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1.
Nanoscale ; 15(35): 14409-14422, 2023 Sep 14.
Artículo en Inglés | MEDLINE | ID: mdl-37614145

RESUMEN

Despite the great effort made in recent years on lanthanide-based ratiometric luminescent nanothermometers able to provide temperature measurements in water, their design remains challenging. We report on the synthesis and properties of efficient ratiometric nanothermometers that are based on mesoporous stellate nanoparticles (MSN) of ca. 90 nm functionalized with an acetylacetonate (acac) derivative inside the pores and loaded with ß-diketonate-Tb3+/Eu3+ complexes able to work in water, in PBS or in cells. Encapsulating a [(Tb/Eu)9(acac)16(µ3-OH)8(µ4-O)(µ4-OH)] complex (Tb/Eu ratio = 19/1 and 9/1) led to hybrid multifunctionalized nanoparticles exhibiting a Tb3+ and Eu3+ characteristic temperature-dependent luminescence with a high rate Tb3+-to-Eu3+ energy transfer. According to theoretical calculations, the modifications of photoluminescence properties and the increase in the pairwise Tb3+-to-Eu3+ energy transfer rate by about 10 times can be rationalized as a change of the coordination number of the Ln3+ sites of the complex from 7 to 8 accompanied by a symmetry evolution from Cs to C4v and a slight shortening of intramolecular Ln3+-Ln3+ distances upon the effect of encapsulation. These nanothermometers operate in the 20-70 °C range with excellent photothermal stability, cyclability and repeatability (>95%), displaying a maximum relative thermal sensitivity of 1.4% °C-1 (at 42.7 °C) in water. Furthermore, they can operate in cells with a thermal sensitivity of 8.6% °C-1 (at 40 °C), keeping in mind that adjusting the calibration for each system is necessary to ensure accurate measurements.

2.
Langmuir ; 39(10): 3610-3618, 2023 Mar 14.
Artículo en Inglés | MEDLINE | ID: mdl-36862534

RESUMEN

Although mesoporous silica nanoparticles (MSNs) have been intensively investigated, their mesostructure and formation mechanism are still a topic of debate. Here, we show that MSNS are generated at the interface of the biphasic water-surfactant-triethanolamine-tetraalkoxysilane (TAOS) quaternary system. The spontaneous microemulsification of the hydrophobic TAOS generates microdroplets and direct micelles that both determine the particle size and the pore size. We confirmed also that the dendritic morphology with conical pores is an intermediate species, which readily transforms into regular MSNs concomitantly with the collapse of the microemulsion due to the continuous consumption of TAOS. The prominent effect of the microemulsion on the mechanism growth as a primary template is thoroughly investigated and named here tetraalkoxysilane-assisted self-emulsification templating.

3.
Nanomaterials (Basel) ; 12(7)2022 Mar 29.
Artículo en Inglés | MEDLINE | ID: mdl-35407252

RESUMEN

We report the synthesis of a hybrid nanocatalyst obtained through the immobilization of bio-inspired [{Mn(bpy)(H2O)}(µ-2-MeC6H4COO)2(µ-O){Mn(bpy)(NO3)}]NO3 compound into functionalized, monodispersed, mesoporous silica nanoparticles. The in situ dual functionalization sol-gel strategy adopted here leads to the synthesis of raspberry-shaped silica nanoparticles of ca. 72 nm with a large open porosity with preferential localization of 1,4-pyridine within the pores and sulfobetaine zwitterion on the nanoparticles' periphery. These nano-objects exhibit improved catalase-mimicking activity in water thanks to the encapsulation/immobilization of the catalytic active complex and high colloidal stability in water, as demonstrated through the dismutation reaction of hydrogen peroxide.

