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1.
Chem Commun (Camb) ; 2020 Sep 14.
Artigo em Inglês | MEDLINE | ID: mdl-32926022

RESUMO

Thermal-assisted spin crossover and field-induced slow magnetic relaxation coexist in the solid state for the mononuclear cobalt(ii) complex with the non-innocent 2,6-bis(N-4-methoxyphenylformimidoyl)pyridine ligand. One-electron oxidation of the paramagnetic low-spin CoII ion (SCo = 1/2) to the diamagnetic low-spin CoIII ion (SCo = 0) leads to the electroswitching of the slow magnetic relaxation in acetonitrile solution.

2.
Talanta ; 215: 120910, 2020 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-32312454

RESUMO

Chemical vapor deposition of MOFs (MOF-CVD) has been used to coat solid-phase microextraction (SPME) fibers with ZIF-8, by exposing ZnO layers to the linker vapor (2-methylimidazole). This ZIF-8 coating has been used as a seed layer in a following solvothermal MOF growth step in order to increase the ZIF-8 thickness. The combined MOF-CVD and solvothermal growth of ZIF-8 on the fibers result in a thickness of ~3 µm, with adequate thermal stability, and mechanical integrity when tested with methanol and acetonitrile ultrasonic treatments. The fibers have been evaluated in direct immersion mode using gas chromatography and flame ionization detection (GC-FID), for a group of target analytes including three polycyclic aromatic hydrocarbons (PAHs) and five personal care products (PCPs). The optimized conditions of the SPME-GC-FID methods include low amount of aqueous sample (5 mL), stirring for 45 min at 35 °C, and desorption at 280 °C for 5 min. The method presents limits of detection down to 0.6 µg L-1; intra-day, inter-day and inter-batch relative standard deviation values lower than 16%, 19%, and 23%, respectively; and a lifetime higher than 70 cycles.

3.
Talanta ; 211: 120723, 2020 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-32070617

RESUMO

Core-shell SiO2@CIM-80(Al) microspheres were synthesized, characterized, and used as novel sorbent in a dispersive miniaturized solid-phase extraction (D-µSPE) method for the determination of fourteen polycyclic aromatic hydrocarbons (PAHs) in wastewaters by ultra-high performance liquid chromatography coupled to a fluorescence detector (UHPLC-FD). A Doehlert experimental design permitted to optimize the main parameters affecting the microextraction procedure, intending the obtaining of a simple approach. Optimized extraction conditions include 13 mg of SiO2@CIM-80(Al) microparticles (~2 mg CIM-80(Al)), 2.5 min of extraction time, 0.125 mL of acetonitrile (ACN) as desorption solvent and 0.5 min of desorption time. The entire method showed adequate analytical performance with limits of detection down to 5 ng L-1, and inter-day precision lower than 14.1% for a concentration level of 0.5 µg L-1. The extraction capability of SiO2@CIM-80(Al) microspheres was compared to that obtained with commercially available silica microspheres and the neat MOF CIM-80(Al), demonstrating the advantages of the use of MOF core-shell sorbents in D-µSPE.

