UiO-66 Selective Enrichment Integrated with Thermal Desorption GC-MS for Detection of Benzene Homologues in Ambient Air.

In this study, UiO-66 was selected as sorbent media packed in the tube to selectively enrich trace levels of benzene homologues such as benzene, toluene, and xylene (BTX) in ambient air prior to thermal desorption (TD)-GC-MS determination. A series of experiments were conducted to obtain the optimal TD conditions. The results indicated that the optimal TD parameters were as follows: desorption temperature of 180°C, desorption flow rate of 50 mL min-1, and desorption time of 30 min. Furthermore, the method based on UiO-66 enrichment integrated with TD-GC-MS for trace levels of BTX was successfully developed. It exhibited a good linearity (R 2 > 0.99) in the range of 50-1000 ng, except for p, m-xylene in the range of 100-2000 ng, and achieved the recovery of 69.4-101.3%, and the relative standard deviation of 3.8-6.4%. The detection limits of BTX were 1.6-4.0 ng; according to 10 L of sampling volume, the method detection limits would be in the range of 0.16-0.40 µg m-3. Additionally, the method was successfully applied to determine BTX in indoor air and showed good selectivity and sensitivity. In summary, the findings in this work revealed that UiO-66 was an attractive adsorbent for selective enrichment trace levels of BTX compounds in ambient air, which was favorable for the subsequent detection by TD-GC-MS.

Embedment of Ag(I)-organic frameworks into silica gels for microextraction of polybrominated diphenyl ethers in soils.

Three Ag(I)-organic frameworks, [Ag5(pydc)2(CN)]n, {[Ag4(pydc)2]CH3CN}n, and [Ag(4,4'-bpy)NO3]n, were synthesized and embedded into silica gels to form metal-organic-framework (MOF)-embedded gels for the microextraction of polybrominated diphenyl ethers (PBDEs) in soils. Despite the great differences in the structures of the organic ligands, all three Ag(I)-organic frameworks were found to effectively accumulate and concentrate PBDEs from sample solutions prepared with contaminated soil and purified water, indicating the important roles of Ag centers in PBDE extraction. Under the optimal experimental conditions (MOF mass, water volume, temperature, extraction time, and back-extraction time) for PBDE extraction from sample solutions, the detection limits of seven PBDEs (BDE-28, 47, 99, 100, 153, 154, and 183) ranged from 0.01 to 2.6ngg(-1) for [Ag5(pydc)2(CN)]n, 0.20-0.64ngg(-1) for {[Ag4(pydc)2]CH3CN}n, and 0.60-3.08ngg(-1) for [Ag(4,4'-bpy)NO3]n. The reproducibilities of the three methods were all satisfactory with relative standard deviations (RSDs) in the range of 2.2-9.6%, 5.3-10.4%, and 6.9-9.4% for [Ag5(pydc)2(CN)]n, {[Ag4(pydc)2]CH3CN}n, and [Ag(4,4'-bpy)NO3]n, respectively. The use of Ag(I)-organic frameworks for the microextraction of PBDEs was validated using both certified reference soils and field-contaminated soils, and the proposed methods are recommended as rapid and environmentally friendly alternatives for the extraction and determination of PBDEs in soils.

catena-Poly[[di-chlorido-mercury(II)]-µ-1,4-bis-[2-(pyridin-4-yl)ethyn-yl]benzene-κ(2) N:N'].

In the polymeric title compound, [HgCl2(C20H12N2)] n , the Hg(II) atom is located on a twofold rotation axis and the benzene ring of the bidentate bridging 1,4-bis-[2-(pyridin-4-yl)ethyn-yl]benzene (L) ligand is located about a twofold rotation axis. The Hg(II) atom is coordinated by two N atoms of two different L ligands and by two chloride ions in a distorted tetra-hedral geometry. The dihedral angle between the coordinating pyridine and the benzene ring is 12.8 (2)°. The result of the bridging is the formation of a zigzag chain running parallel to [102]. The chains pack with no specific inter-molecular inter-actions between them.

Application of portable gas chromatography-photo ionization detector combined with headspace sampling for field analysis of benzene, toluene, ethylbenzene, and xylene in soils.

