A butterfly shaped Eu4(OH)2 cluster-based luminescent metal-organic framework with Lewis basic triazole sites demonstrating turn off sensing in the presence of organic amines.

The effective detection of organic amines is particularly important for environmental protection and human health. Herein, according to hard and soft acid base theory, a novel three-dimensional (3D) butterfly shaped Eu4(OH)2 cluster-based metal-organic framework with Lewis basic triazole sites, {[Eu4(taip)4(ox)(OH)2(H2O)4]·3H2O}n (1) (H2taip = 5-(1,2,4-triazol-1-yl) isophthalic acid, H2ox = oxalic acid), was successfully synthesized under solvothermal conditions, and was characterized by single crystal X-ray diffraction, powder X-ray diffraction, elemental analysis, infrared spectroscopy and thermogravimetric analysis. Structural analysis reveals that compound 1 is a 3D net constructed from butterfly shaped Eu4(OH)2 clusters and contains isosceles triangular channels with dimensions of 8.84 × 8.84 × 8.63 Å3, which shows an unprecedented 8-connected topology with a Schläfli symbol {36·418·53·6}. Fluorescence experiments of compound 1 show sensitive luminescence quenching responses to organic amines such as diethylamine (DEA), trimethylamine (TMA), triethylamine (TEA), ethylenediamine (EDA) and aniline, and the quenching constants (KSV) decrease in the following order: EDA > DEA > TMA > TEA > aniline. The fluorescence quenching responses may be attributed to the energy gap between the LUMO energy values of H2taip and organic amines, which hinders the transfer of excited state energy to the emission state of Eu3+ and results in luminescence quenching. The fluorescence lifetimes of compound 1 in ethanol and organic anilines indicate that the fluorescence recognition process of organic amines was static.

Four new Cu6S6 cluster-based coordination compounds: synthesis, crystal structures and fluorescence properties.

A hexagonal prismatic Cu6S6 cluster exhibits excellent near-infrared fluorescence properties due to its short Cu-Cu bonds, however, the construction of Cu6S6 cluster-based compounds with extended structures is still a challenge. Here, four new Cu6S6 cluster-based coordination compounds, formulated as Cu3(pymt)3 (1), {(CuCN)2[Cu3(mpymt)3]}n (2), {(CuSCN)[Cu3(mpymt)3]}n (3) and {(CuCN)2[Cu3(dmpymt)3]·CH3CN}n (4) (Hpymt = pyrimidine-2-thiolate, Hmpymt = 4-methyl-pyrimidine-2-thione and Hdmpymt = 4,6-dimethylpyrimidine-2-thione), have been synthesized through the reactions of mercaptopyrimidine derivatives and CuCN or CuSCN under solvo-thermal conditions and characterized by single-crystal X-ray diffraction, powder X-ray diffraction, IR spectroscopy, elemental analysis, and thermal gravimetric analysis. Single-crystal X-ray diffraction analysis reveals that compound 1 is a zero-dimensional Cu6(pymt)6 molecule containing a distorted pseudo-hexagonal prismatic Cu6S6 core. Compounds 2 and 4 with isomorphic frameworks but different organic linkers show a rare three-dimensional framework with nor topology constructed from Cu6(mpymt)6 units and one-dimensional chiral [Cu(CN)]n chains; compared with compound 2, a more hydrophobic one-dimensional channel in compound 4 is observed due to the increase of the methyl groups on the pyrimidine ligand, in which acetonitrile molecules are filled in the channels of compound 4. Compound 3 shows a rare two-dimensional layer constructed from Cu6(mpymt)6 units and one-dimensional puckered (CuSCN)n chains. For the first time, Cu6S6 clusters are connected to one-dimensional inorganic CuCN (or CuSCN) chains through mercaptopyrimidine derivatives to obtain extended arrays in compounds 2-4. The crystals of compounds 1-4 in the solid state all show apparent red light emission. Compound 4 shows sensitive luminescence quenching response to nitrobenzene (NB), and the corresponding quenching constant (Ksv) and detection limit are 2.06 × 103 M-1 and 9.27 ppm, respectively. This study provides a new strategy to construct Cu6S6 cluster-based coordination polymers that have great potential in various applications such as luminescence sensing.

Improved NO2 Gas Sensing Properties of Graphene Oxide Reduced by Two-beam-laser Interference.