4.
Molecules ; 24(20)2019 Oct 10.
Artigo em Inglês | MEDLINE | ID: mdl-31658737

RESUMO

The mixed-ligand strategy was selected as an approach to tailor a metal-organic framework (MOF) with microextraction purposes. The strategy led to the synthesis of up to twelve UiO-66-based MOFs with different amounts of functionalized terephthalate ligands (H-bdc), including nitro (-NO2) and amino (-NH2) groups (NO2-bdc and NH2-bdc, respectively). Increases of 25% in ligands were used in each case, and different pore environments were thus obtained in the resulting crystals. Characterization of MOFs includes powder X-ray diffraction, infrared spectroscopy, and elemental analysis. The obtained MOFs with different degrees and natures of functionalization were tested as sorbents in a dispersive miniaturized solid-phase extraction (D-µSPE) method in combination with high-performance liquid chromatography (HPLC) and diode array detection (DAD), to evaluate the influence of mixed functionalization of the MOF on the analytical performance of the entire microextraction method. Eight organic pollutants of different natures were studied, using a concentration level of 5 µg· L-1 to mimic contaminated waters. Target pollutants included carbamazepine, 4-cumylphenol, benzophenone-3, 4-tert-octylphenol, 4-octylphenol, chrysene, indeno(1,2,3-cd)pyrene, and triclosan, as representatives of drugs, phenols, polycyclic aromatic hydrocarbons, and disinfectants. Structurally, they differ in size and some of them present polar groups able to form H-bond interactions, either as donors (-NH2) or acceptors (-NO2), permitting us to evaluate possible interactions between MOF pore functionalities and analytes' groups. As a result, extraction efficiencies can reach values of up to 60%, despite employing a microextraction approach, with four main trends of behavior being observed, depending on the analyte and the MOF.


Assuntos
Estruturas Metalorgânicas/química , Hidrocarbonetos Policíclicos Aromáticos/química , Microextração em Fase Sólida , Cromatografia Líquida de Alta Pressão , Ligantes
5.
Dalton Trans ; 48(27): 10260-10274, 2019 Jul 21.
Artigo em Inglês | MEDLINE | ID: mdl-31204755

RESUMO

We herein present the synthesis, spectroscopic analysis, description of the crystal structures and magnetic properties of four new complexes of the formula [{Cu(opba)(H2O)1.2}{Cu(dmphen)(SCN)}2]·dmf (1), [{Cu(opba)}2{Cu(dmphen)Cl}4]·1.5dmf·2.5dmso (2), [{Cu(opba)}2{Cu(dmphen)Br}4]·dmf·2.3dmso (3) and [{Cu(opba)}{Cu(dmphen)(dca)}2]n (4) [H4opba = N,N'-1,2-phenylenebis(oxamic acid), dmphen = 2,9-dimethyl-1,10-phenanthroline and dca = dicyanamide anion]. 1 is a neutral tricopper(ii) complex where an inner [Cu(opba)]2- fragment adopts a bis-bidentate coordination mode towards two outer [Cu(dmphen)(NCS)]+ units. 2 and 3 are bis-trinuclear species where two oxamato-bridged [Cu(opba){Cu(dmphen)X}2] [X = Cl- (2) and Br- (3)] tricopper(ii) entities are connected by two single X ions involving the central and one of the peripheral copper(ii) ions. 4 is a neutral chain made up of oxamato-bridged [Cu(opba){Cu(dmphen)(dca)}2] fragments linked through a single end-to-end dicyanamide ligand that connects the central copper(ii) ion with one of the peripheral copper(ii) ions. Magnetic susceptibility measurements on polycrystalline samples of 1-4 in the temperature range 1.9-300 K show the occurrence of strong antiferromagnetic interactions between the copper(ii) ions through the oxamate bridge [J = -328(2) (1), -288(2) (2), -431(2) (3) and -370(1) cm-1 (4), the Hamiltonian being defined as H = -J(S1·S2 + S1·S3)] and a weak ferromagnetic coupling across the equatorial-axial exchange pathway provided by the single halide bridge [j = +3.08(3) (2) and +2.34(1) cm-1 (3)]. These values are analyzed by simple orbital symmetry considerations and compared with those reported in the literature for polynuclear copper(ii) complexes with these bridging ligands.

