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1.
J Inorg Biochem ; : 111092, 2020 May 05.
Artigo em Inglês | MEDLINE | ID: mdl-32461023

RESUMO

Two Cu(II) coordination complexes, C1 and C2 of the formula [Cu(4)2(H2O)2], have been prepared by reaction between CuCl2·2H2O and 7-ethoxycarbonylmethyl-5-methyl-1,2,4[1,5-a]pyrimidine (L) in a 1:2 M:L molar ratio. The L molecule decomposes during the reaction process into 7-carboxy-5-methyl-[1,2,4]-triazolo[1,5-a]pyrimidine (4) through an intermediate, ethyl 2,2-dihydroxy-2-(5-methyl-[1,2,4]triazolo[1,5-a]pyrimidin-7-yl)acetate (5), which has been isolated and its crystal structure determined by X-ray diffraction. The X-ray analysis of the single crystals of [Cu(4)2(H2O)2] obtained from the slow evaporation of EtOH and MeOH, separately, revealed the formation of "solvent induced" polymorphs C1 and C2, respectively. The primary supramolecular synthon for C1 and C2 are six membered ring, and square shaped hydrogen bonded architecture, respectively. The self-assembly of such synthons resulted in a two dimensional hydrogen bonded sheet supported by OH⋯O interactions. In addition, the antioxidant properties of the ligands and its complexes were evaluated in vitro using 1,1-diphenyl-2-picrylhydrazyl acid, 2,2'-azino-bis (3-ethylbenzothiazoline-6 sulfonic acid radical scavenging methods and ferric reducing antioxidant power.

2.
Chemistry ; 2020 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-32378754

RESUMO

Non-covalent interactions are important for directing protein folding across multiple intermediates and can even provide access to multiple stable structures with different properties and functions. Herein, we describe an approach for mimicking this behavior in the self-assembly of metal-organic cages. Two ligands whose bend angles are controlled by non-covalent interactions and one ligand lacking the above-mentioned interactions were synthesized and used for self-assembly with Pd 2+ . As these weak interactions are easily broken, the bend angles have a controlled flexibility giving access to M 2 ( L1 ) 4 , M 6 ( L2 ) 12 , and M 12 ( L2 ) 24 cages. By controlling the self-assembly conditions this process can be directed in a stepwise fashion. Additionally, the multiple endohedral hydrogen bonding sites on the ligand were found to play a role in the binding and discrimination of neutral guests.

3.
Nanomaterials (Basel) ; 9(9)2019 Aug 25.
Artigo em Inglês | MEDLINE | ID: mdl-31450701

RESUMO

Electronic systems and telecommunication devices based on low-power microwaves, ranging from 2 to 40 GHz, have massively developed in the last decades. Their extensive use has contributed to the emergence of diverse electromagnetic interference (EMI) phenomena. Consequently, EMI shielding has become a ubiquitous necessity and, in certain countries, a legal requirement. Broadband absorption is considered the only convincing EMI shielding solution when the complete disappearance of the unwanted microwave is required. In this study, a new type of microwave absorber materials (MAMs) based on reduced graphene oxide (rGO) decorated with zero-valent Fe@γ-Fe2O3 and Fe/Co/Ni carbon-protected alloy nanoparticles (NPs) were synthesized using the Pechini sol-gel method. Synthetic parameters were varied to determine their influence on the deposited NPs size and spatial distribution. The deposited superparamagnetic nanoparticles were found to induce a ferromagnetic resonance (FMR) absorption process in all cases. Furthermore, a direct relationship between the nanocomposites' natural FMR frequency and their composition-dependent saturation magnetization (Ms) was established. Finally, the microwave absorption efficiency (0.4 MHz to 20 GHz) of these new materials was found to range from 60% to 100%, depending on the nature of the metallic particles grafted onto rGO.

