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1.
Molecules ; 25(13)2020 Jul 03.
Artigo em Inglês | MEDLINE | ID: mdl-32635351

RESUMO

New metal-organic frameworks (MOF) with lanthanum(III), cerium(III), neodymium(III), europium(III), gadolinium(III), dysprosium(III), and holmium(III)] and the ligand precursor 1,3,5-tris(4-carboxyphenyl)-2,4,6-trimethylbenzene (H3L) were synthesized under solvothermal conditions. Single crystal x-ray analysis confirmed the formation of three-dimensional frameworks of [LnL(H2O)2]n·xDMF·yH2O for Ln = La, Ce, and Nd. From the nitrogen sorption experiments, the compounds showed permanent porosity with Brunauer-Emmett-Teller (BET) surface areas of about 400 m2/g, and thermal stability up to 500 °C. Further investigations showed that these Ln-MOFs exhibit catalytic activity, paving the way for potential applications within the field of catalysis.

2.
Dalton Trans ; 2020 Apr 03.
Artigo em Inglês | MEDLINE | ID: mdl-32242883

RESUMO

Two new 2D spin-crossover (SCO) analogues of Hofmann clathrates of composition [Fe(phth)2MII(CN)4] (where phth = phthalazine; MII = Pd, Pt) have been synthesized and their structures and switchable behaviour have been characterized. Single-crystal X-ray analysis reveals that the Pt and Pd derivatives contain FeII centres equatorially surrounded by four equivalent µ4-[MII(CN)4]2- groups. Two crystallographically equivalent phthalazine (phth) ligands occupy the axial positions of each FeII site, completing its octahedral coordination environment. The stabilization of these structures is realized via supramolecular C-HM interactions and π-π stacking. Temperature-dependent magnetic susceptibility measurements showed that Pt (T1/2↓ = 211 K and T1/2↑ = 218 K) and Pd (T1/2↓ = 202 K and T1/2↑ = 207 K) derivatives display cooperative spin crossover with narrow thermal hysteresis loops. In addition, spin crossover in these complexes was characterized by optical measurements, differential scanning calorimetry, and IR and Raman spectroscopy. This research shows that the use of phthalazine leads to the production of new SCO systems with attractive transition characteristics and opens up new perspectives for the design of switchable complexes based on fused bicyclic azine ligands.

3.
ACS Appl Mater Interfaces ; 12(20): 23432-23442, 2020 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-32340440

RESUMO

The synthesis of novel dielectric elastomers that show a muscle-like actuation when exposed to a low electric field represents a major challenge in materials science. Silicone elastomers modified with polar side groups are among the most attractive dielectrics for such a purpose because of their high polarizability over a wide temperature and frequency range. Nitroaniline (NA) has a strong dipole moment, and therefore, its incorporation into silicone networks should allow the formation of elastomers with increased dielectric permittivity. However, incorporation of a large amount of NA into silicone needed to increase the dielectric permittivity is still challenging. In this work, we present the synthesis of polysiloxane elastomers modified with a large fraction of the nitroaniline (NA) polar group, following two different synthetic strategies. Both approaches allowed the formation of homogenous elastomers at the molecular level. These yellowish materials have a dielectric permittivity three times higher as compared to the reported NA-modified silicones. Additionally, they have excellent mechanical properties with low viscoelastic losses and a strain at break reaching 300%. Furthermore, the mechanical properties of these elastomers can be easily tuned by the content of cross-linkers used. The developed elastomers are highly stable in electromechanical tests and show an actuation strain of 8% at unprecedentedly low electric fields of 7.5 V/µm. The combination of properties such as high dielectric permittivity, large strain at break, low viscoelastic losses, fast and reversible actuation, and actuation at low electric fields is crucial for the new generation of dielectric elastomer materials that will find their way in applications ranging from artificial muscles, soft robots, sensors, and haptic displays to electronic skin.

