Search results for "Cage"

Three New Medicagenic Acid Saponins from Polygala micranthaGuill. & Perr.

2011

Three new medicagenic acid saponins, micranthosides A–C (1–3), were isolated from the roots of Polygala micranthaGuill. & Perr., along with six known presenegenin saponins. Their structures were elucidated on the basis of extensive 1D- and 2D-NMR experiments (1H, 13C, DEPT, COSY, TOCSY, NOESY, HSQC, and HMBC) and mass spectrometry as 3-O-β-D-glucopyranosylmedicagenic acid 28-[O-β-D-galactopyranosyl-(14)-O-β-D-xylopyranosyl-(14)-O-α-L-rhamnopyranosyl-(12)-β-D-fucopyranosyl] ester (1), 3-O-β-D-glucopyranosylmedicagenic acid 28-[O-6-O-acetyl-β-D-galactopyranosyl-(14)-O-β-D-xylopyranosyl-(14)-O-α-L-rhamnopyranosyl-(12)-β-D-fucopyranosyl] ester (2), and 3-O-{O-β-D-glucopyranosyl-(13)-O-[β-D-gluc…

Binding Profiles of Self-Assembled Supramolecular Cages from ESI-MS Based Methodology

2018

Confined molecular environments have peculiar characteristics that make their properties unique in the field of biological and chemical sciences. In recent years, advances in supramolecular capsule and cage synthesis have presented the possibility to interpret the principles behind their self‐assembly and functions, which has led to new molecular systems that display outstanding properties in molecular recognition and catalysis. Herein, we report a rapid method based on ESI‐MS to determine the binding profiles for linear saturated dicarboxylic acids in a series of different cages. The cages were obtained by self‐assembly of modified tris(pyridylmethyl)amine (TPMA) complexes and diamines cho…

Cyclotriveratrylene-Containing Porphyrins

2016

International audience; The C-3-symmetric cyclotriveratrylene (CTV) was covalently bonded via click chemistry to 1, 2, 3, and 6 zinc(II) porphyrin units to various host for C-60. The binding constants, Ka, were measured from the quenching of the porphyrin fluorescence by C-60. These constants vary between 400 and 4000 M-1 and are considered weak. Computer modeling demonstrated that the zinc(II) porphyrin units, [Zn], exhibit a strong tendency to occupy the CTV cavity, hence blocking the access for C-60 to land on this site. Instead, the pincer of the type [Zn]-[Zn] and in one case [Zn]-CTV, were found to be the most probable geometry to promote host-guest associations in these systems.

Self-assembly of an iron(ii)-based M5L6 metallosupramolecular cage

2011

A pentanuclear M(5)L(6) coordination cage is self-assembled in solution from a rigid linear heteroditopic phen-tpy ligand and an iron (II) salt.

An Unlockable-Relockable Iron Cage by Subcomponent Self-Assembly

2008

Spin state switching in iron coordination compounds

2013

The article deals with coordination compounds of iron(II) that may exhibit thermally induced spin transition, known as spin crossover, depending on the nature of the coordinating ligand sphere. Spin transition in such compounds also occurs under pressure and irradiation with light. The spin states involved have different magnetic and optical properties suitable for their detection and characterization. Spin crossover compounds, though known for more than eight decades, have become most attractive in recent years and are extensively studied by chemists and physicists. The switching properties make such materials potential candidates for practical applications in thermal and pressure sensors …

Inside Cover: A Self-Assembled M8L6 Cubic Cage that Selectively Encapsulates Large Aromatic Guests (Angew. Chem. Int. Ed. 15/2011)

2011

White Phosphorus Is Air-Stable Within a Self-Assembled Tetrahedral Capsule

2009

Molecular Fire Quencher Cage-shaped molecular assemblies can regulate the reactivity of smaller molecules trapped within them. Mal et al. (p. 1697 ) extend this approach to enable the protection of elemental white phosphorus (P 4 ), a substance that rapidly ignites on contact with oxygen. The tetrahedral cages self-assemble in aqueous solution through coordination of six ligands to four iron ions, and efficiently capture phosphorus from a suspension. The water-soluble host-guest constructs were stable in air for at least 4 months, but released intact P 4 rapidly on displacement by added benzene.

Proximity Effect using a Nanocage Structure: Polyhedral Oligomeric Silsesquioxane-Imidazolium Tetrachloro- palladate Salt as a Precatalyst for the Su…

2016

A polyhedral oligomeric silsesquioxane-imidazolium tetrachloropalladate salt (POSS-Imi-PdCl4) was prepared by the reaction of a polyhedral oligomeric silsesquioxane-imidazolium chloride salt (POSS-Imi-Cl) with PdCl2 and used as a pre-catalyst for the Suzuki-Miyaura reaction in water at 100 °C at a low loading (0.08-0.16 mol %). Biphenyl compounds were isolated in high to excellent yields. A comparison of the POSS-based catalyst with the corresponding catalyst without the nanocage structure (i.e., 1-butyl-3-methylimidazolium tetrachloropalladate) highlighted the role of the POSS structure to reach higher yields in the Suzuki-Miyaura reaction. This result is ascribed to a proximity effect of …

Quantitative Rotor Broken Bar Evaluation in Double Squirrel Cage Induction Machines under Dynamic Operating Conditions

2013

Advanced monitoring techniques leading to fault diagnosis and prediction of induction machine faults, operating under non-stationary conditions have gained strength because of its considerable influence on the operational continuation of many industrial processes. In case of rotor broken bars, fault detection based on sideband components issued from currents, flux, instantaneous control or power signals under different load conditions, may fail due to the presence of inter-bar currents that reduce the degree of rotor asymmetry, especially for double squirrel cage induction motors. But the produced core vibrations in the axial direction, can be investigated to overcome the limitation of the …