6.
Molecules ; 24(4)2019 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-30769919

RESUMO

The pillared-layer Zn-triazolate metal-organic framework (CIM-81) was synthesized, characterized, and used for the first time as a sorbent in a dispersive micro-solid phase extraction method. The method involves the determination of a variety of personal care products in wastewaters, including four preservatives, four UV-filters, and one disinfectant, in combination with ultra-high performance liquid chromatography and UV detection. The CIM-81 MOF, constructed with an interesting mixed-ligand synthetic strategy, demonstrated a better extraction performance than other widely used MOFs in D-µSPE such as UiO-66, HKUST-1, and MIL-53(Al). The optimization of the method included a screening design followed by a Doehlert design. Optimum conditions required 10 mg of CIM-81 MOF in 10 mL of the aqueous sample at a pH of 5, 1 min of agitation by vortex and 3 min of centrifugation in the extraction step; and 1.2 mL of methanol and 4 min of vortex in the desorption step, followed by filtration, evaporation and reconstitution with 100 µL of the initial chromatographic mobile phase. The entire D-µSPE-UHPLC-UV method presented limits of detection down to 0.5 ng·mL-1; intra-day and inter-day precision values for the lowest concentration level (15 ng·mL-1)-as a relative standard deviation (in %)-lower than 8.7 and 13%, respectively; average relative recovery values of 115%; and enrichment factors ranging from ~3.6 to ~34. The reuse of the CIM-81 material was assessed not only in terms of maintaining the analytical performance but also in terms of its crystalline stability.


Assuntos
Estruturas Metalorgânicas/química , Extração em Fase Sólida , Triazóis/química , Águas Residuárias/química , Zinco/química , Reprodutibilidade dos Testes , Extração em Fase Sólida/métodos , Solventes/química , Análise Espectral , Poluentes Químicos da Água/química
7.
Molecules ; 23(11)2018 Nov 03.
Artigo em Inglês | MEDLINE | ID: mdl-30400309

RESUMO

Four metal-organic frameworks (MOFs), specifically UiO-66, UiO-66-NH2, UiO-66-NO2, and MIL-53(Al), were synthesized, characterized, and used as sorbents in a dispersive micro-solid phase extraction (D-µSPE) method for the determination of nine pollutants of different nature, including drugs, phenols, polycyclic aromatic hydrocarbons, and personal care products in environmental waters. The D-µSPE method, using these MOFs as sorbents and in combination with high-performance liquid chromatography (HPLC) and diode-array detection (DAD), was optimized. The optimization study pointed out to UiO-66-NO2 as the best MOF to use in the multi-component determination. Furthermore, the utilization of isoreticular MOFs based on UiO-66 with the same topology but different functional groups, and MIL-53(Al) to compare with, allowed us for the first time to evaluate the influence of such functionalization of the ligand with regards to the efficiency of the D-µSPE-HPLC-DAD method. Optimum conditions included: 20 mg of UiO-66-NO2 MOF in 20 mL of the aqueous sample, 3 min of agitation by vortex and 5 min of centrifugation, followed by the use of only 500 µL of acetonitrile as desorption solvent (once the MOF containing analytes was separated), 5 min of vortex and 5 min of centrifugation. The validation of the D-µSPE-HPLC-DAD method showed limits of detection down to 1.5 ng·L-1, average relative recoveries of 107% for a spiked level of 1.50 µg·L-1, and inter-day precision values with relative standard deviations lower than 14%, for the group of pollutants considered.


Assuntos
Microextração em Fase Sólida/métodos , Poluentes Químicos da Água/análise , Cromatografia Líquida de Alta Pressão/métodos , Hidrocarbonetos Policíclicos Aromáticos/química , Extração em Fase Sólida/métodos , Solventes/química
8.
Talanta ; 179: 775-783, 2018 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-29310307