4.
ACS Omega ; 4(2): 3954-3964, 2019 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-31459604

RESUMO

Efficient materials capable of capturing toxic metals from water are widely needed. Herein, a new pyridylpyrazole-ß-ketoenol receptor, X-ray diffraction analyzed, was covalently incorporated into the silica surface to produce solid and recyclable adsorbent particles. The new material, fully characterized, revealed extremely efficient removal of toxic metals from water, with a selectivity order of Pb(II) > Zn(II) > Cu(II) > Cd(II). The adsorption was exceptionally rapid at optimum pH and concentrations, showing Pb(II) removal of 93 mg g-1 within 5 min and maximum Pb(II) adsorption of 110 mg g-1 after only 20 min. Sorption isotherms agreed well with the Langmuir model suggesting a monolayer adsorption, whereas kinetics agreed with the pseudo-second-order model suggesting a chemisorption binding mechanism. Thermodynamics of adsorption were fitted with an endothermic and spontaneous process. The material, recyclable for at least five cycles, is therefore promising for the cleanup of water polluted by toxic metals, especially lead.

5.
Beilstein J Nanotechnol ; 10: 262-273, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30746320

RESUMO

A new hybrid adsorbent material for the efficient removal of heavy metals from natural real water solutions (Moroccan river water samples) was prepared by the immobilization of a new conjugated ß-ketoenol-pyridine-furan ligand onto a silica matrix. The thermodynamical properties including pH, adsorption isotherms, competitive adsorption, selectivity and regeneration were studied to investigate the effect of ketoenol-pyridine-furan-silica (SiNL) on the removal of Zn(II), Pb(II), Cd(II) and Cu(II) from aqueous solutions. An increase in adsorption as a function of pH and fast adsorption was reached within 25 min. The maximum sorption capacities for Zn(II), Pb(II), Cd(II) and Cu(II) were 96.17, 47.07, 48.30 and 32.15 mg·g-1, respectively. Furthermore, the material proved to be very stable - its adsorption capacity remained greater than 98% even after five cycles of adsorption/desorption. Compared to literature results, this material can be considered a high-performing remediation adsorbent for the extraction of Zn(II) from natural real water solution.

6.
J Inorg Biochem ; 191: 21-28, 2019 02.
Artigo em Inglês | MEDLINE | ID: mdl-30448715

RESUMO

In the present study, two pyrazole-acetamide derivatives namely N­(2­aminophenyl)­2­(5­methyl­1H­pyrazol­3­yl) acetamide (L1) and (E)­N­(2­(1­(2­hydroxy­6­methyl­4­oxo­4H­pyran­3­yl)ethylideneamino)phenyl)­2­(5­methyl­1H­pyrazol­3­yl) acetamide (L2) have been synthesized and characterized by infrared spectrophotometry (IR), nuclear magnetic resonance spectroscopy (NMR) and electrospray ionization-mass spectrometry (ESI-MS). Two coordination complexes of L1 and L2, namely [Co(L1)2(EtOH)2]·Cl2 (1) and [Cu(L2)]·H2O (2), respectively have been synthesized and characterized by elemental analysis and spectroscopic studies. The solid state structure of these two complexes was established by single crystal X-ray crystallography. In complex 1, the amide O and pyrazole N atoms of two molecules of L1 take part in coordination with octahedral Co(II) ions, the remaining two coordination sites being occupied by two EtOH molecules leading to a N2O4 coordination environment. On the other hand, the imine N atoms, pyrazole N and O atoms of the 2­hydroxy­6­methyl­4H­pyran­4­one function present in L2 are involved in coordination with Cu(II) ions, resulting in a distorted square planar geometry displaying a N2O4 chromophore, in complex 2. The crystal packing analysis of 1 and 2, revealed 1D and 2D supramolecular architectures respectively, via various hydrogen bonding interactions, which are discussed in the present account. Furthermore, the antioxidant activity of the ligands and their complexes were determined in vitro by 1,1­diphenyl­2­picrylhydrazyl (DPPH), 2,2'­azino­bis(3­ethylbenzothiazoline­6­sulphonic acid (ABTS) and ferric reducing antioxidant power(FRAP), showing that the ligands L1 and L2 and complexes 1 and 2 present significant antioxidant activity.