4.
Nanomaterials (Basel) ; 11(3)2021 Mar 18.
Artículo en Inglés | MEDLINE | ID: mdl-33803710

RESUMEN

The incorporation of a luminescent probe into a nano-vector is one of the approaches used to design chemosensors and nanocargos for drug delivery and theranostics. The location of the nano-vector can be followed using fluorescence spectroscopy together with the change of environment that affects the fluorescence properties. The ligand 9-anthracene carboxylate is proposed in this study as a luminescent probe to locate two types of manganese complexes inside three series of porous nanoparticles of different composition: resol-silica, carbon-silica and pure silica. The manganese complexes are a tetranuclear MnIII cluster [MnIII4(µ-O)2(µ-AntCO2)6(bpy)2(ClO4)2] with a butterfly core, and a MnII dinuclear complex [{MnII(bpy)(AntCO2)}2(µ-AntCO2)2(µ-OH2)]. The magnetic measurements indicate that both complexes are present as dinuclear entities when incorporated inside the particles. Both the Mn complexes and the nanoparticles are luminescent. However, when the metal complexes are introduced into the nanoparticles, the luminescent properties of both are altered. The study of the fluorescence of the nanoparticles' suspensions and of the supernatants shows that MnII compounds seem to be more retained inside the particles than MnIII compounds. The resol-silica nanoparticles with MnII complexes inside is the material that presents the lowest complex leaching in ethanol.

5.
Langmuir ; 34(43): 12713-12722, 2018 10 30.
Artículo en Inglés | MEDLINE | ID: mdl-30281317

RESUMEN

The reaction between titanium alkoxides, [Ti(OR)4], and surface silanol groups is widely used to generate grafted oxo-hydroxo titanium species, whose size is difficult to control. Partial capping of the surface silanols in the presence of the masking pattern of self-repelling tetramethylammonium ions allows us to isolate surface silanol islets, on which isolated titanium ions and dimeric oxo titanium species can be generated up to 2 Ti/Si mol %. Above this loading, and up to ∼8 Ti/Si mol %, higher oligomers (trimers, hexamers, octamers, and so on) are formed, reaching the size obtained at much lower loadings (<1 Ti/Si mol %) on a nonmodified silica surface. The downsizing effect produced on our organically modified surface is monitored from the blue-shift of the charge-transfer band of the Ti(IV) ions, measured by reflectance UV-visible spectroscopy. It is also mirrored by a higher catalytic activity in cyclohexene epoxidation, revealing that it is not only the isolated Ti species that are active but also the oligomers. Regarding the latter, the smaller they are, the more active they are.

6.
Chemistry ; 24(2): 478-486, 2018 Jan 09.
Artículo en Inglés | MEDLINE | ID: mdl-29105872

RESUMEN

Mesoporous nanospheres are highly regarded for their applications in nanomedicine, optical devices, batteries, nanofiltration, and heterogeneous catalysis. In the last field, the dendritic morphology, which favors molecular diffusion, is a very important morphology known for silica, but not yet for carbon. A one-pot, easy, and scalable co-sol-gel route by using the triphasic resol-surfactant-silica system is shown to yield the topologies of dendritic and core-shell-corona mesoporous sister nanospheres by inner radial phase speciation control on a mass-transfer-limited process, depending on the relative polycondensation rates of the resol polymer and silica phases. The trick was the use of polyolamines with different catalytic activities on each hard phase polycondensation. The self-entanglement of phases is produced at the {O- , S+ , I- } organic-surfactant-inorganic interface. Mono- and biphasic mesoporous sister nanospheres of carbon and/or silica are derivatized from each mother nanospheres and called "syntaxic" because of similar sizes and mirrored morphologies. Comparing these "false twins", or yin and yang mesoporous nanospheres, functionalized by sulfonic groups provides evidence of the superiority of the dendritic topologies and the absence of a shell on the diffusion-controlled catalytic alkylation of m-cresol.

7.
Dalton Trans ; 46(8): 2699-2714, 2017 Feb 21.
Artículo en Inglés | MEDLINE | ID: mdl-28170010

RESUMEN

A family of new MnII compounds, consisting of seven dinuclear, three mononuclear, and four trinuclear ones, were synthesised using benzoic acid derivatives n-RC6H4COOH, where n-R = 2-MeO, 3-MeO, 4-MeO, or 4-tBu, and 2,2'-bipyridine (bpy) or 1,10-phenantroline (phen) as blocking ligands. The crystal structures of nine of these compounds and the magnetic studies of all of them are reported here. Each type of compound was formed depending on the presence or absence of ClO4- ions, the solvent used, and/or the presence of a small amount of water in the reaction medium. The use of the tert-buthylbenzoate ligand gave unexpected results, very likely due to the steric hindrance caused by the voluminous tBu groups. The EPR spectra of each type of compound give some peculiar features that allow its identification. Attempts to fit these spectra have been made in order to determine the ZFS parameters, D and E, of the MnII ion (for mononuclear and dinuclear systems) or of the ground state (for trinuclear systems). For trinuclear systems, the single-ion ZFS parameters estimated from those of the ground state provided a good simulation of the EPR spectra of these compounds. The EPR signals observed in each case have been rationalised according to the energy level distribution and the plausible population in the excited states. In some particular situations, the sign of DMn could be determined from the fit of the EPR spectra of the antiferromagnetic dinuclear compounds, the source of the difference between the spectra lying in the second excited state.