A method based on headspace (HS) sampling coupling with portable gas chromatography (GC) with photo ionization detector (PID) was developed for rapid determination of benzene, toluene, ethylbenzene, and xylenes (BTEX) in soils. Optimal conditions for HS gas sampling procedure were determined, and the influence of soil organic matter on the recovery of BTEX from soil was investigated using five representative Chinese soils. The results showed that the HS-portable-GC-PID method could be effectively operated at ambient temperature, and the addition of 15 ml of saturated NaCl solution in a 40-ml sampling vial and 60 s of shaking time for sample solution were optimum for the HS gas sampling procedure. The recoveries of each BTEX in soils ranged from 87.2 to 105.1 %, with relative standard deviations varying from 5.3 to 7.8 %. Good linearity was obtained for all BTEX compounds, and the detection limits were in the 0.1 to 0.8 µg kg(-1) range. Soil organic matter was identified as one of the principal elements that affect the HS gas sampling of BTEX in soils. The HS-portable-GC-PID method was successfully applied for field determination of benzene and toluene in soils of a former chemical plant in Jilin City, northeast China. Considering its satisfactory repeatability and reproducibility and particular suitability to be operated in ambient environment, HS sampling coupling with portable GC-PID is, therefore, recommended to be a suitable screening tool for rapid on-site determination of BTEX in soils.

The use of copper(II) isonicotinate-based micro-solid-phase extraction for the analysis of polybrominated diphenyl ethers in soils.

A micro-solid-phase extraction (µ-SPE) device was developed by filling copper(II) isonicotinate coordination polymer (Cu(4-C(5)H(4)N-COO)(2)(H(2)O)(4)) into a porous polypropylene envelope, and the µ-SPE, coupling with gas chromatography (GC) with a micro-cell electron capture detector (µ-ECD), was used for extraction and determination of PBDEs in soils. Variables affecting extraction procedures, including temperature, water volume, extraction time, and desorption time, were investigated in a spiked soil, and the parameters were optimized. Under the optimal experimental conditions, the method detection limits for seven PBDEs (BDE-28, 47, 99, 100, 153, 154, and 183) were in the range of 0.026-0.066 ng g(-1), and the reproducibility was satisfactory with the relative standard deviation in range of 1.3-10.1%. Good linear relationship between PBDEs concentrations and GC signals (defined as peak area) was obtained in the range between 0.1 and 200 ng g(-1). The recovery of the seven PBDEs by µ-SPE varied from 70 to 90%, which was comparable to that determined by accelerated solvent extraction method. Finally, the proposed method was used to determine PBDEs in several field-contaminated soils, and it was suggested that the µ-SPE is a promising alternative microextraction technique for the detection of PBDEs in soils.

Tetra-aqua-{5-[(pyridin-2-yl-methyl-idene)amino]benzene-1,3-dicarboxyl-ato-κ(2)N,N'}nickel(II) tetra-hydrate.

The title structure, [Ni(C(14)H(8)N(2)O(4))(H(2)O)(4)]·4H(2)O, contains a mononuclear Ni(II) complex formed by a chelating bidentate Schiff base and by four Ni-bonded water mol-ecules. The Ni(II) atom is in a distorted octa-hedral coordination by two N atoms in a cis disposition [Ni-N = 2.0753 (16) and 2.1048 (16) Å] and by four water O atoms [Ni-O = 2.0500 (15)-2.0822 (15) Å]. The crystal structure is completed by four further non-coordinating water mol-ecules and all constituents are linked in a three-dimensional manner by an extensive system of 16 O-H⋯O hydrogen bonds.

Diaqua-bis-(2-oxo-2H-chromene-3-carboxyl-ato-κO,O)manganese(II).

In the title compound, [Mn(C(10)H(5)O(4))(2)(H(2)O)(2)], the Mn(II) atom lies on a crystallographic inversion center and is six-coordinated by two O atoms from water mol-ecules in the axial positions and four O atoms from two deprotonated coumarin-3-carb-oxy-lic acid ligands in the equatorial plane. The overall coordination geometry is slightly distorted octa-hedral. The Mn-O bond distances vary between 2.0931 (12) and 2.2315 (13) Å. O-H⋯O hydrogen bonds between the H atoms of coordinated water mol-ecules and the O atoms of the carboxyl-ate groups link the complex mol-ecules into two-dimensional layers parallel to the ab plane.

Diaqua-bis-(2-oxo-2H-chromene-3-carboxyl-ato)copper(II).

In the title compound, [Cu(C(10)H(5)O(4))(2)(H(2)O)(2)], the Cu(II) atom lies on a crystallographic inversion center and exhibits an octa-hedral coordination defined by two O atoms from water mol-ecules in the axial positions and by four O atoms from two deprotonated coumarin-3-carb-oxy-lic acid ligands in the equatorial positions. The angles around the Cu(II) atom vary between 85.32 (6) and 94.68 (6)°. The Cu-O bond distances between the Cu(II) atom and the O atoms vary between 1.9424 (14) and 2.3229 (15) Å. The layers inter-digitate via face-to-face aromatic inter-actions [3.6490 (8) Å] between coumarin moieties such that the inter-layer separation is 10.460 (2) Å, i.e. the length of the c axis. O-H⋯O hydrogen bonds between the H atoms of coordinated water mol-ecules and the O atoms of carboxyl-ate groups link the complex mol-ecules into layers parallel to the ab plane.

