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1.
Pediatrics ; 153(4)2024 Apr 01.
Artículo en Inglés | MEDLINE | ID: mdl-38516717

RESUMEN

OBJECTIVE: To test efficacy of a parent-delivered multidomain early intervention (Learning through Everyday Activities with Parents [LEAP-CP]) for infants with cerebral palsy (CP) compared with equal-dose of health advice (HA), on (1) infant development; and (2) caregiver mental health. It was hypothesized that infants receiving LEAP-CP would have better motor function, and caregivers better mental health. METHODS: This was a multisite single-blind randomized control trial of infants aged 12 to 40 weeks corrected age (CA) at risk for CP (General Movements or Hammersmith Infant Neurologic Examination). Both LEAP-CP and HA groups received 15 fortnightly home-visits by a peer trainer. LEAP-CP is a multidomain active goal-directed intervention. HA is based on Key Family Practices, World Health Organization. Primary outcomes: (1) infants at 18 months CA: Pediatric Evaluation of Disability Inventory-Computer Adaptive Test (PEDI-CAT mobility); and (2) caregiver: Depression Anxiety and Stress Scale. RESULTS: Of eligible infants, 153 of 165 (92.7%) were recruited (86 males, mean age 7.1±2.7 months CA, Gross Motor Function Classification System at 18 m CA: I = 12, II = 25, III = 9, IV = 18, V = 32). Final data were available for 118 (77.1%). Primary (PEDI-CAT mobility mean difference = 0.8 (95% CI -1.9 to 3.6) P = .54) and secondary outcomes were similar between-groups. Modified-Intention-To-Treat analysis on n = 96 infants with confirmed CP showed Gross Motor Function Classification System I and IIs allocated to LEAP-CP had significantly better scores on PEDI-CAT mobility domain (mean difference 4.0 (95% CI = 1.4 to 6.5), P = .003) compared with HA. CONCLUSIONS: Although there was no overall effect of LEAP-CP compared with dose-matched HA, LEAP-CP lead to superior improvements in motor skills in ambulant children with CP, consistent with what is known about targeted goal-directed training.


Asunto(s)
Parálisis Cerebral , Niño , Humanos , Lactante , Masculino , Cuidadores , Parálisis Cerebral/terapia , Países en Desarrollo , Movimiento , Método Simple Ciego
2.
Front Public Health ; 11: 1269444, 2023.
Artículo en Inglés | MEDLINE | ID: mdl-38222087

RESUMEN

Musculoskeletal disorders are debilitating conditions that significantly impact the state of health, especially in older people. The study, which employed a cross-sectional design and practical sampling, included 206 participants among them 124 (62.2%) were men and 82 (39.8%) were women, from all over Bangladesh with musculoskeletal issues of varying severity and impact. The mean age of the participants was 64.9 (SD 4.3). The study was carried out between January and June of 2022. The majority of participants experienced musculoskeletal pain. Back pain was the most commonly complained of symptom among the participants (74.9%). It was also common to have limited mobility as a result of arthritic change, which eventually affected daily activities like taking care of oneself. To improve the health of the older adult population, more studies must be conducted to identify the many factors that contribute to musculoskeletal issues. The development of effective prevention and rehabilitation programs must then be based on this knowledge.


Asunto(s)
Enfermedades Musculoesqueléticas , Calidad de Vida , Masculino , Humanos , Femenino , Anciano , Estudios Transversales , Bangladesh/epidemiología , Enfermedades Musculoesqueléticas/epidemiología , Enfermedades Musculoesqueléticas/prevención & control , Comorbilidad
3.
Inorg Chem ; 61(17): 6660-6671, 2022 May 02.
Artículo en Inglés | MEDLINE | ID: mdl-35446020

