)-prop-2-en-1-yl]benzene}-platinum(II), [PtCl2(C6H6ClN)(C14H18O4)], (II), the Pt(II) metal atom displays a slightly distorted square-planar coordination geometry defined by the aniline N atom, two chloride anions (trans-positioned) and one ethyl-enic double bond. The least-squares planes through the two aromatic ring systems make an angle of 47.3 (3)° for (I) and 38.6 (2)° for (II). Both structures show disorder for the PtCl2 fragment, in the case of (I) even further extended towards the CH2-CH=CH2 ligand. An intra-molecular C-H⋯Cl hydrogen bond occurs in (I). In the crystal packing of (I), which is dominated by N-H⋯O and C-H⋯Cl inter-actions, a partially occupied water mol-ecule is observed on a twofold rotation axis with a refined site occupancy of 0.10 (1). A C-H⋯π inter-action is also present. In (II), inversion dimers form chains along the b-axis direction by N-H⋯O hydrogen bonds.

Crystal structure of hexa-aqua-nickel(II) bis{2-[(5,6-di-hy-droxy-3-sul-fon-ato-quino-lin-1-ium-7-yl)oxy]acetate} dihydrate.

The asymmetric unit of the title compound, [Ni(H2O)6](C11H8NO8S)2·2H2O, features a half-hexa-aqua-nickel(II) complex cation with the Ni(II) ion on an inversion center, one deprotonated 5,6-dihy-droxy-3-sulfoquinolin-7-yloxyacetic acid (QOH) molecule appearing in its zwitterionic form and one lattice water mol-ecule. The sulfonate group is disordered over two positions with occupancy factors of 0.655 (5) and 0.345 (5). The hexa-aqua-nickel(II) cation inter-acts through hydrogen bonding with eight QOH mol-ecules and two water mol-ecules. The six-membered rings of quinoline show π-π stacking [centroid-to-centroid distances of 3.679 (2) Šand 3.714 (2) Å].

Crystal structure of trans-di-chlorido-(4-nitro-aniline-κN (1))(piperidine-κN)platinum(II).

In the title complex, [PtCl2(C5H11N)(C6H6N2O2)], the Pt(II) metal atom displays a slightly distorted trans-PtN2Cl2 square-planar coordination geometry. The dihedral angle between the mean plane of the benzene and piperidine rings is 89.03 (3)°. In the crystal structure, inversion dimers are formed via N-H⋯Cl hydrogen-bond inter-actions, resulting in chains parallel to the [001] direction. The benzene rings within the chains show π-π stacking inter-actions [centroid-to-centroid distances of 3.801 (3) Å] and neighbouring chains inter-act via N-H⋯O hydrogen bonds.

Stacking patterns of thieno[3,2-b]thiophenes functionalized by sequential palladium-catalyzed Suzuki and Heck cross-coupling reactions.

The crystal structures of three 5-alkenyl-2-arylthieno[3,2-b]thiophenes, namely 3,6-dibromo-5-(4-tert-butylstyryl)-2-(naphthalen-1-yl)thieno[3,2-b]thiophene, C(28)H(22)Br(2)S(2), (I), 3,6-dibromo-5-(4-methylstyryl)-2-(naphthalen-1-yl)thieno[3,2-b]thiophene, C(25)H(16)Br(2)S(2), (II), and 3,6-dibromo-2-(4-tert-butylphenyl)-5-(4-methylstyryl)thieno[3,2-b]thiophene, C(25)H(22)Br(2)S(2), (III), have been determined in order to evaluate the geometry of the molecules. The π-conjugated system containing the thieno[3,2-b]thiophene skeleton, the ethylene bridge and the phenyl rings is almost planar. The aromatic ring directly attached to the thieno[3,2-b]thiophene moiety is not coplanar with the thieno[3,2-b]thiophene moiety itself due to steric hindrance of the bromo substituent. The crystal packings are characterized by π-π stacking [only for (II)] and C-Br...π interactions. The long axes of the molecules in (I) are oriented in two directions; for the two other structures the long axis is oriented in one direction only.

Crystal structure of chlorido-(piperidine-κN)(quinoline-2-carboxyl-ato-κ(2) N,O)platinum(II).