[µ(2)-Bis(diphenyl-phosphanyl)methane][µ(3)-bis-(diphenyl-phosphanyl)meth-yl]trichlorido-tetra-gold(I) tetra-hydro-furan disolvate.

The title tetra-nuclear complex, [Au(4)(C(25)H(21)P(2))Cl(3)(C(25)H(22)P(2))]·2C(4)H(8)O, features two non-equivalent Ph(2)PCPPh(2) fragments, one of which represents the 'complete' mol-ecule (with two H atoms at the central C atom); each of the two P atoms of this mol-ecule is coordinated by an Au atom [Au-P = 2.2256 (13) and 2.2710 (13) Å], and these two Au atoms form an Au-Au bond [3.2945 (3) Å], thus closing the five-membered Au(2)P(2)C ring. The first of these Au atoms has a terminal chlorido ligand [Au-Cl = 2.2806 (12) Å], whereas the second Au atom forms a covalent bond with the central C atom of the bis-(diphenyl-phosphino)methyl group [Au-C = 2.114 (5) Å]; the latter group in turn coordinates with its P atoms the gold atoms of the Cl-Au-Au-Cl group [Au-P = 2.2356 (13) and 2.2338 (13), Au-Au = 3.3177 (3), Au-Cl = 2.3091 (12) and 2.2950 (13) Å], thus closing the second Au(2)P(2)C ring. The two such rings have different chemical functions, but both exhibit envelope conformations. However, the first (with different substituents at the Au atoms) is non-symmetrical with one of the P atoms in the flap position of the envelope; the other one has a conformation with mirror symmetry, and the gold-substituted C atom is displaced by 0.740 (5) Šfrom the almost exactly planar (r.m.s. deviation = 0.0038 Å) Au(2)P(2) group.

Diaqua-bis-(2-oxo-2H-chromene-3-carboxyl-ato-κO,O)cadmium.

In the title mononuclear cadmium complex, [Cd(C(10)H(5)O(4))(2)(H(2)O)(2)], the Cd(II) atom, located on a crystallographic inversion center, exhibits a slightly distorted octa-hedral geometry and is six-coordinated by two O atoms from water mol-ecules in the axial positions and four O atoms from two deprotonated coumarin-3-carb-oxy-lic acid ligands in the equatorial plane. Angles around the Cd(II) atom vary between 81.00 (5) and 99.00 (0)°. The Cd-O bond lengths vary between 2.1961 (13) and 2.3360 (13) Å. O-H⋯O hydrogen bonds between the H atoms of coordinated water mol-ecules and the O atoms of carboxyl-ate groups link the complex mol-ecules into layers parallel to the ab plane.

Diaqua-bis-(2-oxo-2H-chromene-3-carboxyl-ato)zinc(II).

In the title compound, [Zn(C(10)H(5)O(4))(2)(H(2)O)(2)], the Zn(II) atom lies on a crystallographic inversion center and is six-coordinated by two O atoms from water mol-ecules in the axial positions and four O atoms from two deprotonated coumarin-3-carb-oxy-late ligands in the equatorial plane, forming a slightly distorted octa-hedral coordination geometry. O-H⋯O hydrogen-bonding inter-actions involving the water mol-ecules form infinite chains parallel to [010].

Bis[µ-4-methyl-2-(2-pyridyl-methyl-sulfan-yl)pyrimidine-κN]bis-[(trifluoro-methanesulfonato-κO)silver(I)].

In the centrosymmetric dinuclear title complex, [Ag(2)(CF(3)SO(3))(2)(C(11)H(11)N(3)S)(2)], the Ag(I) atom is coordinated by two N atoms from two 4-methyl-2-(2-pyridyl-methyl-sulfan-yl)pyrimidine ligands and one O atom from a trifluoro-methane-sulfonate anion in a distorted T-type coordination geometry. The ligand adopts a bidentate bridging coordination mode through one pyridyl N atom and one pyrimidine N atom. In the crystal structure, π-π inter-actions are present between adjacent pyrimidine rings, with a centroid-to-centroid distance of 3.875 (7) Å.

Dimethyl 4,4'-(pyridine-2,6-diyl)dibenzoate.