RESUMEN

Synthesizing hydrosulfido Cu thiolate complexes is quite challenging. In this report, two new and rare hydrosulfido Cu thiolate complexes, [Et4N]2[(mnt)Cu-SH] (2, mnt = maleonitrile dithiolene = S2C2(CN)2) and [Et4N]3[(mnt)Cu-(µ-SH)-Cu(mnt)] (3), have been synthesized. Coordination sites and O2 activation by complex 2 resemble the formylglycine generating enzyme (FGE), an enzyme recently crystallographically characterized with sulfur-only coordination around Cu (three thiolate ligands). The function of this enzyme (and complex 2) is surprising because vulnerable thiolates should not be well suited for O2 activation rationally. Indeed, activation of oxygen by such an all-sulfur-coordinated Cu complex 2 is lacking in the literature. Aerial O2 (ambient O2 from the air) activation by complex 2 could proceed through a superoxide radical intermediate and a sulfur radical intermediate detected by resonance Raman (rR) spectroscopy and electron paramagnetic resonance (EPR) spectroscopy, respectively. The chemistry of 2 has been examined by its reactivity, crystal structure, and spectroscopic and cyclic voltammetric analyses. In addition, the results have been complemented with density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations.


Asunto(s)
Cobre , Oxígeno , Cobre/química , Espectroscopía de Resonancia por Spin del Electrón , Glicina/análogos & derivados , Ligandos , Oxígeno/química , Azufre/química
4.
Angew Chem Int Ed Engl ; 60(29): 15792-15797, 2021 07 12.
Artículo en Inglés | MEDLINE | ID: mdl-33928749

RESUMEN

Constructing synthetic models of the nitrogenase PN -cluster has been a long-standing synthetic challenge. Here, we report an optimal nitrogenase PN -cluster model [{(TbtS)(OEt2 )Fe4 S3 }2 (µ-STbt)2 (µ6 -S)] (2) [Tbt=2,4,6-tris{bis(trimethylsilyl)methyl}phenyl] that is the closest synthetic mimic constructed to date. Of note is that two thiolate ligands and one hexacoordinated sulfide are connecting the two Fe4 S3 incomplete cubanes similar to the native PN -cluster, which has never been achieved. Cluster 2 has been characterized by X-ray crystallography and relevant physico-chemical methods. The variable temperature magnetic moments of 2 indicate a singlet ground state (S=0). The Mössbauer spectrum of 2 exhibits two doublets with an intensity ratio of 3:1, which suggests the presence of two types of iron sites. The synthetic pathway of the cluster 2 could indicate the native PN -cluster maturation process as it has been achieved from the Fe4 S4 cubane Fe4 S4 (STbt)4 (1).


Asunto(s)
Compuestos Férricos/química , Compuestos Férricos/síntesis química , Hierro/química , Nitrogenasa/química , Azufre/química , Técnicas de Química Sintética , Ligandos , Modelos Moleculares , Conformación Molecular
5.
Sci Rep ; 9(1): 17027, 2019 Nov 19.
Artículo en Inglés | MEDLINE | ID: mdl-31745221

RESUMEN

Current research on catalysts for proton exchange membrane fuel cells (PEMFC) is based on obtaining higher catalytic activity than platinum particle catalysts on porous carbon. In search of a more sustainable catalyst other than platinum for the catalytic conversion of water to hydrogen gas, a series of nanoparticles of transition metals viz., Rh, Co, Fe, Pt and their composites with functionalized graphene such as RhNPs@f-graphene, CoNPs@f-graphene, PtNPs@f-graphene were synthesized and characterized by SEM and TEM techniques. The SEM analysis indicates that the texture of RhNPs@f-graphene resemble the dispersion of water droplets on lotus leaf. TEM analysis indicates that RhNPs of <10 nm diameter are dispersed on the surface of f-graphene. The air-stable NPs and nanocomposites were used as electrocatalyts for conversion of acidic water to hydrogen gas. The composite RhNPs@f-graphene catalyses hydrogen gas evolution from water containing p-toluene sulphonic acid (p-TsOH) at an onset reduction potential, Ep, -0.117 V which is less than that of PtNPs@f-graphene (Ep, -0.380 V) under identical experimental conditions whereas the onset potential of CoNPs@f-graphene was at Ep, -0.97 V and the FeNPs@f-graphene displayed onset potential at Ep, -1.58 V. The pure rhodium nanoparticles, RhNPs also electrocatalyse at Ep, -0.186 V compared with that of PtNPs at Ep, -0.36 V and that of CoNPs at Ep, -0.98 V. The electrocatalytic experiments also indicate that the RhNPs and RhNPs@f-graphene are stable, durable and they can be recycled in several catalytic experiments after washing with water and drying. The results indicate that RhNPs and RhNPs@f-graphene are better nanoelectrocatalysts than PtNPs and the reduction potentials were much higher in other transition metal nanoparticles. The mechanism could involve a hydridic species, Rh-H- followed by interaction with protons to form hydrogen gas.