8.
Dalton Trans ; 45(29): 11753-64, 2016 Jul 19.
Artículo en Inglés | MEDLINE | ID: mdl-27295557

RESUMEN

Five new dinuclear Mn(iii) compounds with benzoato derivative bridges [{Mn(bpy)L}2(µ-O)(µ-n-RC6H4COO)2]X2 (n-R = 3-MeO, 4-MeO and 4-tBu, X = NO3(-) and ClO4(-)) were synthesised and characterised. According to X-ray diffraction, the X anions tend to be coordinated to the Mn ions and may occupy the place of the monodentate ligand L. Two structural isomers that only differ in one of their monodentate ligands have been obtained with the 3-MeOC6H4COO(-) bridges. For all compounds, the Mn(iii) ions display elongated octahedra with a pronounced rhombic distortion. To quantify these distortions separately, the elongation and rhombicity parameters Δ and ρ have been defined. The magnetic study shows a good relationship between the distortion of the coordination polyhedra and the zero field splitting parameters (DMn and EMn). From the magnetic data of a powder sample, it is possible to determine the sign and magnitude of DMn for ferromagnetic systems or weak antiferromagnetic systems with DMn < 0. For this kind of dinuclear compound, the R group at the meta position, the rhombic distortion of the octahedra, and large torsion angles between the Jahn-Teller axes lead to ferromagnetic interactions.

9.
Inorg Chem ; 54(21): 10111-25, 2015 Nov 02.
Artículo en Inglés | MEDLINE | ID: mdl-26484833

RESUMEN

Two new structural and functional models of the Mn-catalase with formula [{Mn(III)(bpy)(H2O)}(µ-2-MeOC6H4CO2)2(µ-O){Mn(III)(bpy)(X)}]X, where X = NO3 (1) and ClO4 (2) and bpy = 2,2'-bipyridine, were synthesized and characterized by X-ray diffraction. In both cases, a water molecule and an X ion occupy the monodentate positions. The magnetic properties of these compounds reveal a weak antiferromagnetic behavior (2J = -2.2 cm(-1) for 1 and -0.7 cm(-1) for 2, using the spin Hamiltonian H = -2J S1·S2) and negative zero-field splitting parameter DMn (-4.6 cm(-1) and -3.0 cm(-1) for 1 and 2, respectively). This fact, together with the nearly orthogonal orientation of the Jahn-Teller axes of the Mn(III) ions explain the unusual shape of χMT versus T plot at low temperature. Compound 1 presents a better catalase activity than 2 in CH3CN-H2O media, probably due to a beneficial interaction of the NO3(-) ion with the Mn complex in solution. These compounds were successfully inserted inside two-dimensional hexagonal mesoporous silica (MCM-41 type) leading to the same hybrid material ([Mn2O]@SiO2), without the X group. The manganese complex occupies approximately half of the available pore volume, keeping the silica's hexagonal array intact. Magnetic measurements of [Mn2O]@SiO2 suggest that most of the dinuclear unit is preserved, as a non-negligible interaction between Mn ions is still observed. The X-ray photoelectron spectroscopy analysis of the Mn 3s peak confirms that Mn remains as Mn(III) inside the silica. The catalase activity study of material [Mn2O]@SiO2 reveals that the complex is more active inside the porous silica, probably due to the surface silanolate groups of the pore wall. Moreover, the new material shows catalase activity in water media, while the coordination compounds are not active.