4.
Inorg Chem ; 2020 Apr 17.
Artigo em Inglês | MEDLINE | ID: mdl-32301607

RESUMO

Hofmann-like cyanometalates constitute a large class of spin-crossover iron(II) complexes with variable switching properties. However, it is not yet clearly understood how the temperature and cooperativity of a spin transition are influenced by their structure. In this paper, we report the synthesis and crystal structures of the metal-organic coordination polymers {FeII(Mepz)[AuI(CN)2]2} ([Au]) and {FeII(Mepz)2[AgI(CN)2]2} ([Ag]), where Mepz = 2-methylpyrazine, along with characterization of their spin-state behavior by variable-temperature SQUID magnetometry and Mössbauer spectroscopy. The compounds are built of cyanoheterometallic layers, which are pillared by the bridging Mepz ligands in [Au] but separated in [Ag]. The complex [Au] exhibits an incomplete stepped spin transition as a function of the temperature with TSCO1 = 170 K and TSCO2 = 308 K for the two subsequent steps. In contrast, the complex [Ag] attains the high-spin state over the whole temperature range. In the crystal structure of [Ag], weak interlayer contacts (Ag-π, Me-π, and Ag-N) are found that may be responsible for an unusual axial elongation of the FeN6 polyhedra. We propose that this structural distortion contributes to the trapping of iron in its high-spin state.

5.
Inorg Chem ; 58(24): 16642-16659, 2019 Dec 16.
Artigo em Inglês | MEDLINE | ID: mdl-31750654

RESUMO

Four different crystal structures for quinolinehydroxamic acid (QuinHA) and picolinehydroxamic acid (PicHA) MCs with Cu(II) and Ni(II), and solution studies on the formation of Cu(II), Ni(II), and Zn(II) MC complexes with QuinHA, PicHA, and pyrazylohydroxamic acid (PyzHA) are described. In polynuclear complex 1, [Cu5(QuinHA-2H)4(NO3)(DMSO)4](NO3), the metallamacrocyclic cavity is formed by four Cu(II) ions and four doubly deprotonated hydroximate ligands, and the center of the cavity is occupied by the fifth Cu(II) ion coordinated by four hydroximate oxygen atoms. The complex 2, [Cu10(PicHA-2H)8(H2O)4(ClO4)3](ClO4)·4H2O, exhibits a dimeric structure based on two pentanuclear collapsed 12-MC-4 Cu4(PicHA-2H)4 fragments united by two chiral capping Cu(II) ions exo-coordinated to the peripheral vacant (O,O') chelating units of each tetranuclear collapsed MC moiety. 3, [CaNi5(QuinHA-2H)5(H2O)2(Py)10](NO3)2, and 4, [CaNi5(PicHA-2H)5(DMF)2(Py)8](NO3)2, are planar 15-membered rings consisting of a PicHA or QuinHA ligand, respectively. To understand fully the correlation between species isolated in the solid state and those presented in solution, the solution equilibria were investigated, showing the dependence of the MCs topologies and stability constants (log ß) on the ligand structure and metal ion.

6.
Acta Crystallogr E Crystallogr Commun ; 75(Pt 10): 1536-1539, 2019 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-31636989

RESUMO

In the title polymeric complex, {[FePt(CN)4(H2O)2]·2C3H6O} n , the FeII cation has an octa-hedral [FeN4O2] geometry being coordinated by two water mol-ecules and four cyanide anions. The Pt cation is located on an inversion centre and has a square-planar coordination environment formed by four cyanide groups. The tetra-cyano-platinate anions bridge the FeII cations to form infinite two-dimensional layers that propagate in the bc plane. Two guest mol-ecules of acetone per FeII are located between the layers. These guest acetone mol-ecules inter-act with the coordinated water mol-ecules by O-H⋯O hydrogen bonds.

7.
Acta Crystallogr E Crystallogr Commun ; 75(Pt 8): 1149-1152, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31417782

RESUMO

In the title polymeric complex, {[Fe(CN)2(C10H8N2)2(H2O)2][Au(CN)2]} n , the FeII ion, which is located on a twofold rotation axis, has a slightly distorted FeN4O2 octa-hedral geometry. It is coordinated by two phenyl-pyrazine mol-ecules, two water mol-ecules and two di-cyano-aurate anions, the Au atom also being located on a second twofold rotation axis. In the crystal, the coordinated di-cyano-aurate anions bridge the FeII ions to form polymeric chains propagating along the b-axis direction. In the crystal, the chains are linked by Owater-H⋯Ndi-cyano-aurate anions hydrogen bonds and aurophillic inter-actions [Au⋯Au = 3.5661 (3) Å], forming layers parallel to the bc plane. The layers are linked by offset π-π stacking inter-actions [inter-centroid distance = 3.643 (3) Å], forming a supra-molecular metal-organic framework.