We report on the fabrication of a NO2 gas sensor from room-temperature reduction of graphene oxide(GO) via two-beam-laser interference (TBLI). The method of TBLI gives the distribution of periodic dissociation energies for oxygen functional groups, which are capable to reduce the graphene oxide to hierarchical graphene nanostructures, which holds great promise for gaseous molecular adsorption. The fabricated reduced graphene oxide(RGO) sensor enhanced sensing response in NO2 and accelerated response/recovery rates. It is seen that, for 20 ppm NO2, the response (Ra/Rg) of the sensor based on RGO hierarchical nanostructures is 1.27, which is higher than that of GO (1.06) and thermal reduced RGO (1.04). The response time and recovery time of the sensor based on laser reduced RGO are 10 s and 7 s, which are much shorter than those of GO (34 s and 45 s), indicating that the sensing performances for NO2 sensor at room temperature have been enhanced by introduction of nanostructures. This mask-free and large-area approach to the production of hierarchical graphene micro-nanostructures, could lead to the implementation of future graphene-based sensors.

Protective Effects of Blueberry Anthocyanins against H2O2-Induced Oxidative Injuries in Human Retinal Pigment Epithelial Cells.

Blueberry anthocyanins are considered protective of eye health because of their recognized antioxidant properties. In this study, blueberry anthocyanin extract (BAE), malvidin (Mv), malvidin-3-glucoside (Mv-3-glc), and malvidin-3-galactoside (Mv-3-gal) all reduced H2O2-induced oxidative stress by decreasing the levels of reactive oxygen species and malondialdehyde and increasing the levels of superoxide dismutase, catalase, and glutathione peroxidase in human retinal pigment epithelial cells. BAE and the anthocyanin standards enhanced cell viability from 63.69 ± 3.36 to 86.57 ± 6.92% (BAE), 115.72 ± 23.41% (Mv), 98.15 ± 9.39% (Mv-3-glc), and 127.97 ± 20.09% (Mv-3-gal) and significantly inhibited cell apoptosis (P < 0.01 for all). Mitogen-activated-protein-kinase pathways, including ERK1/2 and p38, were involved in the bioactivities. In addition, the anthocyanins decreased vascular-endothelial-cell-growth-factor levels and activated Akt-signal pathways. These combined results supported the hypothesis that blueberry anthocyanins could inhibit the induction and progression of age-related macular degeneration (AMD) through antioxidant mechanisms.

Thermal degradation kinetics of all-trans and cis-carotenoids in a light-induced model system.

Thermal degradation kinetics of lutein, zeaxanthin, ß-cryptoxanthin, ß-carotene was studied at 25, 35, and 45°C in a model system. Qualitative and quantitative analyses of all-trans- and cis-carotenoids were conducted using HPLC-DAD-MS technologies. Kinetic and thermodynamic parameters were calculated by non-linear regression. A total of 29 geometrical isomers and four oxidation products were detected, including all-trans-, keto compounds, mono-cis- and di-cis-isomers. Degradations of all-trans-lutein, zeaxanthin, ß-cryptoxanthin, and ß-carotene were described by a first-order kinetic model, with the order of rate constants as kß-carotene>kß-cryptoxanthin>klutein>kzeaxanthin. Activation energies of zeaxanthin, lutein, ß-cryptoxanthin, and ß-carotene were 65.6, 38.9, 33.9, and 8.6kJ/moL, respectively. cis-carotenoids also followed with the first-order kinetic model, but they did not show a defined sequence of degradation rate constants and activation energies at different temperatures. A possible degradation pathway of four carotenoids was identified to better understand the mechanism of carotenoid degradation.

Three novel Cu6S6 cluster-based coordination compounds: synthesis, framework modulation and the sensing of small molecules and Fe(3+) ions.

Three novel Cu6S6 cluster-based coordination compounds formulated as [Cu(mpymt)3]2 (1), {(CuBr4)[Cu(mpymt)6]}n (2), and {(CuI6)[Cu(mpymt)6]}n (3) (Hmpymt = 4-methylpyrimidine-2-thione), have been synthesized under solvothermal conditions and characterized by elemental analysis, infrared (IR) spectroscopy, thermal gravimetric analysis, powder X-ray diffraction and single-crystal X-ray diffraction. Structural analysis reveals that compound 1 shows a distorted octahedral core of six copper atoms (Cu6S6) constructed from four α and two ß type N[double bond, length as m-dash]C-SH parts from six mpymt(-) anions. Compound 2 displays an interesting 3D framework constructed from Cu6S6 and Cu4Br4 Cu(i) clusters simultaneously, interestingly, six mpymt(-) with α type N[double bond, length as m-dash]C-SH parts are involved in the formation of Cu6S6. Compound 3 displays an infinite 1D framework constructed from Cu6S6 and Cu6I6 Cu(i) clusters, notably, four α and two ß type N[double bond, length as m-dash]C-SH parts are involved in the formation of the Cu6S6 cluster, however, only mpymt(-) ligands containing α type N[double bond, length as m-dash]C-SH parts form the bridged Cu6I6 cluster. The experimental results reveal that halogen ions finely modulate the structural features of compounds 1-3. The fluorescent properties of compounds 1-3 in the solid state and in various solvent emulsions were investigated in detail, the results of which indicate that compounds 1-3 are all highly sensitive naked eye colorimetric sensors for NB, 2-NT and Fe(3+) (NB = nitrobenzene and 2-NT = 2-nitrotoluene).