Assuntos
Antioxidantes/química , Cobalto/química , Complexos de Coordenação/química , Cobre/química , Acetamidas/química , Cristalografia por Raios X , Ligação de Hidrogênio , Ligantes , Estrutura Molecular , Pirazóis/química
7.
Inorg Chem ; 57(16): 9880-9891, 2018 Aug 20.
Artigo em Inglês | MEDLINE | ID: mdl-30080034

RESUMO

A series of bulky substituted bipyridine-related iron(II) complexes [Fe(H2Bpz2)2(L)] (pz = pyrazolyl) were prepared, where L = 5,5'-dimethyl-2,2'-bipyridine (bipy-CH3, 1), L = dimethyl-2,2'-bipyridyl-5,5'-dicarboxylate (MeObpydc, 2), L = diethyl-2,2'-bipyridyl-5,5'-dicarboxylate (EtObpydc, 3), or L = diisopropyl-2,2'-bipyridine-5,5'-dicarboxylate ( i-PrObpydc, 4). The crystal structures of five new iron(II) complexes were determined by X-ray diffraction: those of 1, 3, and 4 and two modifications of 3 (3B) and 4 (4B). Complexes 1 and 3B display incomplete spin crossover (SCO) behavior because of a freezing-in effect, whereas 3 and 4B undergo gradual and incomplete SCO behaviors. Complexes 2 and 4 show a completely gradual and steep SCO, respectively. Such different SCO behaviors can be attributed to an electronic substituent effect in the bipyridyl ligand conformation and a crystal packing effect. Importantly, the electronic substituent effect of the isopropyl acetate group and C-H···O supramolecular interactions in 4 contribute to a highly cooperative behavior, which leads to an abrupt thermally induced spin transition.

8.
Dalton Trans ; 47(20): 7013-7019, 2018 May 22.
Artigo em Inglês | MEDLINE | ID: mdl-29737355

RESUMO

Two polymorphic species of the [Fe(5-Br-salEen)2]ClO4 compound were obtained, each of them being selectively recovered after evaporation of the solvent at a controlled rate. While polymorph 1a is formed during slow evaporation, fast evaporation favors polymorph 1b. The importance of the evaporation rate was recognized after detailed studies of the reaction temperature, solvent evaporation rate and crystallization temperature effects. The complex in the new polymorphic form 1a showed an abrupt spin crossover at 172 K with a small 1 K hysteresis window and over a narrow 10 K range. 57Fe Mössbauer spectroscopy and differential scanning calorimetry, complemented by X-ray studies for both the high-spin and low-spin forms, were used to further characterize the new polymorphic phase 1a. Both polymorphs are based on the same Fe(iii) complex cation hydrogen bonded to the perchlorate anion. These units are loosely bound in the crystals via weak interactions. In the new polymorph 1a, the hydrogen bonds are stronger, while the weak hydrogen and halogen bonds, as well as π-π stacking, create a cooperative network, not present in 1b, responsible for the spin transition profile.

9.
J Hazard Mater ; 353: 312-319, 2018 07 05.
Artigo em Inglês | MEDLINE | ID: mdl-29679891

RESUMO

The covalent triazine framework, CTF-1, served as host material for the in situ synthesis of Fe2O3 nanoparticles. The composite material consisted of 20 ±â€¯2 m% iron, mainly in γ-Fe2O3 phase. The resulting γ-Fe2O3@CTF-1 was examined for the adsorption of AsIII, AsV and HgII from synthetic solutions and real surface-, ground- and wastewater. The material shows excellent removal efficiencies, independent from the presence of Ca2+, Mg2+ or natural organic matter and only limited dependency on the presence of phosphate ions. Its adsorption capacity towards arsenite (198.0 mg g-1), arsenate (102.3 mg g-1) and divalent mercury (165.8 mg g-1) belongs amongst the best-known adsorbents, including many other iron-based materials. Regeneration of the adsorbent can be achieved for use over multiple cycles without a decrease in performance by elution at 70 °C with 0.1 M NaOH, followed by a stirring step in a 5 m% H2O2 solution for As or 0.1 M thiourea and 0.001 M HCl for Hg. In highly contaminated water (100 µg L-1), the adsorbent polishes the water quality to well below the current WHO limits.