RESUMO

Five metal-organic frameworks (MOFs), specifically HKUST-1, MOF-5(Zn), MIL-53(Al), UiO-64 and MOF-74(Zn) are synthesized, characterized, and utilized in a miniaturized solid-phase extraction method under dispersive mode (D-µSPE) for the determination of six pollutants of different nature, including one polycyclic aromatic hydrocarbon, two hormones, two drugs, and one disinfectant, from environmental waters (tap water and wastewater). A discussion of possible interactions justifying the partitioning of target analytes to the MOFs is included, considering not only the analytes' physicochemical characteristics but also those of MOFs: metal nature, structural environment of MOF pores, pore size and pore aperture widths, among others. MIL-53(Al) is selected for its versatility and high extraction efficiency for the target compounds. The D-µSPE method using MIL-53(Al) is optimized and used in combination with high-performance liquid chromatography (HPLC) with diode array detector (DAD) or liquid-chromatography with time-of-flight mass spectrometric detector (LC-TOF). Under optimum conditions, only 5mg of MIL-53(Al) are required for 10mL of water, with the aid of 5min of vortex and 5min of centrifugation. Elution is accomplished with 200µL of acetonitrile (3 times), and evaporation down to 100µL before LC injection. Detection limits down to 0.040µgL-1 for triclosan and 0.013µgL-1 for atrazine are obtained for the entire method using HPLC-DAD and LC-TOF, respectively. The method, operating at low spiked levels (2µgL-1 for HPLC-DAD and 0.7µgL-1 for LC-TOF), is also characterized for average relative recoveries of 109% and 105%; relative standard deviation values lower than 8.7% and 7.5%; and average extraction efficiencies of 41.2% and 49.1%; using HPLC-DAD and LC-TOF, respectively; while demonstrating adequate analytical performance with complex samples such as wastewaters.

9.
Dalton Trans ; 46(43): 15130-15137, 2017 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-29068025

RESUMO

A novel three-dimensional (3D) coordination polymer with the formula (C3N2H5)4[MnCr2(ox)6]·5H2O (2), where ox = oxalate and C3N2H5 = imidazolium cation, is reported. Single crystal X-ray diffraction reveals that this porous coordination polymer adopts a chiral three-dimensional quartz-like architecture, with the guest imidazolium cations and water molecules being hosted in its pores. This novel multifunctional material exhibits both a ferromagnetic ordering at TC = 3.0 K, related to the host MnCr2 network, and high proton conductivity [1.86 × 10-3 S cm-1 at 295 K and 88% relative humidity (RH)] due to the presence of the acidic imidazolium cations and free water molecules. The similarity of the structure of compound 2 to that of the previously reported analogous compound (NH4)4[MnCr2(ox)6]·4H2O, (1), also allows us to analyse, to a certain extent, the effect of the acidity of the proton donating guest molecules on proton conduction properties. 2 hosts, in one-dimensional (1D) channels, imidazolium cations, which are more acidic than the ammonium ones in 1 and, as a consequence, 2 shows higher proton conduction than 1, highlighting the effect of the pKa of the proton donating guest molecules on proton conductivity.

10.
Inorg Chem ; 56(4): 2108-2123, 2017 Feb 20.
Artigo em Inglês | MEDLINE | ID: mdl-28157308

RESUMO

In the series described in this work, the hydrothermal synthesis led to oxidation of the 5-methyl-pyrazinecarboxylate anion to the 2,5-pyrazinedicarboxylate dianion (2,5-pzdc) allowing the preparation of three-dimensional (3D) lanthanide(III) organic frameworks of formula {[Ln2(2,5-pzdc)3(H2O)4]·6H2O}n [Ln = Ce (1), Pr (2), Nd (3), and Eu (4)] and {[Er2(2,5-pzdc)3(H2O)4]·5H2O}n (5). Single-crystal X-ray diffraction on 1-5 reveals that they crystallize in the triclinic system, P1̅ space group with the series 1-4 being isostructural. The crystal structure of the five compounds are 3D with the lanthanide(III) ions linked through 2,5-pzdc2- dianions acting as two- and fourfold connectors, building a binodal 4,4-connected (4·648)(426282)-mog network. The photophysical properties of the Nd(III) (3) and Eu(III) (4) complexes exhibit sensitized photoluminescence in the near-infrared and visible regions, respectively. The photoluminescence intensity and lifetime of 4 were very sensitive due to the luminescence quenching of the 5D0 level by O-H oscillators of four water molecules in the first coordination sphere leading to a quantum efficiency of 11%. Variable-temperature magnetic susceptibility measurements for 1-5 reveal behaviors as expected for the ground terms of the magnetically isolated rare-earth ions [2F5/2, 2H4, 4I9/2, 7F0, and 4I15/2 for Ce(III), Pr(III), Nd(III), Eu(III), and Er(III), respectively] with MJ = 0 (2 and 4) and ±1/2 (1, 3, and 5). Q-band electron paramagnetic resonance measurements at low temperature corroborate these facts. Frequency-dependent alternating-current magnetic susceptibility signals under external direct-current fields in the range of 100-2500 G were observed for the Kramers ions of 1, 3, and 5, indicating slow magnetic relaxation (single-ion magnet) behavior. In these compounds, τ-1 decreases with decreasing temperature at any magnetic field, but no Arrhenius law can simulate such a dependence in all the temperature range. This dependence can be reproduced by the contributions of direct and Raman processes, the Raman exponent (n) reaching the expected value (n = 9) for a Kramers system.