Asunto(s)
Antioxidantes/química , Biomimética , Catalasa/química , Manganeso/química , Dióxido de Silicio/química , Cristalografía por Rayos X , Dimerización , Espectroscopía de Fotoelectrones
10.
Dalton Trans ; 43(25): 9704-13, 2014 Jul 07.
Artículo en Inglés | MEDLINE | ID: mdl-24834988

RESUMEN

Clickable ligands like N,N'-bis((pyridin-2-yl)methyl)prop-2-yn-1-amine (L(1)) and N-((1-methyl-1H-imidazol-2-yl)methyl)-N-(pyridin-2-ylmethyl)prop-2-yn-1-amine (L(2)) have been used to synthesise a series of manganese(ii) complexes for grafting onto appropriate solid supports. These ligands mimic the 2-His-1-carboxylate facial chelation present in the active site of the manganese-dependent dioxygenase (MndD), while the alkyne side function allows grafting of the ligand onto an azido-functionalised support using "click chemistry" methodologies. Such synthetic analogues of the MndD crystallise in the solid state as double halide or pseudohalide-bridged dinuclear manganese(ii) complexes of the general formula [Mn2(µ-X)2X2L2] [L = L(1) with X = Cl (), Br (), and N3 (); L = L(2) with X = N3 ()]. Complexes are characterised by a weak magnetic exchange interaction between the two high-spin Mn(II) ions through the two X(-) bridges (J in the range of -0.059 to +5.30 cm(-1), H = -J·SMn1·SMn2 with SMn1 = SMn2 = 5/2). A new magneto-structural correlation of superexchange bis(µ1,1-azido)dimanganese(ii) complexes has been proposed using both structural parameters, the Mn-N-Mn bridging angle and the Mn-Nazido distance. In MeOH-EtOH solution the dimeric species are present together with few percents of mononuclear manganese(ii) complexes as evidenced by electron paramagnetic resonance (EPR) spectroscopy. Grafting the complexes onto mesoporous silica of MCM-41 type stabilises both dimers and monomers in the nanopores of the solid.


Asunto(s)
Química Clic , Complejos de Coordinación/química , Dioxigenasas/química , Manganeso/química , Dióxido de Silicio/química , Dominio Catalítico , Cristalografía por Rayos X , Espectroscopía de Resonancia por Spin del Electrón , Ligandos , Modelos Moleculares , Conformación Molecular , Técnicas de Síntesis en Fase Sólida
11.
J Am Chem Soc ; 136(13): 4869-72, 2014 Apr 02.
Artículo en Inglés | MEDLINE | ID: mdl-24635512

RESUMEN

Stabilization of oil/oil Pickering emulsions using robust and recyclable catalytic amphiphilic silica nanoparticles bearing alkyl and propylsulfonic acid groups allows fast and efficient solvent-free acetalization of immiscible long-chain fatty aldehydes with ethylene glycol.


Asunto(s)
Emulsiones/química , Nanopartículas/química , Aceites/química , Dióxido de Silicio/química , Tensoactivos/química , Aldehídos/química , Alquilación , Catálisis , Glicol de Etileno/química , Ácidos Sulfónicos/química
12.
Dalton Trans ; 42(32): 11607-13, 2013 Aug 28.
Artículo en Inglés | MEDLINE | ID: mdl-23824307

RESUMEN

A mixed amine pyridine polydentate Fe(II) complex was covalently tethered in hexagonal mesoporous silica of the MCM-41 type. Metal site isolation was generated using adsorbed tetramethylammonium cations acting as a patterned silanol protecting mask and trimethylsilylazane as a capping agent. Then, the amine/pyridine ligand bearing a tethering triethoxysilane group was either grafted to such a pretreated silica surface prior to or after complexation to Fe(II). These two synthetic routes, denoted as two-step and one-step, respectively, were also applied to fumed silica for comparison, except that the silanol groups were capped after tethering the metal unit. The coordination of the targeted complex was monitored using UV-visible spectrophotometry and, according to XPS, the best control was achieved inside the channels of the mesoporous silica for the two-step route. For the solid prepared according to the one-step route, tethering of the complex occurred mainly at the entrance of the channel.