8.
Inorg Chem ; 58(16): 11133-11145, 2019 Aug 19.
Artigo em Inglês | MEDLINE | ID: mdl-31373487

RESUMO

Nickel(II) complexes with 15-membered (1-5) and 14-membered (6) octaazamacrocyclic ligands derived from 1,2- and 1,3-diketones and S-methylisothiocarbohydrazide were prepared by template synthesis. The compounds were characterized by elemental analysis, electrospray ionization mass spectrometry, IR, UV-vis, 1H NMR spectroscopies, and X-ray diffraction. The complexes contain a low-spin nickel(II) ion in a square-planar coordination environment. The electrochemical behavior of 1-6 was investigated in detail, and the electronic structure of 1e-oxidized and 1e-reduced species was studied by electron paramagnetic resonance, UV-vis-near-IR spectroelectrochemistry, and density functional theory calculations indicating redox noninnocent behavior of the ligands. Compounds 1-6 were tested in the microwave-assisted solvent-free oxidation of cyclohexane by tert-butyl hydroperoxide to produce the industrially significant mixture of cyclohexanol and cyclohexanone (i.e., A/K oil). The results showed that the catalytic activity was affected by several factors, namely, reaction time and temperature or amount and type of catalyst. The best values for A/K oil yield (23%, turnover number of 1.1 × 102) were obtained with compound 6 after 2 h of microwave irradiation at 100 °C.

9.
Molecules ; 24(13)2019 Jul 04.
Artigo em Inglês | MEDLINE | ID: mdl-31277454

RESUMO

BACKGROUND: Due to the emergence of multidrug resistant microorganisms, new classes of antibiotics are needed. In this paper, we present the cytotoxic effects of five tricyclic flavonoids, one of which was previously identified as a potent antimicrobial agent. METHODS: All five derivatives were tested against human HOS and MCF7 cancer cell lines using a wound scratch assay. The cytotoxic properties of previously reported flavonoid 4a were also evaluated using the standard MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt) and live/dead assays, using NHDF, HOS and MCF7 cell lines. RESULTS: All five derivatives were found to inhibit to some degree the proliferation of cancer cells. 4a was also found to be less toxic towards regular versus cancerous human cells. Moreover, the minimum bactericidal concentration of 4a against Staphylococcus aureus was found to be non-toxic for any of the tested human cell lines. CONCLUSIONS: Derivative 4a has the potential of being used as a therapeutic agent against certain microorganisms. Further structure optimization is required for use against tumors.


Assuntos
Flavonoides/toxicidade , Morte Celular/efeitos dos fármacos , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Cristalografia por Raios X , Flavonoides/síntese química , Flavonoides/química , Humanos
10.
Dalton Trans ; 48(41): 15455-15464, 2019 Oct 22.
Artigo em Inglês | MEDLINE | ID: mdl-31204750