The title compound, [Pt(C10H6NO2)Cl(C5H11N)], crystallizes with one mol-ecule in the asymmetric unit. The Pt(II) cation has a slightly distorted square-planar coordination environment defined by a chloride anion, the quinoline N atom and a carboxyl-ate O atom of the bidentate quinaldate ligand and a piperidine N atom. An intra-molecular C-H⋯Cl hydrogen bond occurs. In the crystal, mol-ecules are stacked into columns along the c axis by the formation of N-H⋯Cl and C-H⋯O hydrogen bonds.

Hydrogen-bonded chains in three cis-dichloridoplatinum(II) complexes bearing piperidine and amine ligands.

The crystal structures of cis-dichlorido(ethylamine-κN)(piperidine-κN)platinum(II), [PtCl2(C2H7N)(C5H11N)], (I), cis-dichlorido(3-methoxyaniline-κN)(piperidine-κN)platinum(II), [PtCl2(C5H11N)(C7H9NO)], (II), and cis-dichlorido(piperidine-κN)(quinoline-κN)platinum(II), [PtCl2(C5H11N)(C9H7N)], (III), have been determined at 100 K in order to verify the influence of the nonpiperidine ligand on the geometry and crystal packing. The crystal packing is characterized by N-H...Cl hydrogen bonding, resulting in the formation of chains of molecules connected in a head-to-tail fashion. Hydrogen-bonding interactions play a major role in the packing of (I), where the chains further aggregate into planes, but less so in the case of (II) and (III), where π-π stacking interactions are of greater importance.

Green-to-red photoconvertible Dronpa mutant for multimodal super-resolution fluorescence microscopy.

Advanced imaging techniques crucially depend on the labels used. In this work, we present the structure-guided design of a fluorescent protein that displays both reversibly photochromic and green-to-red photoconversion behavior. We first designed ffDronpa, a mutant of the photochromic fluorescent protein Dronpa that matures up to three times faster while retaining its interesting photochromic features. Using a combined evolutionary and structure-driven rational design strategy, we developed a green-to-red photoconvertible ffDronpa mutant, called pcDronpa, and explored different optimization strategies that resulted in its improved version, pcDronpa2. This fluorescent probe combines a high brightness with low photobleaching and photoblinking. We herein show that, despite its tetrameric nature, pcDronpa2 allows for multimodal subdiffraction imaging by sequentially imaging a given sample using both super-resolution fluctuation imaging and localization microscopy.

Improving the second-order nonlinear optical response of fluorescent proteins: the symmetry argument.

We have successfully designed and expressed a new fluorescent protein with improved second-order nonlinear optical properties. It is the first time that a fluorescent protein has been rationally altered for this particular characteristic. On the basis of the specific noncentrosymmetry requirements for second-order nonlinear optical effects, we had hypothesized that the surprisingly low first hyperpolarizability (ß) of the enhanced yellow fluorescent protein (eYFP) could be explained by centrosymmetric stacking of the chromophoric Tyr66 and the neighboring Tyr203 residue. The inversion center was removed by mutating Tyr203 into Phe203, with minor changes in the linear optical properties and even an improved fluorescence quantum yield. Structure determination by X-ray crystallography as well as linear optical characterization corroborate a correct folding and maturation. Measurement of ß by means of hyper-Rayleigh scattering (HRS) as well as their analysis using quantum chemistry calculations validate our hypothesis. This observation can eventually lead to improved red fluorescent proteins for even better performance. On the basis of the specific function (second-harmonic generation), the color of its emission, and in analogy with the "fruit" names, we propose SHardonnay as the name for this Tyr203Phe mutant of eYFP.

Structural basis for the influence of a single mutation K145N on the oligomerization and photoswitching rate of Dronpa.

The crystal structure of the on-state of PDM1-4, a single-mutation variant of the photochromic fluorescent protein Dronpa, is reported at 1.95 Å resolution. PDM1-4 is a Dronpa variant that possesses a slower off-switching rate than Dronpa and thus can effectively increase the image resolution in subdiffraction optical microscopy, although the precise molecular basis for this change has not been elucidated. This work shows that the Lys145Asn mutation in PDM1-4 stabilizes the interface available for dimerization, facilitating oligomerization of the protein. No significant changes were observed in the chromophore environment of PDM1-4 compared with Dronpa, and the ensemble absorption and emission properties of PDM1-4 were highly similar to those of Dronpa. It is proposed that the slower off-switching rate in PDM1-4 is caused by a decrease in the potential flexibility of certain ß-strands caused by oligomerization along the AC interface.