10.
Dalton Trans ; 45(36): 14008-18, 2016 Sep 28.
Artigo em Inglês | MEDLINE | ID: mdl-27513712

RESUMO

Electromagnetic stimuli of spin crossover compounds restricted to UV-vis light irradiation for many years could be recently extended to X-ray excitation. This review covers a large variety of light-induced effects, as well as recent analogues stimulated by X-ray irradiation which have not yet been reviewed. The focus is also on multistable multinuclear spin crossover compounds which are the subject of lively discussions within the spin crossover community. Their spin transition often occurs incompletely and with different switching mechanisms. In this review, we recall a predicted sequential switching induced thermally as well as a concerted stimulation mechanism by light irradiation for these interesting multifunctional materials.

11.
Inorg Chem ; 55(9): 4278-95, 2016 05 02.
Artigo em Inglês | MEDLINE | ID: mdl-27104913

RESUMO

A new family of one-dimensional Fe(II) 1,2,4-triazole spin transition coordination polymers for which a modification of anion and crystallization solvent can tune the switching temperature over a wide range, including the room temperature region, is reported. This series of materials was prepared as powders after reaction of ethyl-4H-1,2,4-triazol-4-yl-acetate (αEtGlytrz) with an iron salt from a MeOH/H2O medium affording: [Fe(αEtGlytrz)3](ClO4)2 (1); [Fe(αEtGlytrz)3](ClO4)2·CH3OH (2); [Fe(αEtGlytrz)3](NO3)2·H2O (3); [Fe(αEtGlytrz)3](NO3)2 (4); [Fe(αEtGlytrz)3](BF4)2·0.5H2O (5); [Fe(αEtGlytrz)3](BF4)2 (6); and [Fe(αEtGlytrz)3](CF3SO3)2·2H2O (7). Their spin transition properties were investigated by (57)Fe Mossbauer spectroscopy, superconducting quantum interference device (SQUID) magnetometry, and differential scanning calorimetry (DSC). The temperature dependence of the high-spin molar fraction derived from (57)Fe Mössbauer spectroscopy in 1 reveals an abrupt single step transition between low-spin and high-spin states with a hysteresis loop of width 5 K (Tc(↑) = 296 K and Tc(↓) = 291 K). The properties drastically change with modification of anion and/or lattice solvent. The transition temperatures, deduced by SQUID magnetometry, shift to Tc(↑) = 273 K and Tc(↓) = 263 K for (2), Tc(↑) = 353 K and Tc(↓) = 333 K for (3), Tc(↑) = 338 K and Tc(↓) = 278 K for (4), T(↑) = 320 K and T(↓) = 305 K for (5), Tc(↑) = 106 K and Tc(↓) = 92 K for (6), and T(↑) = 325 K and T(↓) = 322 K for (7). Annealing experiments of 3 lead to a change of the morphology, texture, and magnetic properties of the sample. A dehydration/rehydration process associated with a spin state change was analyzed by a mean-field macroscopic master equation using a two-level Hamiltonian Ising-like model for 3. A new structural-property relationship was also identified for this series of materials [Fe(αEtGlytrz)3](anion)2·nSolvent based on Mössbauer and DSC measurements. The entropy gap associated with the spin transition and the volume of the inserted counteranion shows a linear trend, with decrease in entropy with increasing the size of the counteranion. The first materials of this substance class to display a complete spin transition in both spin states are also presented.