RESUMO

Five new cyanido-bridged heterometallic coordination polymers have been obtained by reacting PPh4[RuIII(salpn)(CN)2]·H2O (1) and AsPh4[RuIII(valen)(CN)2]·8.5H2O (2) (H2salpn and H2valen being Schiff-base proligands resulting from the condensation reaction of salicylaldehyde with 1,3-propanediamine and, respectively, o-vanillin with 1,2-ethanediamine) with divalent transition metal perchlorate salts: ∞1[{RuIII(salpn)(CN)2}3{MII(DMF)3}2](ClO4)·4DMF (MII = Mn, 3; Co, 4) and ∞2[{RuIII(valen)(CN)2}4{MII(DMF)3}2{MII(DMF)4}](ClO4)2·4DMF (MII = Mn, 5; Co, 6; Ni, 7), respectively. The dicyanido species, trans-[Ru(salpn)(CN)2]- and trans-[Ru(valen)(CN)2]-, act as metalloligands with the 3d metal ions. Compounds 3 and 4 are isostructural one-dimensional (1D) coordination polymers with a ladder topology. Each MII ion is hexacoordinated by three cyanido groups arising from three {Ru(salpn)(CN)2} units and by the oxygen atoms from three DMF molecules, which are coordinated at meridional positions. Compounds 5-7 are also isostructural, their structures consisting of 2D networks with a herringbone topology. The magnetic susceptibility measurements of these 1D and 2D systems reveal the presence of dominating RuIII-MII antiferromagnetic (AF) interactions in compounds 3, 4, 5 and 6, while ferromagnetic RuIII-NiII interactions are observed in 7. All these compounds stay in their paramagnetic state down to 1.8 K except compound 4 which possesses a 3D ordered AF ground state.

11.
Dalton Trans ; 48(22): 7532-7536, 2019 Jun 14.
Artigo em Inglês | MEDLINE | ID: mdl-31066421

RESUMO

Two new examples of cyanido-bridged {FeIIILnIII}2 molecular squares, with pyim and PPh3O as capping ligands at the LnIII sites, exhibit weak antiferromagnetic interactions [Ln = Eu (1), Sm (2), pyim = 2-(1H-imidazol-2-yl)pyridine, PPh3PO = triphenylphosphine oxide].

12.
Arch Pharm (Weinheim) ; 352(5): e1800227, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30947375

RESUMO

Unprecedented triazinyl-isoxazoles were afforded via an effective cycloaddition reaction between nitrile oxides and the scarcely described 2-ethynyl-4,6-dimethoxy-1,3,5-triazine as dipolarophile. The biological evaluation of the newly synthesized compounds showed that the inhibition of human farnesyltransferase by zinc complexation could be improved with triazine-isoxazole moieties. The replacement of the isoxazole unit by a pyrrolidin-2-one was detrimental to the inhibitory activity while the pyrrolidin-2-thione derivatives conserved the biological potential. The potential of selected compounds to disrupt protein farnesylation in Chinese hamster ovary (CHO) cells transfected with pEGFP-CAAX was also evaluated.


Assuntos
Inibidores Enzimáticos/farmacologia , Farnesiltranstransferase/antagonistas & inibidores , Isoxazóis/farmacologia , Pirrolidinonas/farmacologia , Triazinas/farmacologia , Animais , Células CHO , Cricetulus , Relação Dose-Resposta a Droga , Inibidores Enzimáticos/síntese química , Inibidores Enzimáticos/química , Farnesiltranstransferase/metabolismo , Humanos , Isoxazóis/química , Estrutura Molecular , Pirrolidinonas/química , Relação Estrutura-Atividade , Triazinas/química
13.
Chem Commun (Camb) ; 55(23): 3359-3362, 2019 Mar 14.
Artigo em Inglês | MEDLINE | ID: mdl-30816373

RESUMO

A new iron(ii)-based spin-crossover compound with thermal hysteresis operating under ambient conditions is reported. This complex exhibits a high reproducibility of the spin transition in many successive thermal cycles, stability of both spin states at room temperature and an attractive operational temperature range.

14.
Int J Mol Sci ; 20(3)2019 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-30736413

RESUMO

The development of UV⁻vis spectrophotometric methods based on metalloporphyrins for fast, highly sensitive and selective anion detection, which avoids several of the practical challenges associated with other detection methods, is of tremendous importance in analytical chemistry. In this study, we focused on achieving a selective optical sensor for triiodide ion detection in traces based on a novel hybrid material comprised of Pt(II) 5,10,15,20-tetra(4-methoxy-phenyl)-porphyrin (PtTMeOPP) and gold nanoparticles (AuNPs). This sensor has high relevance in medical physiological tests. The structure of PtTMeOPP was investigated by single crystal X-ray diffraction in order to understand the metal surroundings and the molecule conformation and to assess if it qualifies as a potential sensitive material. It was proven that the Pt-porphyrin generated 1D H-bond supramolecular chains due to the weak C-H···O intermolecular hydrogen bonding. The presence of ordered voids in the crystal encouraged us to use PtTMeOPP as the sensing material for triiodide ion and to enhance its potential in a novel AuNPs/PtTMeOPP hybrid by the synergistic effects provided by the plasmonic gold nanoparticles. The spectrophotometric sensor is characterized by a detection limit of 1.5 × 10-9 M triiodide ion concentration and a remarkable confidence coefficient of 99.98%.


