RESUMEN
M8L12 cubic cages (M = Mn(II), Zn(II) or Cd(II)), with all eight metal ions having all facial Δ or facial Λ configurations and having an encapsulated anion, were prepared by the self-assembly of m-xylene-bridged imidazolyl-imine ligands and MX2 (X = PF6(-), SbF6(-), TfO(-)) salts; the encapsulated anion exchange with different anions (SbF6(-), Tf2N(-), NO3(-), TsO(-)) was studied and the results with NO3(-) and TsO(-) indicate that anions on the cage surfaces affect the encapsulated anion exchange and the occupancy of the cage.
RESUMEN
The pyridine-containing ligands and react with Ni(2+) ions to afford dinuclear triple-stranded helicate and tetrahedral cage supramolecular complexes, respectively; the two architectures exhibit contrasting reactivity towards electro- and photocatalytic proton reduction.
RESUMEN
A novel nanohybrid ratiometric fluorescence sensor is developed for selective detection of mercuric ions (Hg(2+)), and the application has been successfully demonstrated in HEPES buffer solution, lake water, and living cells. The sensor comprises water-soluble fluorescent carbon nanoparticles (CNPs) and Rhodamine B (RhB) and exhibits their corresponding dual emissions peaked at 437 and 575 nm, respectively, under a single excitation wavelength (350 nm). The photoluminescence of the CNPs in the nanohybrid system can be completely quenched by Hg(2+) through effective electron or energy transfer process due to synergetic strong electrostatic interaction and metal-ligand coordination between the surface functional group of CNPs and Hg(2+), while that of the RhB remains constant. This results in an obviously distinguishable fluorescence color variation (from violet to orange) of the nanohybrid solution. This novel sensor can effectively identify Hg(2+) from other metal ions with relatively low background interference even in a complex system such as lake water. The detection limit of this method is as low as 42 nM. Furthermore, the sensing technique is applicable to detect Hg(2+) in living cells.
Asunto(s)
Iones/aislamiento & purificación , Mercurio/aislamiento & purificación , Contaminantes Químicos del Agua/aislamiento & purificación , Agua/química , Carbono/química , Iones/química , Límite de Detección , Mercurio/química , Nanopartículas/química , Puntos Cuánticos , Rodaminas/química , Contaminantes Químicos del Agua/químicaRESUMEN
ZnS:Ag2S porous nanostructures are prepared by a simple ion-exchange route using ZnS nanosheets as sacrificial templates. In solutions of different Ag ion concentrations, ZnS nanosheets are partially converted to Ag2S, resulting in porous ZnS:Ag2S nanosheet composites with different pore sizes. With the Ag2S nanocrystals playing the role of hole scavengers, the porous nanosheets exhibit a high photocatalytic H2 generation rate of 104.9 µmol/h/g without using any noble metal cocatalyst.
RESUMEN
Dodecanuclear hexagonal-prismatic M12L18 cages were prepared by a subcomponent self-assembly process with commercially available pyridinecarboxaldehyde, m-xylenediamine, and cadmium(II) perchlorate or manganese(II) perchlorate. The NMR spectrum of the Cd cage shows that there are three independent ligand sets, and the X-ray crystal structure of the Mn cage reveals that the structure has both fac-Δ- and mer-Λ-configured metal centers in a 1:1 ratio. The cage structure also has a large cavity that contains five perchlorate anions.
Asunto(s)
Cadmio/química , Manganeso/química , Compuestos Organometálicos/síntesis química , Piridinas/química , Xilenos/química , Cristalografía por Rayos X , Modelos Moleculares , Estructura Molecular , Compuestos Organometálicos/químicaRESUMEN
Self assembly of phenyl bridged bisbipyridines with manganese perchlorate gave structurally different metallo-macrocycles having cis-labile coordination sites which can catalyse olefin epoxidation with peracetic acid in good yield.
RESUMEN
Highly ordered arrays of Cu-rich and -deficient CuInSe(2) nanotubes as well as ZnO/CuInSe(2) core/sheath nanocables have been synthesized on glass substrates by using ZnO nanorod arrays as sacrificial templates via a low-cost solution method. Chemical conversions from hexagonal ZnO to cubic ZnSe, hexagonal CuSe and tetragonal CuInSe(2) are demonstrated as a novel means for synthesis of I-III-VI nanomaterials. Large differences in their solubility product constant (K(sp)) are crucial for direct exchange in the conversions. In solvothermal reaction of ZnO/CuSe core/shell nanocables with InCl(3), the triethylene glycol solvent serves as a reducing agent for the reduction of cupric (Cu(2+)) to cuprous (Cu(+)) ions and also as an agent for the dissolution of ZnO cores. The absorption coefficient of the CuInSe(2) nanotubes in the visible region is on the order of 10(4) cm(-1). Photoelectrochemical solar cells were fabricated with arrays of ZnO/Cu(1.57±0.10)In(0.68±0.10)Se(2) and ZnO/CuSe nanocables. It was found that power conversion efficiency of the ZnO/Cu(1.57±0.10)In(0.68±0.10)Se(2) cell is about two times higher than that based on ZnO/CuSe.
RESUMEN
New binuclear double-stranded helicates were formed between manganese(ii) perchlorate and chiral phenyl- and polyphenyl-bridged oligopyridines; they are active catalysts for alkene epoxidation.