6.
BMJ Open ; 8(6): e021186, 2018 06 22.
Artículo en Inglés | MEDLINE | ID: mdl-29934387

RESUMEN

INTRODUCTION: Cerebral palsy (CP) is the most common childhood physical disability, with 80% estimated to be in low-middle-income countries. This study aims to (1) determine the accuracy of General Movements (GMs)/Hammersmith Infant Neurological Examination (HINE) for detecting CP at 18 months corrected age (CA); (2) determine the effectiveness of a community-based parent-delivered early intervention for infants at high risk of CP in West Bengal, India (Learning through Everyday Activities with Parents for infants with CP; LEAP-CP). METHODS: This study comprises two substudies: (1) a study of the predictive validity of the GMs and HINE for detecting CP; (2) randomised, double-blinded controlled trial of a novel intervention delivered through peer trainers (Community Disability Workers, CDW) compared with health advice (15 fortnightly visits). 142 infants at high risk of CP ('absent fidgety' GMs; 'high risk score' on HINE) aged 12-40 weeks CA will be recruited to the intervention substudy, with infants randomised based on a computer-generated sequence. Researchers will be masked to group allocation, and caregivers and CDWs naïve to intervention status. Visits will include therapeutic modules (goal-directed active motor/cognitive strategies and LEAP-CP games) and parent education. Health advice is based on the Integrated Management of Childhood Illness, WHO. Infants will be evaluated at baseline, post intervention and 18 months CA. The primary hypothesis is that infants receiving LEAP-CP will have greater scaled scores on the Pediatric Evaluation of Disability Inventory-Computer Adaptive Test (mobility domain) at 18 months compared with health advice. Secondary outcomes include infant functional motor, cognitive, visual and communication development; infant growth; maternal mental health. ETHICS AND DISSEMINATION: This study is approved through appropriate Australian and Indian ethics committees (see in text) with families providing written informed consent. Findings from this trial will be disseminated through peer-reviewed journal publications and conference presentations. TRIAL REGISTRATION NUMBER: 12616000653460p; Pre-results.


Asunto(s)
Parálisis Cerebral/terapia , Servicios de Salud Comunitaria/organización & administración , Intervención Médica Temprana/métodos , Objetivos , Países en Desarrollo , Método Doble Ciego , Ambiente , Recursos en Salud , Humanos , India , Lactante , Evaluación de Resultado en la Atención de Salud , Padres/educación , Ensayos Clínicos Pragmáticos como Asunto
7.
Angew Chem Int Ed Engl ; 57(36): 11594-11597, 2018 Sep 03.
Artículo en Inglés | MEDLINE | ID: mdl-29775229

RESUMEN

An unprecedented, super oxidized all-ferric iron-sulfur cubanoid cluster with all terminal thiolates, Fe4 S4 (STbt)4 (3) [Tbt=2,4,6-tris{bis(trimethylsilyl)methyl}phenyl], has been isolated from the reaction of the bis-thiolate complex Fe(STbt)2 (2) with elemental sulfur. This cluster 3 has been characterized by X-ray crystallography, zero-field 57 Fe Mössbauer spectroscopy, cyclic voltammetry, and other relevant physico-chemical methods. Based on all the data, the electronic ground state of the cluster has been assigned to be Stot =0.