Assuntos
Ânions/análise , Ouro , Iodetos/análise , Nanopartículas Metálicas , Metaloporfirinas/química , Modelos Moleculares , Compostos Organoplatínicos/química , Ouro/química , Nanopartículas Metálicas/química , Nanopartículas Metálicas/ultraestrutura , Microscopia de Força Atômica , Conformação Molecular , Termogravimetria
15.
Dalton Trans ; 48(18): 5909-5922, 2019 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-30638234

RESUMO

Three dimanganese(iii) complexes have been synthesised and fully characterised by standard spectroscopic methods and spectroelectrochemistry. Each MnIII ion is chelated by a salen type ligand (H2L), but there is variation in the bridging group: LMn(OOCCH[double bond, length as m-dash]CHCOO)MnL, LMn(OOCC6H4COO)MnL, and LMn(OOCC6H4C6H4COO)MnL. X-ray diffraction revealed an axial compression of each six-coordinate high-spin d4 MnIII ion, which is a Jahn-Teller-active ion. Temperature dependent magnetic susceptibility and variable temperature-variable field (VTVH) magnetisation measurements, as well as high-frequency and -field EPR (HFEPR) spectroscopy were used to accurately describe the magnetic properties of the complexes, not only the single-ion spin Hamiltonian parameters: g-values and zero-field splitting (ZFS) parameters D and E, but also the exchange interaction constant J between the two ions, which has been seldom determined for a di-MnIII complex, particularly when there is more than a single bridging atom. Quantum chemical calculations reproduced well the electronic and geometric structure of these unusual complexes, and, in particular, their electronic absorption spectra along with the spin Hamiltonian and exchange parameters.

16.
Dalton Trans ; 48(5): 1700-1708, 2019 Jan 29.
Artigo em Inglês | MEDLINE | ID: mdl-30623942

RESUMO

Three isostrucutral dodecanuclear clusters with the general formula [Ln12(fsa)12(µf3-OH)12(DMF)12]·nDMF (fsa2- is the dianion of 3-formylsalicylic acid; Ln = Eu 1, Gd 2, Dy 3) have been obtained from the reaction of fromylsalicyclic acid (H2fsa), tetrabutylammonium hydroxide and Ln(NO3)3·6H2O in methanol/DMF. Their structure consists of four vertex-sharing heterocubanes. Each heterocubane unit is assembled from four LnIII ions, three µ3-OH groups and one µ3-oxygen atom arising from the fsa2- carboxylato group. The photophysical properties of the europium derivative investigated at both 300 and 80 K sustain a relative intense emission obtained under low power LED excitation at 420 nm. The dysprosium derivative shows a SMM behavior with an effective energy barrier Ueff of 22.9 cm-1, while the thermodynamical properties of Gd12 confirm a large magnetocaloric effect: S(7 T) - S(0 T) = 20R = 166 J mol-1 K), typical for isotropic GdIII derivatives, with ΔS = S(7 T) - S(0 T) = 1.7R for each GdIII ion.

17.
PLoS One ; 13(7): e0198121, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29990316

RESUMO

Stable Schiff bases containing a furoxan moiety are synthesized as single regioisomers by the reaction of 3-methyl-2-oxy-furazan-4-carbaldehydewith various amino compounds at room temperature. The structures of synthesized compounds were fully characterized by multinuclear NMR spectroscopy and X-ray crystallography. The effect of synthesized Schiff bases containing a furoxan moiety on biological generation of reactive oxygen species and nitric oxide in plant tissues was investigated for the first time by fluorescence microscopy and the released NO identified as nitrite with Griess reagent. There is a good correlation between the biological generation of NO determined by fluorescence microscopy and with Griess reagent. Some of the synthesized compounds exhibited both nitric oxide and reactive oxygen species generation abilities and represent potential NO donors in plant tissues.