The title mol-ecule, C(21)H(17)NO(4), reveals axial symmetry, with the pyridine N atom located on a crystallographic twofold axis. The mol-ecule is dish-shaped, with dihedral angles between the benzene and pyridine rings of 24.643 (1) and 24.797 (1)°, respectively. The -COO plane and the benzene ring are almost coplanar [dihedral angle = 5.286 (1)°].

2,2'-[Ethane-1,2-diylbis(sulfanedi-yl)]bis-(pyridine N-oxide).

The tile compound, C(12)H(12)N(2)O(2)S(2), lies on an inversion center. The two pyridyl rings are parallel to each other. The structure is devoid of any classical hydrogen bonds due to lack of appropriate donors and acceptors for such bonds. However, non-classical hydrogen bonds of the types C-H⋯O and C-H⋯S stabilize the structure.

Tetra-aqua-bis(3-carboxyl-atopyridine N-oxide-κO)cadmium(II).

In the title complex, [Cd(C(6)H(4)NO(3))(2)(H(2)O)(4)], the Cd(II) atom is situated on a crystallographic centre of inversion. The Cd(II) atom shows a slightly distorted octa-hedral geometry and is coordinated by four O atoms from water mol-ecules and two O atoms from deprotonated carboxyl groups of nicotinic acid N-oxide ligands. The mononuclear complex mol-ecules are linked by O-H⋯O hydrogen bonds, forming a three-dimensional network structure.

A one-dimensional cadmium(II) complex supported by a sulfur-nitro-gen mixed-donor ligand.

In the title compound, catena-poly[cadmium(II)-bis-(µ-5-am-ino-1,3,4-thia-diazole-2-thiol-ato)-κ(2)N(3):S(2);κ(2)S(2):N(3)], [Cd(C(2)H(2)N(3)S(2))(2)](n), the Cd(II) ion is coordinated by two N atoms of the 1,3,4-thia-diazole rings from two ligands and two S atoms of sulfhydryl from two other ligands in a slightly distorted tetra-hedral geometry. The ligands bridge Cd(II) ions, forming one-dimensional chains along [001], which are connected by N-H⋯N and N-H⋯S hydrogen bonds into a three-dimensional network.

2,2'-[o-Phenylenebis(methylenethio)]bis(pyridine N-oxide).

In the title compound, C(18)H(16)N(2)O(2)S(2), the benzene ring makes dihedral angles of 7.41 and 86.59° with the two outer pyridine N-oxygen rings. Two short intramolecular C-H⋯S contacts occur. The crystal packing is stabilized by C-H⋯O hydrogen bonds, C-H⋯π inter-actions and weak π-π staking inter-actions [centroid-centroid distance 3.7596 (7) Å].

Bis(5,6-dicarboxy-benzimidazolium) sulfate monohydrate.

In the title compound, 2C(9)H(7)N(2)O(4) (+)·SO(4) (2-)·H(2)O, the sulfate S atom and the water O atom reside on a crystallographic twofold axis. In the crystal, the component species are linked by N-H⋯O, O-H⋯O and C-H⋯O hydrogen bonds, forming a three-dimensional network structure. An intramol-ecular O-H⋯O link is seen in the cation.

Tetra-µ-acetato-bis-[(pyridine N-oxide)copper(II)](Cu-Cu).

The mol-ecule of the title binuclear copper(II) complex, [Cu(2)(CH(3)COO)(4)(C(5)H(5)NO)(2)], occupies a special position on a crystallographic inversion centre; the coordination environment of the Cu(II) atom is slightly distorted square-pyramidal and is made up of four O atoms belonging to four acetate groups in the basal plane with the O atom of pyridine N-oxide ligand in the apical position. The Cu-Cu distance is 2.6376 (6) Å.

catena-Poly[silver(I)-µ-pyrazolato-κN:N'].

The title compound, [Ag(C(3)H(3)N(2))](n), has an infinite helical chain structure in which each pyrazolate group bridges two Ag(I) atoms related by a 2(1) axis with an intra-chain Ag⋯Ag separation of 3.3718 (7) Å. Each Ag(I) center is linearly coordinated by two N atoms [N-Ag-N angle = 169.98 (14)°]. The chains are held together by inter-chain Ag⋯Ag inter-actions [3.2547 (6) Å], forming a two-dimensional layer. The X-ray single-crystal diffraction result is consonant with that of the ab initio X-ray powder diffraction reported by Masciocchi, Moret, Cairati, Sironi, Ardizzoia & La Monica [J. Am. Chem. Soc. (1994). 116, 7668-7676], with only minor deviations of structural parameters.