8.
Sci Rep ; 7(1): 16948, 2017 12 05.
Artículo en Inglés | MEDLINE | ID: mdl-29208921

RESUMEN

The development of alternate catalysts that utilize non-precious metal based electrode materials such as the first row transition metal complexes is an important goal for economic fuel cell design. In this direction, a new Fe4S4 cubane type cluster, [PPh4]2[Fe4S4(DMET)4] (1) (DMET = cis-1,2-dicarbomethoxyethylene dithiolate) and its composite with functionalized graphene, (1@graphene) have been synthesized and characterized. The presence of nanocrystalline structures on graphene matrix in TEM and SEM images of 1@graphene indicate that the cluster (1) has been immobilized. The composite, 1@graphene evolves H2 gas from p-toluene sulfonic acid (TsOH) in a mixture of H2O and CH3CN under ambient conditions with a significant turnover number of 3200. 1@graphene electro-catalyzes H2 evolution at Ep, -1.2 V with remarkable throughput, catalytic efficiency and stability in only H2O or in only CH3CN. The Fe4S4 cluster (1) alone electro-catalyzes hydrogen evolution at Ep, -0.75 V from TsOH in CH3CN. The X-ray crystal structure of the Fe4S4 cluster (1) (λmax, CH2Cl2, 823 nm; ε, 2200 mol-1 cm-1) shows that it is dianionic with a cumulative oxidation state of +2.5 for the iron centers and short C-S bond distances (ca., 1.712 Å & 1.727 Å) indicating the presence of sulfur based radicals.

9.
Inorg Chem ; 53(1): 6-8, 2014 Jan 06.
Artículo en Inglés | MEDLINE | ID: mdl-24320705

RESUMEN

[Et4N]2[Mo(IV)O(mnt)2] (mnt = maleonitriledithiolate) reacts, as a synthon, with Me3SiCN under an acidic medium to produce the square complex [Et4N]4[Mo4(µ-CN)4(mnt)8] (1) in high yield. Complex 1 shows strong antiferromagnetic interactions between adjacent Mo atoms in the cluster. The presence of redox-active mnt as a capping ligand strongly influences the magnetic property of 1. The physicochemical properties of 1 have been rationalized by density functional theory level of calculations.

10.
Inorg Chem ; 52(9): 5316-27, 2013 May 06.
Artículo en Inglés | MEDLINE | ID: mdl-23594155

RESUMEN

Three new complexes, [Mo(IV)O(mnt)(SS)](2-) (SS = dimethylethylenedicarboxylate (DMED), toluenedithiolate (tdt), benzenedithiolate (bdt); mnt = maleonitriledithiolate), each possessing two different dithiolene ligands, are synthesized as model of trimethylamine-N-oxide reductase. The asymmetric dithiolene ligands present in these complexes simulate the two different (P and Q) pterin coordinations in the family of DMSO reductase. These complexes reduce trimethylamine-N-oxide ((CH3)3N(+)-O(-) or TMANO), the biological substrate of trimethylamine-N-oxide reductase, to trimethylamine ((CH3)3N), responsible for the fishy smell of dead aquatic animals. The reaction kinetics of trimethylamine-N-oxide reduction by these complexes follow the Michaelis-Menten saturation kinetics. These experimental findings have been rationalized by DFT, TD-DFT level of calculations.


Asunto(s)
Complejos de Coordinación/química , Sistema Enzimático del Citocromo P-450/química , Metilaminas/química , Molibdeno/química , Shewanella/enzimología , Derivados del Benceno/química , Ácidos Carboxílicos/química , Cristalografía por Rayos X , Etilenos/química , Modelos Moleculares , Oxidación-Reducción , Oxígeno/química , Teoría Cuántica , Compuestos de Sulfhidrilo/química , Tolueno/análogos & derivados
11.
Chem Asian J ; 8(6): 1128-38, 2013 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-23589528

RESUMEN

Fe-W heterometallic complexes, in which an FeX2 (X = Cl, SPh) moiety is attached to monodithiolene oxotungsten through a sulfide bridge, that is, [Ph4P]2[Cl2Fe(S)2WOS2] (1), [Ph4P]2[Cl2Fe(S)2WOS2(DMED)] (2, DMED = dimethylethylenedicarboxylate), [Ph4P]2[Cl2Fe(S)2WO(tdt)] (3, tdt = toluenedithiolate), [Ph4P]2[(SPh)2Fe(S)2WO(tdt)] (4), and [Ph4P]2[Cl2Fe(S)2WO(edt)] (5, edt = ethanedithiolate), are reported. Mössbauer and EPR spectroscopy, magnetism, electrochemistry, and electronic structural analysis based on DFT and TD-DFT calculations show the transfer of electron from the iron center to the tungsten center, thus resulting in a ferromagnetically coupled Fe(III) W(V) unit, along with antiferromagnetic intermolecular interactions, from the starting Fe(II) and W(VI) compounds. A net spin of a S = 3 ground state, which arises from ferromagnetically coupled Fe(III) and W(V) atoms, displays a rare X-band EPR in normal mode at g ≈ 7 in the solid state.