11.
Anal Chim Acta ; 939: 26-41, 2016 Oct 05.
Artigo em Inglês | MEDLINE | ID: mdl-27639141

RESUMO

Solid-phase microextraction (SPME) is a powerful technique commonly used in sample preparation for extraction/preconcentration of analytes from a wide variety of samples. Among the trends in improving SPME applications, current investigations are focused on the development of novel coatings able to improve the extraction efficiency, sensitivity, and thermal and mechanical stability, within other properties, of current commercial SPME fibers. Metal-organic frameworks (MOFs) merit to be highlighted as promising sorbent materials in SPME schemes. MOFs are porous hybrid materials composed by metal ions and organic linkers, presenting the highest surface areas known, with ease synthesis and high tuneability, together with adequate chemical and thermal stability. For MOF based-SPME fibers, it results important to pretreat adequately the SPME supports to ensure the correct formation of the MOF onto the fiber or the attachment MOF-support. This, in turn, will increase the final stability of the fiber while generating uniform coatings. This review provides a critical overview of the current state of the use of MOFs as SPME coatings, not only highlighting the advantages of these materials versus commercial SPME coatings in terms of stability, selectivity, and sensitivity; but also insightfully describing the current methods to obtain reproducible MOF-based SPME coatings.

12.
J Chromatogr A ; 1436: 42-50, 2016 Mar 04.
Artigo em Inglês | MEDLINE | ID: mdl-26852621

RESUMO

A hybrid material composed by the metal-organic framework (MOF) HKUST-1 and Fe3O4 magnetic nanoparticles (MNPs) has been synthetized in a quite simple manner, characterized, and used in a magnetic-assisted dispersive micro-solid-phase extraction (M-d-µSPE) method in combination with ultra-high-performance liquid chromatography (UHPLC) and fluorescence detection (FD). The application was devoted to the determination of 8 heavy polycyclic aromatic hydrocarbons (PAHs) in different aqueous samples, specifically tap water, wastewaters, and fruit tea infusion samples. The overall M-d-µSPE-UHPLC-FD method was optimized and validated. The method is characterized by: its simplicity in both the preparation of the hybrid material (simple mixing) and the magnetic-assisted approach (∼10min extraction time), the use of low sorbent amounts (20mg of HKUST-1 and 5mg of Fe3O4 MNPs), and the low organic solvent consumption in the overall M-d-µSPE-UHPLC-FD method (1.5mL of acetonitrile in the M-d-µSPE method and 2.8mL of acetonitrile in the UHPLC-FD run). The resulting method has high sensitivity, with LODs down to 0.8ngL(-1); adequate intermediate precision, with relative standard deviation values (RSD) always lower than 6.3% (being the range 5.9-9.0% in tap water for a spiked level of 45ngL(-1), 6.1-14% in wastewaters for a spiked level of 45ngL(-1), and 7.2-17% in fruit tea infusion samples for a spiked level of 45ngL(-1)); and adequate relative recoveries, with average values of 82% in tap water, and 94% and 75% in wastewater and fruit tea infusion samples, respectively, if using the proper matrix-matched calibration.