A novel 3D Cu(I) coordination polymer based on Cu6Br2 and Cu2(CN)2 SBUs: in situ ligand formation and use as a naked-eye colorimetric sensor for NB and 2-NT.

A novel coordination polymer with the chemical formula [Cu4Br(CN)(mtz)2]n (mtz = 5-methyl tetrazole) (), has been synthesized under solvothermal conditions and characterized by elemental analysis, infrared (IR) spectroscopy, thermal gravimetric analysis, powder X-ray diffraction and single-crystal X-ray diffraction. Interestingly, the Cu(i), CN(-) and mtz(-) in compound are all generated from an in situ translation of the original precursors: Cu(2+), acetonitrile and 1-methyl-5-mercapto-1,2,3,4-tetrazole (Hmnt). The in situ ring-to-ring conversion of Hmnt into mtz(-) was found for the first time. Structural analysis reveals that compound is a novel 3D tetrazole-based Cu(i) coordination polymer, containing both metal halide cluster Cu6Br2 and metal pseudohalide cluster Cu2(CN)2 secondary building units (SBUs), which shows an unprecedented (3,6,10)-connected topology. Notably, a pseudo-porphyrin structure with 16-membered rings constructed by four mtz(-) anions and four copper(i) ions was observed in compound . The fluorescence properties of compound were investigated in the solid state and in various solvent emulsions, the results show that compound is a highly sensitive naked-eye colorimetric sensor for NB and 2-NT (NB = nitrobenzene and 2-NT = 2-nitrotoluene).

Effect of ultrasonic waves on the stability of all-trans lutein and its degradation kinetics.

Ultrasound treatment has been widely applied in the extraction of biologically active compounds including carotenoids. However, there are few reports on their effects on the stability of these compounds. In the present study, the stability of all-trans lutein, one of the carotenoids, was investigated under the action of ultrasound. Results showed that ultrasound induced the isomerization of all-trans lutein to its isomers, namely to 13-cis lutein, 13'-cis lutein, 9-cis lutein and 9'-cis lutein as analyzed by HPLC coupled with DAD and LC-MS; and the percentage of the isomerization increased with increasing both ultrasonic frequency and power. The stability of all-trans lutein in dichloromethane was worst among multiple kinds of solvents. Interestingly, the retention rate of all-trans lutein improved as the temperature increased, which runs counter to the Arrhenius law. Under ultrasound irradiation, the degradation mechanism might be different with various temperatures, the degradation of all-trans lutein followed first-order kinetics at 20°C, while second-order kinetics was followed at 30-50°C. As the ultrasonic reaction time prolonged, lutein epoxidation nearly occurred. Those results presented here emphasized that UAE techniques should be carefully used in the extraction of all-trans lutein.

Optimization of the ultrasound-assisted synthesis of lutein disuccinate using uniform design.

The ultrasound-assisted synthesis of lutein disuccinate from all-trans lutein (AL) and succinic anhydride (SA) was investigated in this study. Triethylamine was used as the catalyst. Based on the single-factor experiments, a 7-level-3-factor uniform design and response surface analysis were further employed to evaluate the effects of the selected variables including molar ratio of SA/AL, reaction time and ultrasonic power on the yield of lutein disuccinate. The results indicated that the data were adequately fitted into a second-order polynomial model; the molar ratio of SA/AL significantly affected the synthesis of lutein disuccinate, whereas reaction time and ultrasonic power did not. Based on ridge max analysis, the optimum condition for lutein disuccinate synthesis was predicted to be the molar ratio of SA/AL 265.3:1, ultrasonic power 300 W and reaction time 131.6 min with the lutein disuccinate yield of 80.53±0.18%, which give a 43.8% increase compared with the traditional method, and also significantly shorten the reaction time.

A heterometallic sandwich complex of europium(II) for luminescent studies.

A divalent europium complex [(L(Ph))(2)Eu{K(THF)(2)}(2)] (L(Ph) = Ph(2)Si(NAr)(2), Ar = 2,6-(i)Pr(2)C(6)H(3)) (THF = Tetrahydrofuran) (2), which has a sandwich structure with potassium-arene π interactions, was synthesized in high yield via a one-pot process. This complex has been fully characterized, and luminescent studies showed that the 528 nm emission peak can be attributed to the 4f-5d transition of Eu(2+).

Poly[bis-[µ(2)-1,4-bis-(1H-imidazol-1-yl)butane]-dichloridonickel(II)].