Asunto(s)
Hierro/química , Compuestos Organometálicos/química , Compuestos de Sulfhidrilo/química , Tungsteno/química , Cristalografía por Rayos X , Reacción de Cicloadición , Transporte de Electrón , Magnetismo , Modelos Químicos , Modelos Moleculares , Compuestos Organometálicos/síntesis química , Espectroscopía de Mossbauer
12.
Dalton Trans ; 41(41): 12926-35, 2012 Nov 07.
Artículo en Inglés | MEDLINE | ID: mdl-22990599

RESUMEN

Mo-Fe heterometallic complexes with Fe(X)(2) (X = Cl, SPh) moiety attached to monodithiolene oxomolybdenum via sulfur bridge, viz., [Ph(4)P](2)[Cl(2)FeS(2)MoOS(2)(DMED)] (2) (DMED, dimethylethylenedicarboxylate), [Ph(4)P](2)[Cl(2)FeS(2)MoO(tdt)] (3) (tdt, toluenedithiolate) and [Ph(4)P](2)[(SPh)(2)FeS(2)MoO(tdt)] (4) are reported. Mossbauer spectroscopy, magnetism, EPR, electrochemistry and electronic structure based on DFT and TD-DFT calculation show the transfer of electron from iron to molybdenum centre resulting antiferromagnetically coupled Fe(III)Mo(V) unit from the starting Fe(II) and Mo(VI) compounds. A net spin of S = 2 ground state arising from antiferromagnetically coupled Fe(III) and Mo(V) shows a rare X-band EPR in normal mode at g ~ 12 in the solid state. In addition, Mossbauer studies show that electron drifting is more pronounced upon substitution of the chloride ligand by thiophenolate. The changes in dithiolene periphery electronically affect the charge distribution between Mo-Fe in {OMo(µS)(2)Fe} core. DFT calculations indicate that the increasing stability of dative Fe → Mo hetero metal-metal bond in these complexes from 3 to 2 to 4 is related to the extent of electron transfer from the iron to molybdenum centre.


Asunto(s)
Hierro/química , Molibdeno/química , Compuestos Organometálicos/química , Azufre/química , Cristalografía por Rayos X , Fenómenos Magnéticos
13.
Chem Biodivers ; 9(9): 1867-79, 2012 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-22976976

RESUMEN

Mono(maleonitriledithiolene)sulfidomolybdenum(IV) complex, [MoS(S(4))(mnt)](2-) (2; mnt=maleonitriledithiolene) was synthesized by the substitution reaction of a tetrasulfido ligand of the known [MoS(S(4))(2)](2-) (1) upon reaction with one or even excess equivalent of Na(2)(mnt) in aqueous MeCN solution in air. Surprisingly, 2 undergoes dimerization on treatment with alkyl halide such as MeI and PhCH(2)Br to form bis(µ-sulfido)dimolybdenum(V) species, [{MoS(mnt)}(2)(µ-S)(2)](2-) (3). These complexes have been characterized by IR, UV/VIS spectroscopy, cyclic voltammetry, elemental analysis, and by X-ray crystal-structure analysis. Differences in the relative stability and electrochemical behavior of 1, 2, and 3 have been correlated with theoretical calculations at DFT level.


Asunto(s)
Molibdeno/química , Compuestos Organometálicos/síntesis química , Teoría Cuántica , Compuestos de Sulfhidrilo/química , Cristalografía por Rayos X , Modelos Moleculares , Compuestos Organometálicos/química , Oxidación-Reducción , Análisis Espectral
14.
Chemphyschem ; 13(5): 1240-5, 2012 Apr 10.
Artículo en Inglés | MEDLINE | ID: mdl-22383264

RESUMEN

Dithiobisphthalimide is used as a new precursor for the spontaneous deposition of sulfur on gold surfaces in acetonitrile. Characterization of the modified surfaces is achieved using X-ray photoelectron spectroscopy (XPS), electrochemistry and scanning tunneling microscopy (STM). The reported results indicate that the sulfur deposition is an efficient and fast process and that high coverages can be reached very quickly. Sequential high-resolution STM in air allows the direct observation, for the first time, of the mobility of the usually observed rectangular structures as individual units. It also shows the reversible association/dissociation of these rectangles. The nature of these structures is highly debated in the literature and the present work provides new insights into their nature through the use of a new sulfur precursor under non-traditional conditions. To explain our results we consider these structures as simple sulfur adlayers on the gold surface.