Assuntos
Aldeídos/síntese química , Arabidopsis/efeitos dos fármacos , Doadores de Óxido Nítrico/farmacologia , Oxidiazóis/farmacologia , Folhas de Planta/efeitos dos fármacos , Bases de Schiff/farmacologia , Aldeídos/farmacologia , Arabidopsis/química , Arabidopsis/metabolismo , Etilenodiaminas/química , Fluoresceínas/química , Corantes Fluorescentes/química , Microscopia de Fluorescência , Óxido Nítrico/agonistas , Óxido Nítrico/biossíntese , Doadores de Óxido Nítrico/síntese química , Nitritos/agonistas , Nitritos/metabolismo , Oxidiazóis/síntese química , Folhas de Planta/química , Folhas de Planta/metabolismo , Espécies Reativas de Oxigênio/agonistas , Espécies Reativas de Oxigênio/metabolismo , Bases de Schiff/síntese química , Plântula/química , Plântula/efeitos dos fármacos , Plântula/metabolismo , Sementes/crescimento & desenvolvimento , Estereoisomerismo , Sulfanilamidas/química
18.
Dalton Trans ; 47(17): 6005-6017, 2018 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-29666870

RESUMO

A new series of {FeIII2LnIII2} heterobimetallic squares of general formula [FeIII{HB(pz)3}(CN)(µ-CN)2Ln(pyim)x(NO3)2(H2O)y]2·zH2O [Ln = La (1), Gd (2), Tb (3) and Dy (4); {HB(pz)3}- = hydrotris(pyrazolyl)borate and pyim = 2-(1H-imidazol-2-yl)pyridine; x = 2, y = 0 (1), x = y = 1 (2-4) and z = 10 (1), 6 (2), 2.76 (3), 4 (4)] were synthesized by reacting the low-spin [FeIII{HB(pz)3}(CN)3]- complex anion with the preformed [LnIII(pyim)x(NO3)2(H2O)y]+ complex cation [formed in situ by mixing the lanthanide(iii) salt and the pyim ligand]. Single-crystal X-ray diffraction shows that 1-4 crystallize in the P1[combining macron] triclinic space group, 2-4 being isomorphous. In all cases, the structure comprises neutral cyanido-bridged {FeIII2LnIII2} molecular squares in which two [FeIII{HB(pz)3}(CN)3]- units act as bis-monodentate ligands towards two [LnIII(pyim)x(NO3)2(H2O)y]+ moieties through two of the three cyanide groups. The iron(iii) and lanthanide(iii) cations regularly alternate in the corners of the square and the edges are defined by the cyanide bridges. Each iron(iii) ion in 1-4 is six-coordinate in a distorted octahedral surrounding with a tridentate tris(pyrazolyl)borate ligand and three cyanide groups in an approximately C3v symmetry. The lanthanum(iii) ion in 1 is ten-coordinate in a rare distorted sphenocorona environment, while the lanthanide(iii) ions in 2-4 are all nine-coordinate with a muffin-like geometry. The values of the FeIIILnIII distances across the cyanide bridges are 5.579(1) and 5.687(1) Å (1), 5.4695(20) and 5.4781(29) Å (2), 5.4550(12) and 5.4464(14) Å (3), 5.4463(10) and 5.4478(12) Å (4). The tetranuclear units in 1-4 are further interconnected through hydrogen bonds, π-π stacking and very weak C-Hπ type interactions leading to supramolecular three-dimensional networks with different topologies. Solid-state direct-current magnetic susceptibility analyses in the temperature range 1.9-300 K reveal the occurrence of weak intra- and intermolecular antiferromagnetic interactions in 1 [JFeFe' = -2.32(3) cm-1, gFe = 2.198(4), θ = -0.650(7) K and χTIP = 266(5) × 10-6 cm3 mol-1, the Hamiltonian being defined as H = -JFeFe'SFeSFe' + gßH(SFe + SFe')] and 2 [JFeFe' = -2.06(3) cm-1, JFeGd = -0.210(4) cm-1, gFe = 2.23(1), gGd = 2.0 (fixed), θ = -0.450(5) K and χTIP = 280(5) × 10-6 cm3 mol-1]. The coexistence of the spin-orbit coupling of the low-spin iron(iii) and lanthanide(iii) ions [TbIII (3) and DyIII (4)], together with the ligand field effects, masked the visualization of the possible magnetic interactions in 3 and 4. The small antiferromagnetic couplings in 1 and 2 are in line with previously reported weak antiferromagnetic interactions for these couples of ions through single cyanide bridges.