The asymmetric unit of the title compound, [NiCl(2)(C(10)H(14)N(4))(2)](n), consists of one Ni(2+) ion which is located on an inversion center, one 1,4-bis-(imidazol-1-yl)butane (bimb) and one chloride ion. The Ni(2+) ion exhibits a distorted octa-hedral coordination environment defined by four N atoms from four bimb ligands in the equatorial plane and two chloride ions in axial positions. The bridging coordination mode of the bimb ligands leads to the formation of inter-penetrating square Ni(4)(bimb)(4) units that are arranged parallel to (001). The separation between the Ni atoms in these units is 13.740 (3) Å.

(µ-5-Carb-oxy-1H-imidazole-4-carboxyl-ato-κN,O:N,O)bis-[amminesilver(I)].

In the title compound, [Ag(2)(C(5)H(2)N(2)O(4))(NH(3))(2)], each of the two Ag(I) atoms is coordinated by two N atoms from an ammonia mol-ecule and a 5-carb-oxy-1H-imidazole-4-carboxyl-ate ligand in an almost linear geometry, and by one carboxyl-ate O atom with a weak inter-action. The Ag atoms are assembled into a linear tetra-mer through Ag⋯Ag inter-actions. Each Ag tetra-mer is linked by four 5-carb-oxy-1H-imidazole-4-carboxyl-ate ligands, forming a puckered chain. The complex involves a strong intra-molecular O-H⋯O hydrogen bond.

4-Hydr-oxy-6-[(4-hydr-oxy-1-oxo-1,2-dihydro-phthalazin-6-yl)carbon-yl]phthalazin-1(2H)-one.

In the crystal structure of the title compound, C(17)H(10)N(4)O(5), the mol-ecules lie on twofold axes (through the ketone bridge C and O atoms). The dihedral angle between the two phthalazine rings is 52.25 (1)°. In the crystal, inter-molecular N-H⋯O and O-H⋯O inter-actions link the mol-ecules.

5,5'-Di-4-pyridyl-2,2'-(p-phenyl-ene)di-1,3,4-oxadiazole.

In the crystal structure of the title compound, C(20)H(12)N(6)O(2), the mol-ecules are located on centres of inversion. The complete mol-ecule is almost planar, with a maximum deviation from the mean plane of 0.0657 (1) Šfor the O atom. In the crystal, mol-ecules are stacked into columns elongated in the a axis direction. The centroid-centroid distances between the aromatic rings of the mol-ecules within the columns are 3.6406 (1) and 3.6287 (2) Å. Mol-ecules are additionally connected via weak inter-molecular C-H⋯N hydrogen bonding.

A new route for preparing coordination polymers from hydrothermal reactions involving in situ ligand synthesis.

The coordination chemistry of inorganic cobalt salt and the organic ligands H(4)bbh (=benzene-1,2,4,5-bihydrazide) and H(3)bcbh (=benzene-4-carboxylate-1,2-bihydrazide) generated through the in situ hydrothermal acylate reaction of H(4)bta (=benzene-1,2,4,5-tetracarboxylic acid) and H(3)btc (=benzene-1,2,4-tricarboxylic acid) with hydrazine hydrate, respectively, has been investigated. Three new coordination polymers were prepared and fully characterized by infrared spectroscopy, elemental analysis, and single-crystal X-ray diffraction. The compound [Co(micro(3)-H(2)bbh)(phen)](n)() (1) (triclinic space group P with a = 9.762(4) A, b = 10.169(4) A, c = 11.143(4) A, alpha = 80.96(3) degrees, beta = 64.49(3) degrees, gamma = 71.88(3) degrees, Z = 2) was synthesized from the reaction of CoCl(2).6H(2)O, H(4)bta (=benzene-1,2,4,5-tetracarboxylic acid), N(2)H(4).H(2)O, phen (=1,10-phenanthroline) and H(2)O, and consists of one-dimensional double-chains. [Co(micro(4)-H(2)bbh)(H(2)O)(2)](n)() (2) (monoclinic space group P2(1)/c with a = 6.8687(5) A, b = 7.5943(6) A, c = 10.0401(6) A, beta = 95.250(4) degrees, Z = 2) was generated by the combination of CoCl(2).6H(2)O, H(4)bta, N(2)H(4).H(2)O, and H(2)O. It adopts a three-dimensional structural motif in the solid state with channels consisting of 20-numbered rings. [Co(micro(3)-Hbcbh)(bpy)](n)() (3) (monoclinic space group Cc with a = 9.9464(13) A, b = 23.685(5) A, c = 7.9491 (16) A, beta = 117.677(13) degrees, Z = 4) was obtained from the mixture of CoCl(2).6H(2)O, N(2)H(4).H(2)O, H(3)btc (=benzene-1,2,4-tricarboxylic acid), bpy (=2,2'-dipyridyl), and H(2)O, and features a two-dimensional plane. The results of magnetic research indicate that there exist antiferromagnetic interactions between Co centers in both compounds 1 and 2.