A Star of David catenane Leigh, David A; Pritchard, Robin G; Stephens, Alexander J
Nature chemistry,
11/2014, Letnik:
6, Številka:
11
Journal Article
Recenzirano
We describe the synthesis of a 2catenane that consists of two triply entwined 114-membered rings, a molecular link. The woven scaffold is a hexameric circular helicate generated by the assembly of ...six tris(bipyridine) ligands with six iron(II) cations, with the size of the helicate promoted by the use of sulfate counterions. The structure of the ligand extension directs subsequent covalent capture of the catenane by ring-closing olefin metathesis. Confirmation of the Star of David topology (two rings, six crossings) is provided by NMR spectroscopy, mass spectrometry and X-ray crystallography. Extraction of the iron(II) ions with tetrasodium ethylenediaminetetraacetate affords the wholly organic molecular link. The self-assembly of interwoven circular frameworks of controlled size, and their subsequent closure by multiple directed covalent bond-forming reactions, provides a powerful strategy for the synthesis of molecular topologies of ever-increasing complexity.
Let's twist again: The one‐pot synthesis of a molecular Solomon link assembles four iron(II) cations, four bis(aldehyde) molecules, and four bis(amine) building blocks. The process generates two ...interwoven 68‐membered‐ring macrocycles, which feature four crossing points, in 75 % yield.
The tetravalency of carbon and its ability to form covalent bonds with itself and other elements enables large organic molecules with complex structures, functions and dynamics to be constructed. The ...varied electronic configurations and bonding patterns of inorganic elements, on the other hand, can impart diverse electronic, magnetic, catalytic and other useful properties to molecular-level structures. Some hybrid organic-inorganic materials that combine features of both chemistries have been developed, most notably metal-organic frameworks, dense and extended organic-inorganic frameworks and coordination polymers. Metal ions have also been incorporated into molecules that contain interlocked subunits, such as rotaxanes and catenanes, and structures in which many inorganic clusters encircle polymer chains have been described. Here we report the synthesis of a series of discrete rotaxane molecules in which inorganic and organic structural units are linked together mechanically at the molecular level. Structural units (dialkyammonium groups) in dumb-bell-shaped organic molecules template the assembly of essentially inorganic 'rings' about 'axles' to form rotaxanes consisting of various numbers of rings and axles. One of the rotaxanes behaves as a 'molecular shuttle': the ring moves between two binding sites on the axle in a large-amplitude motion typical of some synthetic molecular machine systems. The architecture of the rotaxanes ensures that the electronic, magnetic and paramagnetic characteristics of the inorganic rings-properties that could make them suitable as qubits for quantum computers-can influence, and potentially be influenced by, the organic portion of the molecule.
The term “frustration” in the context of magnetism was originally used by P. W. Anderson and quickly adopted for application to the description of spin glasses and later to very special lattice ...types, such as the kagomé. The original use of the term was to describe systems with competing antiferromagnetic interactions and is important in current condensed matter physics in areas such as the description of emergent magnetic monopoles in spin ice. Within molecular magnetism, at least two very different definitions of frustration are used. Here we report the synthesis and characterization of unusual nine-metal rings, using magnetic measurements and inelastic neutron scattering, supported by density functional theory calculations. These compounds show different electronic/magnetic structures caused by frustration, and the findings lead us to propose a classification for frustration within molecular magnets that encompasses and clarifies all previous definitions.
A family of heterometallic CatTixMO(x+1)(O2CtBu)2x+2 rings is reported where Cat=a secondary or tertiary alkyl ammonium ion, x=7, 8 or 9, and M=FeIII, GaIII, CrIII, InIII and AlIII. The structures ...are regular polygons with eight, nine or ten vertices with each edge bridged by an oxide and two pivalates. The size of the ring formed is controlled by the alkylammonium cation present. In each case a homometallic by‐product is found CatTixO(x+1)(O2CtBu)2x−1.
Size control: A family of heterometallic CatTixMO(x+1)(O2C tBu)2x+2 rings is reported where Cat=a secondary or tertiary alkyl ammonium ion, x=7, 8 or 9, and M=Fe, Ga, Cr, In and Al. The structures are regular polygons with eight, nine or ten vertices with each edge bridged by an oxide and two pivalates. The size of the ring formed is controlled by the alkylammonium cation present.
Synthesis of a series of novel N-acylhydrazones of nicotinic acid hydrazides 3a-j via condensation of nicotinic acid hydrazide 1 with the corresponding aldehydes and ketones is described. The series ...3a-j was evaluated for in vitro antibacterial activity against two gram negative (Pseudomonas aeruginosa and Klebsiella pneumoniae) and two gram positive (Streptococcus pneumoniae and Staphylococcus aureus) bacteria. The zone of inhibition was measured using the disk diffusion method, and in vitro minimum inhibitory concentration indicating that compounds 3a and 3e were effective against P. aeruginosa with MICs of 0.220 and 0.195 μg respectively.
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•The formation of perfluoropropenyl transition metal complexes from HFC-1225ye.•The first structurally characterized examples of early TM and bis-substituted perfluoropropenyl ...organometallic complexes.•An assessment of the electronic steric properties of the perfluoropropenyl ligand based on X-ray diffraction data.
The new stable perfluoropropenyl organometallic complexes (Ph3P)Au(E-CF=CFCF3), trans-(Ph3P)2Pt(Z-CF=CFCF3)Cl, trans-(Ph3P)2Pd(E-CF=CFCF3)Cl, (COD)Pt(E-CF=CFCF3)2 and Cp2Ti(E-CF=CFCF3)Cl have been obtained from the reaction of LiCF=CFCF3–derived from Z-CFH=CFCF3 (HFC-1225ye) – with appropriate transition-metal starting materials. The complexes have been characterized by multinuclear NMR studies (19F,1H, 31P and 13C) and single-crystal structure determinations. Based on the X-ray derived data a comparison is made between σ-bound perfluoropropenyl and perfluorovinyl ligands; whilst they are found to be electronically quite similar on the basis of their trans-influence the perfluoropropenyl group is significantly more sterically-demanding, and it is suggested that this accounts for the predominance of mono-perfluoropropenyl-substituted complexes with enhanced stabilities.
Ring around the amine: Reactions which give heterometallic CrxCuy rings can be controlled through choice of reaction times, and the mixed products can be separated and crystallized. These new ...compounds include Cr7Cu, Cr8Cu2, Cr12Cu2, and Cr11Cu2 rings (see structure; Cu orange, Cr green, F yellow, O red, N blue, C black). The last compound is the largest ring known with an odd number of metal atoms.
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