12.
Sensors (Basel) ; 16(2): 187, 2016 Feb 02.
Artigo em Inglês | MEDLINE | ID: mdl-26848663

RESUMO

The possibility of a new design concept for dual spin crossover based sensors for concomitant detection of both temperature and pressure is presented. It is conjectured from numerical results obtained by mean field approximation applied to a Ising-like model that using two different spin crossover compounds containing switching molecules with weak elastic interactions it is possible to simultaneously measure P and T. When the interaction parameters are optimized, the spin transition is gradual and for each spin crossover compounds, both temperature and pressure values being identified from their optical densities. This concept offers great perspectives for smart sensing devices.

13.
Nanoscale ; 7(48): 20474-88, 2015 Dec 28.
Artigo em Inglês | MEDLINE | ID: mdl-26583487

RESUMO

Fe-filled carbon nanotubes (Fe@CNTs) recently emerged as an effective class of hybrid nanoparticles for biotechnological applications, such as magnetic cell sorting and magnetic fluid hyperthermia. Aiming at studying the effects of both the Fe loading and the magnetocrystalline characteristics in these applications, we describe herein the preparation of Fe@CNTs containing different Fe phases that, upon functionalization with the antibody Cetuximab (Ctxb), allow the targeting of cancer cells. Our experimental findings reveal that an optimal Ctxb/Fe weight ratio of 1.2 is needed for efficient magnetic cell shepherding, whereas enhanced MFH-induced mortality (70 vs. 15%) can be reached with hybrids enriched in the coercive Fe(3)C phase. These results suggest that a synergistic effect between the Ab loading and the Fe distribution in each nanotube exists, for which the maximum shepherding and hyperthermia effects are observed when higher densities of Fe@CNTs featuring the more coercive phase are interfaced with the cells.


Assuntos
Hipertermia Induzida , Ferro/química , Terapia de Campo Magnético , Campos Magnéticos , Nanotubos de Carbono/química , Ferro/uso terapêutico , Nanotubos de Carbono/ultraestrutura
14.
Chem Commun (Camb) ; 51(99): 17630, 2015 Dec 25.
Artigo em Inglês | MEDLINE | ID: mdl-26593385

RESUMO

Correction for 'Electronic vs. structural ordering in a manganese(III) spin crossover complex' by Anthony J. Fitzpatrick et al., Chem. Commun., 2015, DOI: 10.1039/c5cc05129k.

15.
Chemistry ; 21(46): 16679-87, 2015 Nov 09.
Artigo em Inglês | MEDLINE | ID: mdl-26423780

RESUMO

The reaction of the N-thiophosphorylated thiourea (HOCH2 )(Me)2 CNHC(S)NHP(S)(OiPr)2 (HL), deprotonated by the thiophosphorylamide group, with NiCl2 leads to green needles of the pseudotetrahedral complex [Ni(L-1,5-S,S')2 ]⋅0.5 (n-C6 H14 ) or pale green blocks of the trans square-planar complex trans-[Ni(L-1,5-S,S')2 ]. The former complex is stabilized by homopolar dihydrogen C-H⋅⋅⋅H-C interactions formed by n-hexane solvent molecules with the [Ni(L-1,5-S,S')2 ] unit. Furthermore, the dispersion-dominated C-H⋅⋅⋅ H-C interactions are, together with other noncovalent interactions (C-H⋅⋅⋅N, C-H⋅⋅⋅Ni, C-H⋅⋅⋅S), responsible for pseudotetrahedral coordination around the Ni(II) center in [Ni(L-1,5-S,S')2 ]⋅0.5 (n-C6 H14 ).

16.
Chem Commun (Camb) ; 51(99): 17540-3, 2015 Dec 25.
Artigo em Inglês | MEDLINE | ID: mdl-26501138

RESUMO

A symmetry breaking spin transition in a Mn(III) complex is reported with three structural phases, a high symmetry high temperature S = 2 phase, an intermediate S = 1/S = 2 ordered phase and an aperiodic low temperature phase with S = 1 cations. The aperiodicity is interpreted as resulting from long-range ordering of the NTf2(-) anions.