Assuntos
Bebidas/análise , Frutas/química , Nanopartículas de Magnetita/química , Compostos Organometálicos/química , Hidrocarbonetos Policíclicos Aromáticos/análise , Extração em Fase Sólida/métodos , Poluentes Químicos da Água/análise , Cromatografia Líquida de Alta Pressão/métodos , Limite de Detecção , Solventes , Águas Residuárias/análise
14.
Chemistry ; 22(2): 539-45, 2016 Jan 11.
Artigo em Inglês | MEDLINE | ID: mdl-26603579

RESUMO

Single-ion magnets (SIMs) are the smallest possible magnetic devices and are a controllable, bottom-up approach to nanoscale magnetism with potential applications in quantum computing and high-density information storage. In this work, we take advantage of the promising, but yet insufficiently explored, solid-state chemistry of metal-organic frameworks (MOFs) to report the single-crystal to single-crystal inclusion of such molecular nanomagnets within the pores of a magnetic MOF. The resulting host-guest supramolecular aggregate is used as a playground in the first in-depth study on the interplay between the internal magnetic field created by the long-range magnetic ordering of the structured MOF and the slow magnetic relaxation of the SIM.

15.
Inorg Chem ; 54(22): 10834-40, 2015 Nov 16.
Artigo em Inglês | MEDLINE | ID: mdl-26492551

RESUMO

We report two novel three-dimensional porous coordination polymers (PCPs) of formulas Li4{Mn4[Cu2(Me3mpba)2]3}·68H2O (2) and K4{Mn4[Cu2(Me3mpba)2]3}·69H2O (3) obtained-via alkali cation exchange in a single-crystal to single-crystal process-from the earlier reported anionic manganese(II)-copper(II) PCP of formula Na4{Mn4[Cu2(Me3mpba)2]3}·60H2O (1) [Me3mpba(4-) = N,N'-2,4,6-trimethyl-1,3-phenylenebis(oxamate)]. This postsynthetic process succeeds where the direct synthesis in solution from the corresponding building blocks fails and affords significantly more robust PCPs with enhanced magnetic properties [long-range 3D magnetic ordering temperatures for the dehydrated phases (1'-3') of 2.0 (1'), 12.0 (2'), and 20.0 K (3')]. Changes in the adsorptive properties upon postsynthetic exchange suggest that the nature, electrostatic properties, mobility, and location of the cations within the framework are crucial for the enhanced structural stability. Overall, these results further confirm the potential of postsynthetic methods (including cation exchange) to obtain PCPs with novel or enhanced physical properties while maintaining unaltered their open-framework structures.

16.
Inorg Chem ; 54(18): 8890-2, 2015 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-26322529

RESUMO

A unique chiral three-dimensional magnet with an overall racemic double-interpenetrated (10,3)-a structure of the formula [(S)-(1-PhEt)Me3N]4[Mn4Cu6(Et2pma)12](DMSO)3]·3DMSO·5H2O (1; Et2pma = N-2,6-diethylphenyloxamate) has been synthesized by the self-assembly of a mononuclear copper(II) complex acting as a metalloligand toward Mn(II) ions in the presence of a chiral cationic auxiliary, constituting the first oxamato-based chiral coordination polymer exhibiting long-range magnetic ordering.