Asunto(s)
Materiales Biomiméticos/química , Hierro/química , Compuestos Organometálicos/química , Dióxido de Silicio/química , Aminas/química , Materiales Biomiméticos/síntesis química , Peróxido de Hidrógeno/química , Ligandos , Nanopartículas/química , Compuestos Organometálicos/síntesis química , Oxidantes/química , Porosidad
13.
Chemistry ; 19(19): 6122-36, 2013 May 03.
Artículo en Inglés | MEDLINE | ID: mdl-23512788

RESUMEN

New, ultrasmall nanoparticles with sizes below 5 nm have been obtained. These small rigid platforms (SRP) are composed of a polysiloxane matrix with DOTAGA (1,4,7,10-tetraazacyclododecane-1-glutaric anhydride-4,7,10-triacetic acid)-Gd(3+) chelates on their surface. They have been synthesised by an original top-down process: 1) formation of a gadolinium oxide Gd2O3 core, 2) encapsulation in a polysiloxane shell grafted with DOTAGA ligands, 3) dissolution of the gadolinium oxide core due to chelation of Gd(3+) by DOTAGA ligands and 4) polysiloxane fragmentation. These nanoparticles have been fully characterised using photon correlation spectroscopy (PCS), transmission electron microscopy (TEM), a superconducting quantum interference device (SQUID) and electron paramagnetic resonance (EPR) to demonstrate the dissolution of the oxide core and by inductively coupled plasma mass spectrometry (ICP-MS), mass spectrometry, fluorescence spectroscopy, (29)Si solid-state NMR, (1)H NMR and diffusion ordered spectroscopy (DOSY) to determine the nanoparticle composition. Relaxivity measurements gave a longitudinal relaxivity r1 of 11.9 s(-1) mM(-1) per Gd at 60 MHz. Finally, potentiometric titrations showed that Gd(3+) is strongly chelated to DOTAGA (complexation constant logß110 =24.78) and cellular tests confirmed the that nanoconstructs had a very low toxicity. Moreover, SRPs are excreted from the body by renal clearance. Their efficiency as contrast agents for MRI has been proved and they are promising candidates as sensitising agents for image-guided radiotherapy.


Asunto(s)
Gadolinio/química , Compuestos Heterocíclicos con 1 Anillo/química , Dióxido de Silicio/química , Siloxanos/química , Sustancia P/análogos & derivados , Medios de Contraste/química , Imagen por Resonancia Magnética/métodos , Espectroscopía de Resonancia Magnética , Microscopía Electrónica de Transmisión , Nanopartículas/química , Radioterapia Guiada por Imagen , Espectrometría de Fluorescencia , Sustancia P/química
14.
J Am Chem Soc ; 135(7): 2427-30, 2013 Feb 20.
Artículo en Inglés | MEDLINE | ID: mdl-23363241

RESUMEN

Mesoporous silica nanoparticles (MSNs) are experiencing rapid development in the biomedical field for imaging and for use in heterogeneous catalysis. Although the synthesis of MSNs with various morphologies and particle sizes has been reported, synthesis of a pore network with monodispersion control below 200 nm is still challenging. We achieved this goal using mild conditions. The reaction occurred at atmospheric pressure with a templating sol-gel technique using cetyltrimethylammonium (CTA(+)) as the templating surfactant and small organic amines (SOAs) as the mineralizing agent. Production of small pore sizes was performed for the first time, using pure and redispersible monodispersed porous nanophases with either stellate (ST) or raspberry-like (RB) channel morphologies. Tosylate (Tos(-)) counterions favored ST and bromide (Br(-)) RB morphologies at ultralow SOA concentrations. Both anions yielded a worm-like (WO) morphology at high SOA concentrations. A three-step formation mechanism based on self-assembly and ion competition at the electrical palisade of micelles is proposed. Facile recovery and redispersion using specific SOAs allowed a high yield production at the kilogram scale. This novel technique has practical applications in industry.

15.
Dalton Trans ; 42(5): 1530-5, 2013 Feb 07.
Artículo en Inglés | MEDLINE | ID: mdl-23138197

RESUMEN

Three copper(II)@hemicryptophane complexes with various cavity sizes and shapes, Cu(II)@1, Cu(II)@2 and Cu(II)@3, were synthesized and characterized by near-IR/vis and EPR spectroscopies. The spectroscopic data are consistent with the presence of a trigonal-bipyramidal geometry of the N(4)Cu·H(2)O core, in accord with the energy-minimized structures obtained from DFT calculations. Cyclic voltammetry studies in CH(2)Cl(2) showed irreversible redox processes, whereas electrolysis coulometry indicated that Cu(II)/Cu(I) complexes could be interconverted. Electrochemistry data of the complexes stress the crucial role of the cage structure of the hemicryptophane in the thermodynamics of the electron transfer.