15.
Dalton Trans ; 41(12): 3536-40, 2012 Mar 28.
Artículo en Inglés | MEDLINE | ID: mdl-22314336

RESUMEN

A super reduced Fe(4)S(4) cluster with a sulfur based radical, [NBu(4)](4)[Fe(3)(III)Fe(II)(µ(3)-S)(4)(mnt)(3)(6-)(mnt)(1-)˙](4-)˙, (1) (mnt, maleonitrile dithiolate) which evolves H(2)S gas on treatment with acid under ambient conditions has been synthesized and structurally characterized. The Fe-S distances in 1 are in the range 2.246-2.383 Å, in stark contrast to that of the known n = -2 member of the series based on the [Fe(4)(µ(3)-S)(4)(S(2)C(2)R(2))(4)](n) unit (R = CF(3), Ph) with Fe-S bond lengths of 2.149-2.186 Å. The EPR of 1 displays very weak signals at g, 4.03 and 2.38 along with a strong S-based radical EPR signal at g, 2.003 associated with five structured components tentatively assigned to hyperfine interaction arising out of the naturally abundant (57)Fe with = 88 G. The EPR profile resembles the reduced Fe-S cluster of CO inhibited Clostridium pasteurianum W5 hydrogenase or the Fe(4)S(4) centers of wild-type enzyme, IspH treated with HMBPP or IPP.


Asunto(s)
Compuestos Ferrosos/química , Proteínas Hierro-Azufre/química , Compuestos Organometálicos/química , Compuestos de Sulfhidrilo/química , Transferasas Alquil y Aril/química , Clostridium/enzimología , Espectroscopía de Resonancia por Spin del Electrón , Hidrogenasas/química , Indoles/metabolismo , Modelos Químicos , Estructura Molecular , Organofosfatos/metabolismo
16.
J Am Chem Soc ; 133(39): 15434-43, 2011 Oct 05.
Artículo en Inglés | MEDLINE | ID: mdl-21863869

RESUMEN

Hydrogen is the ideal fuel because it contains the most energy per gram of any chemical substance and forms water as the only byproduct of consumption. However, storage still remains a formidable challenge because of the thermodynamic and kinetic issues encountered when binding hydrogen to a carrier. In this study, we demonstrate how the principal binding sites in a new class of hydrogen storage materials based on the Kubas interaction can be tuned by variation of the coordination sphere about the metal to dramatically increase the binding enthalpies and performance, while also avoiding the shortcomings of hydrides and physisorpion materials, which have dominated most research to date. This was accomplished through hydrogenation of chromium alkyl hydrazide gels, synthesized from bis(trimethylsilylmethyl) chromium and hydrazine, to form materials with low-coordinate Cr hydride centers as the principal H(2) binding sites, thus exploiting the fact that metal hydrides form stronger Kubas interactions than the corresponding metal alkyls. This led to up to a 6-fold increase in storage capacity at room temperature. The material with the highest capacity has an excess reversible storage of 3.23 wt % at 298 K and 170 bar without saturation, corresponding to 40.8 kg H(2)/m(3), comparable to the 2015 DOE system goal for volumetric density (40 kg/m(3)) at a safe operating pressure. These materials possess linear isotherms and enthalpies that rise on coverage, retain up to 100% of their adsorption capacities on warming from 77 to 298 K, and have no kinetic barrier to adsorption or desorption. In a practical system, these materials would use pressure instead of temperature as a toggle and can thus be used in compressed gas tanks, currently employed in the majority of hydrogen test vehicles, to dramatically increase the amount of hydrogen stored, and therefore range of any vehicle.