17.
Angew Chem Int Ed Engl ; 54(22): 6521-5, 2015 May 26.
Artigo em Inglês | MEDLINE | ID: mdl-25873186

RESUMO

A single crystal to single crystal transmetallation process takes place in the three-dimensional (3D) metal-organic framework (MOF) of formula Mg(II) 2 {Mg(II) 4 [Cu(II) 2 (Me3 mpba)2 ]3 }⋅45 H2 O (1; Me3 mpba(4-) =N,N'-2,4,6-trimethyl-1,3-phenylenebis(oxamate)). After complete replacement of the Mg(II) ions within the coordination network and those hosted in the channels by either Co(II) or Ni(II) ions, 1 is transmetallated to yield two novel MOFs of formulae Co2 (II) {Co(II) 4 [Cu(II) 2 (Me3 mpba)2 ]3 }⋅56 H2 O (2) and Ni2 (II) {Ni(II) 4 [Cu(II) 2 (Me3 mpba)2 ]3 }⋅ 54 H2 O (3). This unique postsynthetic metal substitution affords materials with higher structural stability leading to enhanced gas sorption and magnetic properties.

18.
Talanta ; 139: 13-20, 2015 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-25882402

RESUMO

Three metal-organic frameworks (MOFs), specifically HKUST-1, MOF-5, and MIL-53(Al), have been synthetized, characterized, studied and compared in a vortex-assisted dispersive micro-solid-phase extraction (VA-D-µ-SPE) procedure in combination with high-performance liquid chromatography (HPLC) with diode-array detection (DAD) for determining seven parabens in environmental waters (tap water, swimming pool water, and water coming from a spa pool), human urine (from two volunteers), and cosmetic creams (two commercial brands). Experimental parameters, such as nature and amount of MOF, sample volume, nature of elution solvent and its amount, vortex and centrifugation time, among others, were properly optimized. HKUST-1 was the most adequate MOF to work with. Detection limits for the overall method down to 0.1 µgL(-1) for butylparaben (BPB) and benzylparaben (BzPB) were obtained, with determination coefficients (R(2)) higher than 0.9966 for a range of 0.5-147 µgL(-1) (depending on the paraben), average relative recoveries (RR, in %) of 80.3% at the low spiked level (7 µgL(-1)), and relative standard deviation (RSD) values below 10% also at the low spiked level. The strength of the affinity between HKUST-1 and parabens was evaluated, and it ranged from 33.5% for isopropylparaben (iPPB) to 77.0% for isobutylparaben (iBPB). When analyzing complex environmental waters, RR values of 78%, inter-day precision values (as RSD) lower than 15%, and intra-day precision values lower than 7.8% were obtained, despite the observed matrix effect. When analyzing cosmetic creams, parabens were detected, with contents ranging from 0.14 ± 0.01 µgg(-1) for EPB in the healing cream analyzed to 1.12 ± 0.07 mgg(-1) for MPB in the mask cream analyzed, with precision values (RSD) lower than 12% and RR values from 63.7% for propylparaben (PPB) to 121% for iPPB. When analyzing human urine, no parabens were detected but the method could be performed with RSD values lower than 19%. These results show the adequateness of MOFs as sorbents in VA-D-µ-SPE procedures despite sample complexity.


Assuntos
Cosméticos/química , Metais/química , Compostos Organometálicos/química , Parabenos/análise , Parabenos/isolamento & purificação , Extração em Fase Sólida/métodos , Urina/química , Poluentes Químicos da Água/análise , Cromatografia Líquida de Alta Pressão/instrumentação , Cromatografia Líquida de Alta Pressão/métodos , Humanos , Urinálise
19.
Inorg Chem ; 53(12): 6299-308, 2014 Jun 16.
Artigo em Inglês | MEDLINE | ID: mdl-24901707