Asunto(s)
Complejos de Coordinación/química , Compuestos Policíclicos/síntesis química , Complejos de Coordinación/síntesis química , Cobre/química , Técnicas Electroquímicas , Espectroscopía de Resonancia por Spin del Electrón , Transporte de Electrón , Electrones , Modelos Moleculares , Oxidación-Reducción , Compuestos Policíclicos/química , Termodinámica
16.
Chemistry ; 17(50): 14258-66, 2011 Dec 09.
Artículo en Inglés | MEDLINE | ID: mdl-22068981

RESUMEN

Following the structural concept of copper-containing proteins in which dinuclear copper centers are connected by hydroxide bridging ligands, a bidentate copper(II) complex has been incorporated into nano-confined MCM-41 silica by a multistep sequential grafting technique. Characterization by a combination of EPR spectroscopy, X-ray photoelectron spectroscopy (XPS), UV/Vis spectroscopy, IR spectroscopy , and solid-state (13)C and (29)Si cross-polarization magic-angle spinning (CP-MAS) NMR suggests that dinuclear Cu complexes are bridged by hydroxide and other counterions (chloride or perchlorate ions), similar to the situation for EPR-undetectable [Cu(II)···Cu(II)] dimer analogues in biological systems. More importantly, a dynamic mononuclear-dinuclear equilibrium between different coordination modes of copper is observed, which strongly depends on the nature of the counterions (Cl(-) or ClO(4)(-)) in the copper precursor and the pore size of the silica matrix (the so-called confinement effect). A proton-transfer mechanism within the hydrogen-bonding network is suggested to explain the dynamic nature of the dinuclear copper complex supported on the MCM-41 silica.


Asunto(s)
Cobre/química , Compuestos Organometálicos/química , Dióxido de Silicio/química , Catálisis , Cristalografía por Rayos X , Enlace de Hidrógeno , Espectroscopía de Resonancia Magnética , Conformación Molecular , Espectroscopía de Fotoelectrones , Protones , Espectrofotometría Ultravioleta
17.
Langmuir ; 26(16): 13493-501, 2010 Aug 17.
Artículo en Inglés | MEDLINE | ID: mdl-20695596

RESUMEN

The accessibility of metal(II) complexes in 2D hexagonal mesostructured porous silicas obtained by direct synthesis is controlled using an appropriate organosilane ligand. This is exemplified here using copper(II) as a transition metal probe and a neutral or negatively charged ligand: N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, L(A), and, N-salicylaldimine-propylamine-trimethoxysilane, L(B)(-), respectively. L(A) leads to inaccessible complexes located into the pore wall and called "embedded" sites here where silanolate groups from the siliceous network block the access to Cu(II) ions. By contrast, L(B)(-) generates accessible complexes, named "showing-on" sites here. The copper-containing silicas were synthesized with various metal molar ratios (M/SiO(2) = 0.5-3%) in basic media, with cetyltrimethylammonium p-toluenesulfonate (CTATos) as template and with sodium silicate solution as silicon source. A soft template extraction procedure has been developed to preserve the complex integrity of the showing-on copper sites during the treatment. The embedded copper(II) and nickel(II) sites were compared. Materials containing embedded, showing-on, and grafted sites were also compared with regard to pore size, surface polarity, and metal leaching. The material containing showing-on sites was found to be catalytically active for the hydroxylation of phenol into catechol and hydroquinone. Both textural and structural properties of the material and the copper sites were investigated using XRD, TEM, N(2) sorption isotherms, TGA, FT-IR, UV-visible, and EPR spectroscopies.

