Search

In this work two positional-isomeric oxadiazol-pyridine ligands 3-(5-methyl-1,3,4-oxadiazol-2-yl)pyridine (L1) and 4-(5-methyl-1,3,4-oxadiazol-2-yl)pyridine (L2) have been designed and synthesized. A series of novel coordination polymers, namely [Cd2(μ2-L1)2(μ2-NCS)4]n (1), {[Cd(L1)(μ2-dca)2(H2O)]·H2O}n (2), {[Cu(μ2-L1)2(NCS)2]·0.5H2O}n (3), {[Ag2(μ2-L1)(μ3-L1)2]·2PF6}n (4), {[Ag3(μ2-L1)4(μ2-CF3SO3)(CF3SO3)]·CF3SO3} (5), {[Cd(L2)2(μ2-NCS)2]}n (6), [Ag(μ2-L2)(μ2-CF3SO3)]n (7) and {[Ag(μ2-L2)]·BF4}n (8) have been isolated. Both 1 and 2 are 2D CdII coordination polymers containing infinite {Cd–NCS–Cd} chains (for 1) or infinite {Cd–dca–Cd} layers (for 2), respectively. 3 is a 2D CuII coordination polymer, in which central metal ions are bridged via a bidentate bridging L1 ligand. While when different AgI salts were introduced into the reaction system, 1D AgI coordination polymers 4 and 5 with diverse coordination modes can be isolated. Furthermore, when the isomeric oxadiazol-pyridine L2 is used to replace L1 in the reaction system, 6–8 can be isolated. 6 is a 2D CdII coordination polymer containing {Cd–NCS–Cd} layers. 7 is a 2D neutral AgI coordination polymer while 8 is a 2D cationic AgI coordination polymer. Variable temperature magnetic susceptibility measurements (2–300 K) reveal anti-ferromagnetic interactions between central copper(II) ions for 3. Solid-state luminescent properties of 1, 2 and 4–8 have been investigated indicating strong fluorescent emissions. Additionally, luminescent measurements illustrate that complex 8 exhibits highly sensitive luminescence sensing for Cr2O72− ions in aqueous solutions with high quenching efficiency Ksv = 2.08 × 104 L mol−1 and low detection limit (0.19 μM (S/N = 3)). 8 also represents the first report of a coordination polymer based on oxadiazol-pyridine derivatives with a luminescence response to Cr2O72− anion pollutants in aqueous solutions.

Fifty-five soil samples were collected across the central and eastern Qinghai-Tibetan Plateau during July to August in 2013. These were analyzed for the sixteen polycyclic aromatic hydrocarbons (PAHs) called out by the USA EPA. The concentration characteristics, sources, and potential ecological risk assessment of the sixteen PAHs in the soils were investigated. The soils were extracted by ultrasonic extraction, purified by an HLB solid-phase extraction column, and quantified by gas chromatography-mass spectrometry (GC-MS). The total PAH concentrations ranged from 40.47 to 1276.40 μg·kg

Using the 4-substituted-1,2,4-triazole derivate ligand 4-p-tolyl-1,2,4-triazole (L), two novel luminescent Cadmium(II) frameworks, namely {[Cd(μ2-L)3]·(NO3)2·L}n (1) and [Cd1.5(μ2-L)(μ2-Br)2(μ3-Br)]n (2) have been isolated under hydrothermal conditions. The structural analysis reveals that 1 presents a one-dimensional (1D) chain structural motif containing novel infinite triple Cd-(trz)-Cd bridges (triply trz-bridged M–M species). While 2 presents a rare I2O0 type framework, in which the infinite 2D Cd–Br–Cd inorganic connectivity with a 4-connected Kagome topology can be observed. The FT-IR, PXRD and thermal stabilities of 1–2 have investigated. The solid-state photo-luminescent spectra of organic ligand L and 1–2 also have been measured indicating strong emission bands.