RESUMO

Six new heterometallic cobalt(II)-lanthanide(III) complexes of formulas [Ln(bta)(H2O)2]2[Co(H2O)6]·10H2O [Ln = Nd(III) (1) and Eu(III) (2)] and [Ln2Co(bta)2(H2O)8]n·6nH2O [Ln = Eu(III) (3), Sm(III) (4), Gd(III) (5), and Tb(III) (6)] (H4bta = 1,2,4,5-benzenetretracaboxylic acid) have been synthesized and characterized via single-crystal X-ray diffraction. 1 and 2 are isostructural compounds with a structure composed of anionic layers of [Ln(bta)(H2O)2]n(n-) sandwiching mononuclear [Co(H2O)6](2+) cations plus crystallization water molecules, which are interlinked by electrostatic forces and hydrogen bonds, leading to a supramolecular three-dimensional network. 3-6 are also isostructural compounds, and their structure consists of neutral layers of formula [Ln2Co(bta)2(H2O)8]n and crystallization water molecules, which are connected through hydrogen bonds to afford a supramolecular three-dimensional network. Heterometallic chains formed by the regular alternation of two nine-coordinate lanthanide(III) polyhedra [Ln(III)O9] and one compressed cobalt(II) octahedron [Co(II)O6] along the crystallographic c-axis are cross-linked by bta ligands within each layer of 3-6. Magnetic susceptibility measurements on polycrystalline samples for 3-6 have been carried out in the temperature range of 2.0-300 K. The magnetic behavior of these types of Ln(III)-Co(II) complexes, which have been modeled by using matrix dagonalization techniques, reveals the lack of magnetic coupling for 3 and 4, and the occurrence of weak antiferromagnetic interactions within the Gd(III)-Gd(III) (5) and Tb(III)-Tb(III) (6) dinuclear units through the exchange pathway provided by the double oxo(carboxylate) and double syn-syn carboxylate bridges.

20.
Inorg Chem ; 53(11): 5674-83, 2014 Jun 02.
Artigo em Inglês | MEDLINE | ID: mdl-24832918

RESUMO

A novel cobalt(II) complex of formula [Co2(cbut)(H2O)3]n (1) (H4cbut = 1,2,3,4-cyclobutanetetracarboxylic acid) has been synthesized under hydrothermal conditions and its crystal structure has been determined by means of synchrotron radiation and neutron powder diffraction. The crystal structure of 1 consists of layers of cobalt(II) ions extending in the bc-plane which are pillared along the crystallographic a-axis through the skeleton of the cbut(4-) ligand. Three crystallographically independent cobalt(II) ions [Co(1), Co(2), and Co(3)] occur in 1. They are all six-coordinate with four carboxylate-oxygens [Co(1)-Co(3)] and two cis-[Co(1)] or trans-water molecules [Co(2) and Co(3)] building distorted octahedral surroundings. Regular alternating double oxo(carboxylate) [between Co(1) and Co(1a)] and oxo(carboxylate) plus one aqua and a syn-syn carboxylate bridges [between Co(1) and Co(2)] occur along the crystallographic b-axis, the values of the cobalt-cobalt separation being 3.1259(8) and 3.1555(6) Å, respectively. These chains are connected to the Co(3) atoms through the OCO carboxylate along the [011] direction leading to the organic-inorganic bc-layers with Co(1)-OCO(anti-syn)-Co(3) and Co(2)-OCO(anti-anti)-Co(3) distances of 5.750(2) and 4.872(1) Å. The shortest interlayer cobalt-cobalt separation through the cbut(4-) skeleton along the crystallographic a-axis is 7.028(2) Å. Variable-temperature magnetic susceptibility measurements show the occurrence of antiferromagnetic ordering with a Néel temperature of 5.0 K, followed by a field-induced ferromagnetic transition under applied dc fields larger than 1500 Oe. The magnetic structure of 1 has been elucidated at low temperatures in zero field by neutron powder diffraction measurements and was found to be formed by ferromagnetic chains running along the b-axis which are antiferromagnetically coupled with the Co(3) ions through the c-axis giving rise to noncompensated magnetic moments within each bc-layer (ferrimagnetic plane). The occurrence of an antitranslation operation between these layers produces a weak interlayer antiferromagnetic coupling along the a-axis which is overcome by dc fields greater than 1500 Oe resulting in a phase transition toward a ferromagnetic state (metamagnetic behavior).

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