17.
Chemistry ; 21(36): 12769-77, 2015 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-26179742

RESUMO

The development of new electrocatalysts for the oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) at physiological pH is critical for several fields, including fuel cells and biological applications. Herein, the assembly of an electrode based on carboxyl-functionalised hydrophilic multiwalled carbon nanotubes (MWCNTs) filled with Fe phases and their excellent performance as electrocatalysts for ORR and HER at physiological pH are reported. The encapsulated Fe dramatically enhances the catalytic activity, and the graphitic shells play a double role of efficiently mediating the electron transfer to O2 and H2 O reactants and providing a cocoon that prevents uncontrolled Fe oxidation or leaching.

18.
Dalton Trans ; 44(29): 13186-95, 2015 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-26110738

RESUMO

3',6'-Bis(diethylamino)-2-(pyridin-2-ylmethyl)spiro[isoindoline-1,9'-xanthen]-3-one () was synthesized for the selective fluorescence and colorimetric recognition of Hg(2+) at pH 6.0. In addition, was useful for imaging Hg(2+) in fish kidney and liver tissues using a fluorescence microscope. Spirolactam ring opening of for Hg(2+) recognition is strongly influenced by the nature of the mercury salt and found to be NO3(-)-induced. Other mercury salts such as HgCl2, Hg(CH3COO)2 and Hg(ClO4)2 failed to induce fluorescence and colorimetric response of under the same experimental conditions. For instance, the former salt does not exhibit spirolactam ring opening but forms a new ionic compound (H3L)2[Hg6Cl18]·2H2O (), whose structure has been elucidated by single crystal X-ray diffraction. This might be explained by (1) the higher covalent nature of Hg(2+) and, hence, the lower acidity of the metal center and its inability to induce the ring opening reaction, and (2) the bulky anion, in the case of Hg(ClO4)2, which is also ionic, faces steric hindrance to accommodate within the N(Et)2 group upon spirolactam ring opening.


Assuntos
Corantes Fluorescentes/química , Rim/química , Fígado/química , Mercúrio/análise , Compostos de Espiro/química , Xantonas/química , Animais , Cristalografia por Raios X , Peixes , Microscopia de Fluorescência , Modelos Moleculares , Imagem Óptica , Rodaminas/química , Espectrometria de Fluorescência
20.
Chemistry ; 21(15): 5843-55, 2015 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-25736846

RESUMO

A thermochromic 1D spin crossover coordination (SCO) polymer [Fe(ßAlatrz)3](BF4)2⋅2 H2O (1⋅2 H2O), whose precursor ßAlatrz, (1,2,4-triazol-4-yl-propionate) has been tailored from a ß-amino acid ester is investigated in detail by a set of superconducting quantum interference device (SQUID), (57)Fe Mössbauer, differential scanning calorimetry, infrared, and Raman measurements. An hysteretic abrupt two-step spin crossover (T1/2(↓) = 230 K and T1/2(↑) = 235 K, and T1/2(↓) = 172 K and T1/2(↑) = 188 K, respectively) is registered for the first time for a 1,2,4-triazole-based Fe(II) 1D coordination polymer. The two-step SCO configuration is observed in a 1:2 ratio of low-spin/high-spin in the intermediate phase for a 1D chain. The origin of the stepwise transition was attributed to a distribution of chains of different lengths in 1⋅2 H2O after First Order Reversal Curves (FORC) analyses. A detailed DFT analysis allowed us to propose the normal mode assignment of the Raman peaks in the low-spin and high-spin states of 1⋅2 H2O. Vibrational spectra of 1⋅2 H2O reveal that the BF4(-) anions and water molecules play no significant role on the vibrational properties of the [Fe(ßAlatrz)3](2+) polymeric chains, although non-coordinated water molecules have a dramatic influence on the emergence of a step in the spin transition curve. The dehydrated material [Fe(ßAlatrz)3](BF4)2 (1) reveals indeed a significantly different magnetic behavior with a one-step SCO which was also investigated.

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