18.
Phys Chem Chem Phys ; 11(16): 2912-21, 2009 Apr 28.
Artículo en Inglés | MEDLINE | ID: mdl-19421506

RESUMEN

The molecular stencil patterning (MSP) technique is a new surface molecular engineering technique developed for cation-templated porous silicas to graft several functions with vicinity control. First, tetramethylammonium ions (TMA(+)) are introduced by ion exchange of the cetyltrimethyl-ammonium template (CTA(+)). Then, the coverage is controlled to create a masking array of cations, the pattern of which is produced by mutual electrostatic repulsion. A first function is grafted, here monopodal trimethylsilyl groups (TMS) or dipodal ethyl-1,2-bis(dimethylsilyl) (EBDMS) groups. After the removal of the masking cations, a second function is grafted using here N-(2-aminoethyl)-3-amino-propyltrimethoxysilane precursor. The distribution of N-(2-aminoethyl)-3-amino-propylsilyl functions (AAPS) is probed by complexation to Cu(ii) ions. X-Ray diffraction, N(2) adsorption-desorption isotherms, (13)C solid-state NMR, IR, UV-visible and electron paramagnetic resonance (EPR) techniques show that MSP can produce isolation of AAPS by TMS, or even better by EBDMS groups, with preservation of the silica pore structure.

19.
Inorg Chem ; 44(20): 6959-66, 2005 Oct 03.
Artículo en Inglés | MEDLINE | ID: mdl-16180857

RESUMEN

Two manganese complexes, (py2(NMe)2)MnIICl2 (1) and [(py2(NMe)2)MnIIIF2]+ (2), are here described with the macrocyclic ligand py2(NMe)2 (py2(NMe)2 = N,N'-dimethyl-2,11-diaza[3,3](2,6)pyridinophane). For both, the crystal structure is reported. The UV-visible spectrum of 2 exhibits a very broad near-infrared (NIR) band corresponding to the transition between the two e(g)-type orbitals split by the Jahn-Teller effect. A negative D value of ca. -4 cm(-1) was estimated by high-field and high-frequency electron paramagnetic resonance (HF-EPR) spectroscopy, which was consistent with symmetry considerations. Density functional theory (DFT) calculations on 2 support the 5B1 electronic ground state predicted from the X-ray structure. Moreover, to explain the large value of the D parameter, a spin triplet first excited spin state was postulated to occur at low energy. This was confirmed by the DFT calculations.


Asunto(s)
Compuestos Aza/química , Cloruros/química , Compuestos de Manganeso/química , Manganeso , Piridinas/química , Compuestos Aza/síntesis química , Espectroscopía de Resonancia por Spin del Electrón/métodos , Modelos Moleculares , Piridinas/síntesis química , Difracción de Rayos X
20.
Inorg Chem ; 38(22): 5131-5138, 1999 Nov 01.
Artículo en Inglés | MEDLINE | ID: mdl-11671260

RESUMEN

The mononuclear blue complex [Ru(III)L] (1) where L represents the trianion of 1,4,7-tris(4-tert-butyl-2-mercaptobenzyl)-1,4,7-triazacyclononane has been synthesized by the reaction of H(3)L.3HPF(6) with [Ru(II)Cl(2)(dmso)(4)] in refluxing CH(3)OH in the presence of air. Chemical or electrochemical oxidation of 1 generates [Ru(II)(2)(L-L)](PF(6))(4) (2), a dinuclear species containing two Ru(II) ions and a neutral tris(disulfide) ligand L-L. The reaction of 1 with 1 equiv of [Ru(II)Cl(2)(dmso)(4)] produces the trinuclear species [LRuRuRuL](PF(6))(2) (3) in low yield. Complexes 2 and 3 have been structurally characterized by X-ray crystallography: [Ru(II)(2)(L-L)](BPh(4))(4).10CH(3)CN, C(194)H(218)B(4)N(16)Ru(2)S(6), crystallizes in the monoclinic space group C2/c with a = 28.734(5) Å, b = 16.347(3) Å, c = 37.986(7) Å, beta = 102.35(2) degrees, and Z = 4 whereas [LRuRuRuL](PF(6))(2).H(2)O, C(78)H(110)F(12)N(6)OP(2)Ru(3)S(6), crystallizes in the monoclinic space group P2(1)/n with a = 18.755(4) Å, b = 22.278(4) Å, c = 21.920(4) Å, beta = 91.69(3) Å, and Z = 4. The electro- and spectroelectrochemistry of 1-3 have been studied in detail as have their electronic structures by (1)H NMR, EPR, UV-vis, IR, and Raman spectroscopy.

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