In this work two new multi-dentate 1,2,4-triazole derivate ligands 4-(4-methyl-2-pyridine)-1,2,4-triazole (L1), 4-(5-methyl-3-pyridine)-1,2,4-triazole (L2) have been designed and synthesized. Three novel cluster-based cationic silver(I) coordination compounds with L1 and L2, namely [Ag2(H2O)4(L1)2](CF3CO2)2 (1), [Ag4(L1)6](BF4)4 (2) and {[Ag2(H2O)(L2)2]·(BF4)2}n (3) have been isolated. When L1 and different Ag(I) salts are used, the bi-nuclear Ag(I) cluster 1 and the tetra-nuclear Ag(I) cluster 2 can be isolated indicating anion induced structural diversity. Further when L2 is used, 3 can be isolated. 3 is a 2D clustered-based coordination compound based on bi-nuclear Ag(I) clusters. PXRD patterns and solid state luminescent properties of 1–3 have been investigated. Further anion exchange properties 2 and 3 also have been investigated. 2 and 3 present novel examples of triazole–silver(I) coordination compounds for effectively capturing the anion pollutants Cr2O72−, MnO4− in water solutions and Congo Red in methanol solutions through the anion exchange process.

In this work, a flexible multi-dentate trans-4,4′-azo-1,2,4-triazole (atrz) ligand has been employed, and a series of novel coordination polymers, namely [Fe(μ-atrz)(NCS)2(H2O)2]n (1), [Fe(μ-atrz)(NCS)2(H2O)2]n (2), {[Fe(μ-atrz)(μ-Cl)(H2O)2]·Cl·H2O}n (3), {[Fe(μ-atrz)(atrz)2(H2O)2]·2Br·4H2O}n (4), {[Fe(μ-atrz)(atrz)2(H2O)2]·(BF4)2·2H2O}n (5), {[Cu(μ-atrz)3]·(BF4)2·2H2O}n (6), {[Cu(μ-atrz)3]·(BF4)2}n (7), {[Cu2(μ4-atrz)(μ2-OH)2(H2O)4]·SO4·3.75H2O}n (8), {[Zn(μ-atrz)(NCS)2]·0.5H2O}n (9) and {[Zn(μ-atrz)(NCS)2]}n (10) have been isolated. 1 and 2 present one-dimensional (1D) polymorphic iron(II)–triazole frameworks, in which bicycle-pedal motion of the azo moieties of atrz can be observed. Further, when different iron(II) salts are used, 1D iron(II)–triazole frameworks 3–5 with different 1D bridging motifs can be isolated. 6 has a 3D nano-porous CuII framework with dimensions of 11.709(1) A × 12.201(1) A. Interestingly, 6 exhibits guest induced single-crystal-to-single-crystal (SC-SC) structural transformation to obtain another 3D nano-porous CuII framework 7 with dimensions of 11.621(6) A × 16.674(1) A. 8 has a 2D cationic CuII framework constructed with infinite (CuO)n chains and unique μ4-bridging atrz ligands. Anion exchange experiment indicates an anion-induced structural transformation from the 3D CuII framework 6 to the 2D CuII framework 8 confirmed by PXRD patterns. Further, when Zn(NCS)2 is used in the reaction system, 9 can be isolated which exhibits guest induced SC-SC transformation to obtain 10 accompanied by a color change from red (9) to pale pink (10). Variable temperature magnetic susceptibility measurements (2–300 K) reveal anti-ferromagnetic interactions between central iron(II) ions for 1–5. The polymorphic iron(II) frameworks, guest induced single-crystal-to-single-crystal transformation and solvatochromism also reveal great potential for the construction of flexible frameworks employing 4,4′-azo-1,2,4-triazole as basic building blocks.

