1,721,099 research outputs found
Tetranuclear Zn2Ln2 coordination clusters as catalysts in the Petasis borono-Mannich multicomponent reaction
No full textWe report herein for the first time the efficiency of heteronuclear Zn/Ln coordination clusters (CCs) as catalysts for the multicomponent Mannich-type condensation that involves amines, aldehydes and boronic acids, known as the Petasis borono-Mannich (RBR) reaction. The reaction proceeds in very good to excellent yields (84–98%, 17 products) at room temperature with catalyst loadings as low as 1.0 mol%
Highly efficient tetranuclear ZnII2LnIII2 catalysts for the Friedel–Crafts alkylation of indoles and nitrostyrenes
No full textWe demonstrate for the first time the high efficacy of tetranuclear ZnII2LnIII2 coordination clusters (CCs) as catalysts for the Friedel–Crafts (FC) alkylation of indoles with a range of trans-?-nitrostyrenes. The reaction proceeds in good to excellent yields (76%–99%) at room temperature with catalyst loadings as low as 1.0 mol
Chemical chartographisis: a contemporary perspective in molecular design and synthesis
No full textThe use of flexible molecular systems in solution, without strictly controlling their behaviour, has frequently been productive. Their potential could increase by a more holistic view of the reaction(s) process(es) in which they are involved. In this perspective, we introduce a broader approach - “Chemical Chartographisis” - and discuss three projects in detail to illustrate its potential. The topics involve bimetallic 3d/4f species and coordination compounds built from benzotriazole-based and (a)symmetric salan ligands and focus on catalytic and, in less detail, biological-related examples.</p
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Single enantiomer propeller-shaped polynuclear complexes as catalysts – proof-of-concept for enantioinduction in a Michael addition reaction
No full textWe report a family of propeller-shaped polynuclear metal complexes whose overall chirality is dictated by a single stereogenic centre within their component amino alcohol- ligand. These topologically intriguing complexes are readily prepared in enantiomerically pure form and are shown here to catalyse the conjugate addition of barbituric acids and their derivatives to nitroalkenes, with a catalyst loading of 1 mol%. Although only low levels of enantioinduction are observed, control experiments indicate that the enantioselectivity is dictated by the overall topology of the complex and not governed by binding to the tetrametallic entity, heralding a potentially new mode of catalysis.</p
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Chemical chartographisis: a contemporary perspective in molecular design and synthesis
No full textThe use of flexible molecular systems in solution, without strictly controlling their behaviour, has frequently been productive. Their potential could increase by a more holistic view of the reaction(s) process(es) in which they are involved. In this perspective, we introduce a broader approach - “Chemical Chartographisis” - and discuss three projects in detail to illustrate its potential. The topics involve bimetallic 3d/4f species and coordination compounds built from benzotriazole-based and (a)symmetric salan ligands and focus on catalytic and, in less detail, biological-related examples.</p
Twists to the spin structure of the Ln9-diabolo motif exemplified in two {Zn2Ln2}[Ln9]{Zn2} coordination clusters
No full textTwo pentadecanuclear Zn4Ln11 [with Ln = Gd(1) or Dy(2)] coordination clusters, best formulated as {Zn2Ln2}[Ln9]{Zn2}, are presented. The central {Ln9} diabolo core has a {Zn2Ln2} handle motif pulling at two outer Ln ions of the central core via two {ZnLn} units, which also invest the system with C2 point symmetry. The resulting cluster motif is supported on two Zn “feet”, corresponding to the {Zn2} unit in the formula. A thorough investigation of the magnetic properties in the light of the properties of previously reported {Ln9} diabolo compounds was undertaken. Up to now, the spin structure of such diabolo motifs usually proves ambiguous. Our magnetic studies show that the orientation of the central spin in the {Gd9} diabolo plays a decisive role. In stabilizing the core by attachment of the {Zn}2+ “feet” and using the C2 symmetry related {ZnGd}5+ handles to influence the spin direction of the central Gd of the {Gd9} diabolo we can understand why the “naked” {Gd9} diabolo shows ambiguous spin structure. This then allowed us to elucidate the single molecule magnetic (SMM) properties of the Dy based compound 2 through disentangling the magnetic properties of the isostructural Gd based compound 1
Recent Bio-Advances in Metal-Organic Frameworks
No full textMetal-organic frameworks (MOFs) have found uses in adsorption, catalysis, gas storage and other industrial applications. Metal Biomolecule Frameworks (bioMOFs) represent an overlap between inorganic, material and medicinal sciences, utilising the porous frameworks for biologically relevant purposes. This review details advances in bioMOFs, looking at the synthesis, properties and applications of both bioinspired materials and MOFs used for bioapplications, such as drug delivery, imaging and catalysis, with a focus on examples from the last five years
Review: Recent advances of one-dimensional coordination polymers as catalysts
No full textThis review aims to provide reports of one dimensional (1-D) coordination polymers that have been used as catalysts in various organic reactions in the last decade, covering the literature from 2007 and onwards. The CPs have been mainly categorized into homometallic and heterometallic compounds; additional parameters such as the metal and ligand selection for the CP are discussed to provide a more detailed look into each system
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Recent advances in the coordination chemistry of benzotriazole-based ligands
No full textWith the use of N-donor ligands in coordination chemistry receiving significant interest and attention in the last few decades, benzotriazole has emerged as an ideal molecule that provides many synthetic advantages and reliable routes towards polynuclear coordination clusters and coordination polymers. In order to fully realise this potential, the current work provides a systematic study of the recent advances on the use of benzotriazole and its derivatives as ligands in coordination chemistry. The reported complexes have been primarily categorized in regards to the exact linker used and its role in the resulting architecture (either as a main or as a secondary ligand). Important structural information, as well as notable properties (such as magnetism, catalysis, luminescence, bio-applications) are also mentioned for the compounds
Tubular glassy carbon microneedles with fullerene-like tips for biomedical applications
No full textGlassy carbon, in general, is made by the pyrolysis of polymeric materials and has been the subject of research for at least fifty years. However, as understanding its microstructure is far from straightforward, it continues to be an area of active research. Glassy carbon adopts different allotropes depending on the hybridizations of the C–C bond, that is, sp, sp2, or sp3. Furthermore, a variety of short-range ordering effects can interact with each other and this, along with the effects of microporosity, grain boundaries, and defects, render this a fascinating material. Following the nanoarchitectonics concept of bottom-up creation of functional materials, we use methane rather than a polymer to form glassy carbon. Here we show that tubular glassy carbon microneedles with fullerenelike tips form when methane undergoes pyrolysis on a curved alumina surface. X-ray diffraction of these glassy carbon tubules shows long-range order with a d-spacing of 4.89 Å, which is indicative of glassy carbon. Raman spectroscopy shows the material to be graphitic in nature, and SEM shows the fullerene-like structure of the material. This work provides new insights into the structure of glassy carbons relevant to the application of glassy carbons as a biomaterial, for example, as a new form of carbon-based microneedles. Since metallic needles can introduce toxic/allergenic species into susceptible subjects, this alternative carbon-based microneedle form has great potential as a replacement biomedical material for metallic needles in the field of neural engineering and as acupuncture needles
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