19.
Chemistry ; 24(35): 8779-8786, 2018 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-29637648

RESUMO

The synthesis and characterization of a dinuclear bis(thiosemicarbazone) cobalt complex [Co2 L2 (NCS)2 ] is reported. This complex exhibits significant catalytic activity for hydrogen production in DMF by using triethylammonium (Et3 NHBF4 ) as the proton source. Cyclic voltammetry data allowed a maximum turnover frequency of 130 s-1 for 1 m proton concentration to be determined. The catalytic nature of the process and the production of dihydrogen were confirmed by gas analysis during controlled potential electrolysis experiments. Quantum chemical calculations show that the complex displays a ligand-assisted metal-centered reactivity and supports a catalytic mechanism involving ligand-based reduction and protonation steps followed by metal-centered processes.

20.
Dalton Trans ; 47(8): 2531-2542, 2018 Feb 20.
Artigo em Inglês | MEDLINE | ID: mdl-29384531

RESUMO

The reaction of Ph3BiCl2 with alkali salts of isonicotinic and nicotinic acids afforded Ph3Bi[O(O)CC5H4N-4]2 (1) and Ph3Bi[O(O)CC5H4N-3]2 (2), respectively, which were characterized by multinuclear NMR spectroscopy in solution, mass spectrometry and IR spectroscopy in the solid state. Their molecular structures were established by single-crystal X-ray diffraction. For both 1 and 2 the molecules contain a trigonal bipyramidal C3BiO2 core, with the phenyl groups in equatorial positions. The potential use of 1 and 2 as ditopic organometalloligands was investigated. The reaction of 1 or 2 with Me3SnCl (1 : 2 molar ratio) resulted in carboxylato ligand exchange and the formation of Me3Sn[O(O)CC5H4N-4] (3) and Me3Sn[O(O)CC5H4N-3] (4) besides Ph3BiCl2. The crystals of both 3 and 4 contain 1-D coordination polymers built through intermolecular N → Sn interactions. The treatment of Ni[S2P(OiPr)2]2 with 1 and 2, respectively, resulted, in addition to di(carboxylato)nickel(ii) derivatives, in isolation of Ph3Bi and the disulphane [(iPrO)2P(S)S]2. New coordination polymers were obtained by reacting 1 and 2 with various silver(i) salts: [Ag{Ph3Bi[O(O)CC5H4N-4]2}(OTf)] (5), [Ag{Ph3Bi[O(O)CC5H4N-3]2}(OTf)]·CH2Cl2 (6·CH2Cl2), [Ag{Ph3Bi[O(O)CC5H4N-4]2}](SbF6)·2THF (7·2THF), [Ag{Ph3Bi[O(O)CC5H4N-3]2}](SbF6)·CH2Cl2 (8·CH2Cl2) and [Ag{Ph3Bi[O(O)CC5H4N-3]2}(NO3)]·CH2Cl2 (9·CH2Cl2). The crystal structures of 5 and 6 can be described as 1-D chains linked by triflate bridges in pairs of chains and 2-D networks, respectively. Compound 7 features a 2-D grid-like topology of the network, with tecton 1 acting as a tridentate ligand through both nitrogen and one oxygen atoms. The linker 2 molecules adopt either cis (compound 6) or trans (compounds 8 and 9) conformation. Complexes 8 and 9 are 1-D chain polymers exhibiting zig-zag and wavy motifs, respectively. The dimensionality of the structures is extended by the presence of supramolecular interactions (ππ, AgAg, AgO).

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