In this work a new flexible multi-dentate 1-(4-aminobenzyl)-1,2,4-triazole (abtz) ligand has been designed and synthesized, and a series of two-dimensional (2D) triazole-functionalized metal–organic frameworks, namely {[Cd(abtz)2(H2O)2]·(ClO4)2·H2O}n (1), {[Cd(abtz)2(H2O)2]·(SiF6)}n (2), {[Cd(abtz)2(H2O)2]·(ClO4)1.64·(HSO4)0.36·1.36H2O}n (3), {[Cd(abtz)2(NCS)]·(ClO4)}n (4) and {[Ag2(μ2-abtz) (μ3-abtz)(ClO4)]·(ClO4)}n (5) have been isolated. Firstly, when abtz and corresponding cadmium(II) salts are employed, new rectangular-grid 2D coordination frameworks containing free ClO4− or SiF62− anions, {[Cd(abtz)2(H2O)2]·(ClO4)2·H2O}n (1) and{[Cd(abtz)2(H2O)2]·(SiF6)}n (2), can be isolated. Furthermore, in 1 weakly H-bonded ClO4− anions present within the voids can be partly exchanged by HSO4− anions to generate the anion exchanged crystalline product {[Cd(abtz)2(H2O)2]·(ClO4)1.64·(HSO4)0.36·1.36H2O}n (3) in single-crystal-to-single-crystal (SC–SC) manner. On the other hand, 1 can be used as a precursor to react with NH4NCS to obtain the 2D bilayer framework {[Cd(abtz)2(NCS)]·(ClO4)}n (4) under hydrothermal conditions. This also presents a novel example of structural transformation with bond rupture/formation from a mono-layer framework 1 to a 2D bi-layer framework 4. Furthermore, when AgClO4 is used to replace Cd(ClO4)2 in the reaction system, another 2D layer framework {[Ag2(μ2-abtz)(μ3-abtz) (ClO4)]·(ClO4)}n (5) with unique (2,4,5) connected topology can be isolated. The solid state luminescence properties and PXRD patterns of 1–5 have been investigated. Additionally, luminescence measurements illustrate that complexes 4 and 5 represent novel examples as luminescent probes of new sensing materials. 4 shows highly sensitive response to acetone and Fe3+. Besides, 5 is the first report of multidimensional polymers based on triazole derivatives with luminescent response to small biological molecules such as vitamin C in water solutions.

Using a highly flexible ligand 1,2-bis(1,2,4-triazole-1-yl)ethane (L), the one-dimensional (1D) chain polymer [[Mn(L)(Cl)2(H2O)2]n (I) has been synthesized and structurally characterized. The crystal crystallizes in the monoclinic system, space group C2/c, a = 12.507(4), b = 8.812(3), c = 12.662(4) A, β = 115.474(6)°, Z = 4. The X-ray analysis shows that I has the three-dimensional (3D) supramolecular network featuring 1D channel along the crystallographic y axis via intermolecular O-H...N interactions.

In order to understand the pollution situation, as well as seasonal changes in characteristics and speciation of dissolved heavy metals in acid rain control zone, the concentrations of dissolved heavy metals in rainwater collected at Guiyang were measured using inductively coupled plasma mass spectrometry (ICP-MS). And the speciation of dissolved heavy metals was further simulated by PHREEQC model. The results showed that the dissolved Co, Ni, Cu, Zn and Cd concentrations were low and not higher than the national standards for drinking water quality in China. The dissolved Pd concentrations were high in fall and winter and higher than the national standards for drinking water quality in China. The Co and Ni in rainwater mainly came from the crust and there was almost no human impact. The Cu, Zn, Cd and Pd pollutions in rainwater were affected by human activity with different levels. The degrees of contamination in autumn and winter were more serious than those in spring and summer. The free metal ion species was the dominant form of dissolved heavy metal, accounting for 47.27%-95.28% of the dissolved metal in rainwater from Guiyang city. The free metal ion species was followed in abundance by Metal-Oxalate and Metal-sulfate complexes that accounted for 0.72% -51.87% and 0.50%-7.66%, respectively. The acidity of rainwater, acid type as well as content of ligand more likely controlled the distribution of dissolved heavy metal in precipitation.