Asunto(s)
Alquenos/química , Compuestos Epoxi/química , Manganeso/química , Catálisis , Dicroismo Circular , Cristalografía por Rayos X , Conformación Molecular , Percloratos/química , Piridinas/química , Espectrometría de Masa por Ionización de Electrospray , EstereoisomerismoRESUMEN
Reaction of a pinene-based pyridylthioamide with 1,4-dibromo-2,3-butanedione in refluxing methanol yielded a new chiral pyridylthiazole ligand L which forms a dinuclear double-stranded helicate with Cu(i) ions; this helicate has opposite helical chirality when compared with its quaterpyridine analogue.
Asunto(s)
Cobre/química , Tiazoles/síntesis química , Butanonas/síntesis química , Cationes Bivalentes/química , Ligandos , Estereoisomerismo , Tiazoles/químicaRESUMEN
A series of single-stranded helical Re(I) complexes, of formula [Re(2)(L)Br(2)(CO)(6)], were prepared by reacting [Re(CO)(5)Br] with chiral quaterpyridines L1-4. By (1)H and (13)C NMR analysis, all the crude complexes consisted of a pair of stereoisomers. Sterically more demanding ligand L4 induced a higher ratio (80:20) than L1-3 (about 56:44). Stereochemically pure complexes could be obtained by recrystallization in CH(2)Cl(2). X-ray crystallographic analysis of single crystals from purified complexes showed a single-stranded helical structure with a bridging ligand wrapped around two distorted octahedral rhenium metals, both of which possessed one bromide ligand and three carbonyl ligands in a fac coordination. The helical core is established by extensive noncovalent electrostatic interactions and chiral information is transmitted from the ligand to the helix through these interactions. Solution behavior was studied by CD spectroscopy, and the strong Cotton effect confirms the integrity of the helical structure in solution. The diastereoselectivity of helicates is proposed to be induced by steric interaction between the bromine atom and the substituent of the bridging ligand.
Asunto(s)
Cristalografía por Rayos X , Piridinas/química , Renio/química , Bromuros/síntesis química , Bromuros/química , Enlace de Hidrógeno , Ligandos , Espectroscopía de Resonancia Magnética , Modelos Moleculares , Estructura Molecular , Piridinas/síntesis química , Teoría Cuántica , EstereoisomerismoRESUMEN
A chiral iron-sexipyridine complex-hydrogen peroxide mixture is a highly efficient catalytic system for styrene epoxidation with excellent reactivity (3 min, 95% yield) and chemoselectivity (98%).
Asunto(s)
Alquenos/química , Compuestos Epoxi/síntesis química , Peróxido de Hidrógeno/química , Hierro/química , Piridinas/química , Catálisis , Dicroismo Circular , Ligandos , Níquel/química , Paladio/química , EstereoisomerismoRESUMEN
Chiral double-stranded helicates, formed between Cu(I) ion and C(2)-symmetric oligopyridines, were used for catalytic asymmetric cyclopropanation of alkenes; low catalyst loadings (0.2 mol%), high TONs (up to 404) and short reaction times (30-60 min) were achieved with [Cu(2)L(2)]OTf(2)(L = chiral C(2)-symmetric terpyridine).
Asunto(s)
Cobre/química , Ciclopropanos/química , Compuestos Organometálicos/síntesis química , Piridinas/química , Cristalografía por Rayos X , Ligandos , Sustancias Macromoleculares/síntesis química , Sustancias Macromoleculares/química , Conformación Molecular , Compuestos Organometálicos/química , EstereoisomerismoRESUMEN
Re(I) tricarbonyl bipyridine and terpyridine complexes catalyse stereospecific cyclopropanation of alkenes; high selectivity of cyclopropane vs coupling and an ee of 73% and 62% for cis- and trans-cyclopropanes of styrene respectively were achieved with the [Re(L)(CO)(3)(MeCN)]OTf complex (L = chiral C(2)-symmetric terpyridine ligand).
Asunto(s)
Alquenos/química , Ciclopropanos/química , Cetonas/química , Piridinas/química , Renio/química , Catálisis , Espectroscopía de Resonancia Magnética , Modelos Moleculares , Espectrometría de Masa por Ionización de ElectrosprayRESUMEN
Chiral C2-symmetric quaterpyridine L reacts with [Pd(eta3-C3H5)Cl]2 to form a chiral single-stranded helical binuclear palladium complex of formula [Pd2(eta3-C3H5)2(L)]2+; the complex can efficiently catalyze allylic substitution of 1,3-diphenylprop-2-enyl acetate with dimethyl malonate with enantioselectivity up to 85%.
RESUMEN
The first series of chiral 2,2':6',2''-terpyridine tri-N-oxide ligands have been developed; They were showed to be active Lewis base-catalysts for asymmetric allylation of aldehydes using allyltrichlorosilane with optimal results at 0 degrees C for electron-deficient aromatic aldehydes (yields up to 97% and enantioselectivities up to 86% ee).
RESUMEN
Terpyridine macrocycle 1 is shown to be a strong chelating agent for organic ammonium salts and also a useful chromophore in fluorescent sensing. It exhibits very good enantioselectivity (K(obs)(S)/K(obs)(R)= 3.8) in chiral discrimination of alpha-phenylglycine methyl ester hydrochloride (PhEtOMe).