17.
Inorg Chem ; 50(9): 3852-4, 2011 May 02.
Artículo en Inglés | MEDLINE | ID: mdl-21452808

RESUMEN

The synthesis, crystal structure, and spectroscopic characterization of [PPh(4)](2)[(bdt)W(O)(S(2))Cu(SC(6)H(4)S(•))] (3; bdt = benzenedithiolate) relevant to the active site of carbon monoxide dehydrogenase are presented. Curiously, in 3, the copper(I) benzenemonothiolate subcenter possesses a dangling thiyl radical that is stabilized by a disulfido-bridged oxo tungsten dithiolene core. The benzenedithiolate ligand, which is generally bidentate in nature, acts as a bidentate and also as a monodentate in 3. The formation of an unusual dangling thiyl radical has been magnetically and spectroscopically identified and has been supported by the density functional theory level of calculation.


Asunto(s)
Cobre/química , Compuestos Organometálicos/química , Tungsteno/química , Cristalografía por Rayos X , Radicales Libres/química , Modelos Moleculares , Conformación Molecular , Compuestos Organometálicos/síntesis química , Oxidación-Reducción
18.
J Am Chem Soc ; 133(13): 4955-64, 2011 Apr 06.
Artículo en Inglés | MEDLINE | ID: mdl-21391675

RESUMEN

Oxalic acid, oxamide, glycolic acid, and glycolamide were employed as 2-carbon linkers to synthesize a series of one-dimensional V(III) polymers from trismesityl vanadium(III)·THF containing a high concentration of low-valent metal sites that can be exploited for Kubas binding in hydrogen storage. Synthesized materials were characterized by powder X-ray diffraction (PXRD), nitrogen adsorption (BET), X-ray photoelectron spectroscopy (XPS), infrared spectroscopy (IR), Raman spectroscopy, thermogravimetric analysis, and elemental analysis. Because each of these organic linkers possesses a different number of protons and coordinating atoms, the products in each case were expected to have different stoichiometries with respect to the number of mesityl groups eliminated and also a different geometry about the V(III) centers. For example, the oxalate and glycolate polymers contained residual mesityl groups; however, these could be exchanged with hydride via hydrogenolysis. The highest adsorption capacity was recorded on the product of trismesityl vanadium(III)·THF with oxamide (3.49 wt % at 77 K and 85 bar). As suggested by the high enthalpy of adsorption (17.9 kJ/mol H(2)), a substantial degree of performance of the vanadium metal centers was retained at room temperature (25%), corresponding to a gravimetric adsorption of 0.87 wt % at 85 bar, close to the performance of MOF-177 at this temperature and pressure. This is remarkable given the BET surface area of this material is only 9 m(2)/g. A calculation on the basis of thermogravimetric results provides 0.88 hydrogen molecule per vanadium center under these conditions. Raman studies with H(2) and D(2) showed the first unequivocal evidence for Kubas binding on a framework metal in an extended solid, and IR studies demonstrated H(D) exchange of the vanadium hydride with coordinated D(2). These spectroscopic observations are sufficient to assign the rising trends in isosteric heats of hydrogen adsorption observed previously by our group in several classes of materials containing low-valent transition metals to the Kubas interaction.


Asunto(s)
Suministros de Energía Eléctrica , Hidrógeno/química , Compuestos Organometálicos/química , Polímeros/química , Vanadio/química , Deuterio/química , Ligandos , Ensayo de Materiales , Estructura Molecular , Compuestos Organometálicos/síntesis química
19.
Anal Chem ; 83(1): 284-8, 2011 Jan 01.
Artículo en Inglés | MEDLINE | ID: mdl-21138285

RESUMEN

Localized surface plasmon resonances in silver and gold nanostructures are engaged to enhance the inelastic Raman scattering and the fluorescence of a phopholipid containing a sulforhodamine 101 acid chloride dye known as Texas Red. The most efficient coupling and enhancement are attained when the excitation laser line is in resonance with both the chromophore and the plasmon absorption of the nanostructure, the case of surface-enhanced resonance Raman scattering, allowing single-molecule detection. The tagged phospholipid was incorporated into a single fatty acid Langmuir monolayer at varying concentrations and transferred onto an evaporated Ag nanoparticle film. Surface-enhanced fluorescence is achieved using shell-isolated silica-coated gold nanoparticles, an emission enhancement named SHINEF.

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