Concentrations of metals, organic matter(OM), total nitrogen (TN) and total phosphorus (TP) were determined in sediment and soil samples collected from 15 selected sites along Dagu sewage discharge channel in Tianjin, China. Relative enrichment factors and correlation analysis were taken to study the distribution and pollution level of metals. The results show that pollution level is more serious in sediment than that in soil. Hg, Cd, Zn and Pb are more enriched while Cr, Ni and As are less enriched. Relative enrichment factors (REF) of Hg, Cd, Zn and Pb in sediment are 59.3, 25.4, 14.5 and 7.5, and that in soil are 8.44, 5.19, 6.6 and 3.3, respectively. The heavy metal concentrations greatly vary among different sampling sites, which is demonstrated by the fact that coefficient of variation (CV) varies from 74.4% to 110.8% in sediment. The highest enrichments of heavy metals are found in sampling site S4 and S12, which are affected by chemical industry wastewater. There is no significant correlation between metal concentrations in sediment and those in soil. The concentrations of heavy metals in sediment are not reciprocally correlated, either. However, significant correlations exist among many pollutants in soil. Hg, Cd, Zn and Pb are positively correlated with each other, at the same time they are positively correlated with OM, TN and TP, but Cr, Ni and As are poorly correlated with OM and TP, which suggests that Cd, Zn and Pb have similar environmental geochemical properties and are contaminated by anthropogenic impact. When compared with the main rivers in Tianjin, the enrichment of heavy metals in Dagu sewage discharge channel is relatively high.

Variations of delta 13C(org) and delta 15N values, C/N ratios, TOC and TN contents in Chaohu Lake sediments reflect the sources of organic matter in lake sediments, evolution of lake productivity and the eutrophic status in Chaohu Lake during last 100 years. Our results suggest that the sedimentary organic matter was derived mainly from aquatic algae and partly from land matter. However, the input of the pollutants from city and agriculture into the lake could not be neglected. Two stages can be found in the sediments cores according to the profiles of delta 13C(org), delta 15N values, TOC and TN contents. Below 10cm, delta 13C(org) values vary between - 21.74 per thousand and - 19.34 per thousand. Nitrogen fixing and non-nitrogen fixing phytoplankton coexist together. Two cores show different nutrition processes. Above 10cm, in both profiles, the values of delta 13C(org) start to decrease sharply, but delta 15N, TOC and TN increase. The construction of Chaohu Gate leads to the enhancement of lake productivity and development of eutrophication.

In this work the multi-dentate 4-amino-benzene-1,2,4-triazole (L1) ligand is used. A series of novel cluster-based micro-porous luminescent cadmium(II) frameworks, namely [Cd3(μ3-L1)2(μ2-L1)2(μ2-Cl)2Cl4]n (1), {[Cd2(μ3-L1)2(μ2-Br)2Br2]·1.05H2O}n (2) and {[Cd2(μ2-L1)3(L1)2(μ2-I)2]·(CdI4)·1.5H2O}n (3) have been isolated under hydrothermal conditions. 1 presents a 4-connected (4,4) topology using trinuclear Cd(II) clusters as basic nodes. For 1, two bridging μ2-Cl− anions and two bridging μ3-L1 ligands connect three neighboring CdII ions forming trinuclear Cd3 clusters. Each Cd3 cluster links four neighboring Cd3 clusters forming a 2D (two-dimensional) neutral micro-porous framework. 1D rhombic channels with dimensions of 7.594(2) A × 21.250(6) A can be observed along the c-axis. 2 presents a rare I1O3 hybrid type micro-porous framework. In 2 these bridging μ3-L1 ligands link central CdII ions forming a 3D Cd–L1 organic connectivity. Two kinds of 1D Cd–Br–Cd inorganic connectivities further consolidate the 3D Cd–L1 organic connectivity, which ultimately forms a rare I1O3 type hybrid framework. 3 presents a novel 3D cluster-based micro-porous cation framework containing 1D channels, in which guest CdI42− anions and water molecules are located. Topological analysis indicates that 3 presents a novel 4-connected dmp topology using binuclear Cd2I2 clusters as basic nodes. PXRD, TGA and Gas absorption experiments for 1–3 have also been carried out. Solid state photo-luminescent spectra of 1–3 have been determined indicating strong emission bands. For 1 selective photo-luminescent quenching for NO2− anions can be observed. The result also reveals that L1 can adopt various different coordinated modes and flexible spatial distortion dihedral angles (between aromatic benzene and triazole rings), which has great potential in the construction of these novel cluster-based micro-porous coordination frameworks.