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Fraser J Stoddart - One of the best experts on this subject based on the ideXlab platform.
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topological isomerism in a chiral handcuff catenane
Chemical Science, 2014Co-Authors: Karel J Hartlieb, Ross S Forgan, Anthea K Blackburn, Severin T Schneebeli, Amy A Sarjeant, Charlotte L Stern, Fraser J StoddartAbstract:The self-assembly of two topological isomers of a handcuff catenane has been achieved by utilizing the Template-Directed Synthesis between the π-electron-rich bis-1,5-dioxynaphtho[50]crown-14 and the precursors to two fused π-electron-deficient cyclobis(paraquat-p-phenylene) cyclophanes. Characterization of the product using 1H NMR spectroscopy and single-crystal X-ray diffraction, with supporting density functional theory (DFT) calculations, suggests that the 1,5-dioxynaphthalene units in the major topological isomer align themselves with the same relative orientations inside the cyclophanes on account of restrictions imposed by the lengths of the polyether loops. The DFT calculations also reveal that the energies of the two topological isomers are similar to each other, supporting the experimental observation that both isomers can be isolated as a mixture from a one-pot reaction. The two isomers – designated as the meta–meta and ortho–ortho isomers with different topologies that are not interconvertible – only differ in the manner in which the polyether loops wind their way around the central 1,2,4,5-tetrasubstituted benzenoid ring in the ditopic host. X-Ray crystallography proves that by far the major topological isomer in the solid state is the meta–meta one. 1H NMR spectroscopy confirms that it is also the major isomer in solution, whilst also revealing the presence of a minor isomer, which is assumed, for the time-being, to have the ortho–ortho topology. The free fused ditopic host has been obtained using a protocol similar to that employed in the Template-Directed Synthesis of the handcuff catenane, except that the crown ether is replaced with an acyclic template which can be removed post-Synthesis. The results of isothermal titration calorimetry studies shed some light on the mechanism of binding of π-electron-rich guests: they lead us to believe that when two electron-rich guests bind to the ditopic host, they do so with allosteric negative cooperativity.
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positive cooperativity in the template directed Synthesis of monodisperse macromolecules
Journal of the American Chemical Society, 2012Co-Authors: Matthew E Belowich, Cory Valente, Ronald A Smaldone, Douglas C Friedman, Johannes Thiel, Leroy Cronin, Fraser J StoddartAbstract:Two series of oligorotaxanes R and R′ that contain −CH2NH2+CH2– recognition sites in their dumbbell components have been synthesized employing Template-Directed protocols. [24]Crown-8 rings self-assemble by a clipping strategy around each and every recognition site using equimolar amounts of 2,6-pyridinedicarboxaldehyde and tetraethyleneglycol bis(2-aminophenyl) ether to efficiently provide up to a [20]rotaxane. In the R series, the −NH2+– recognition sites are separated by trismethylene bridges, whereas in the R′ series the spacers are p-phenylene linkers. The underpinning idea here is that in the former series, the recognition sites are strategically positioned 3.5 A apart from one another so as to facilitate efficient [π···π] stacking between the aromatic residues in contiguous rings in the rotaxanes and consequently, a discrete rigid and rod-like conformation is realized; these noncovalent interactions are absent in the latter series rendering them conformationally flexible/nondiscrete. Although in th...
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monofunctionalized pillar 5 arene as a host for alkanediamines
Journal of the American Chemical Society, 2011Co-Authors: Nathan L. Strutt, Ross S Forgan, Jason M Spruell, Youssry Y Botros, Fraser J StoddartAbstract:Alkanediamines serve as neutral guests for the recently discovered host pillar[5]arene. The proposed [2]pseudorotaxane nature of the superstructure of the 1:1 host-guest complexes is supported by the Template-Directed Synthesis of a related [2]rotaxane. A synthetic route to monofunctional pillar[5]arenes has also been developed, allowing for the creation of a fluorescent sensor for alkylamine binding. The precursors to this host could act as starting points for a large library of monofunctional pillar[5]arene macrocycles.
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isolation by crystallization of translational isomers of a bistable donor acceptor 2 catenane
Proceedings of the National Academy of Sciences of the United States of America, 2010Co-Authors: Cheng Wang, Mark A Olson, Lei Fang, Diego Benitez, Ekaterina Tkatchouk, Subhadeep Basu, Ashish N Basuray, Deqing Zhang, William A Goddard, Fraser J StoddartAbstract:The Template-Directed Synthesis of a bistable donor-acceptor [2]catenane wherein both translational isomers—one in which a tetrathiafulvalene unit in a mechanically interlocked crown ether occupies the cavity of a cyclobis(paraquat-p-phenylene) ring and the other in which a 1,5-dioxynaphthalene unit in the crown ether resides inside the cavity of the tetracationic cyclophane—exist in equilibrium in solution, has led to the isolation and separation by hand picking of single crystals colored red and green, respectively. These two crystalline co-conformations have been characterized separately at both the molecular and supramolecular levels, and also by dynamic NMR spectroscopy in solution where there is compelling evidence that the mechanically interlocked molecules are present as a complex mixture of translational, configurational, and conformational isomers wherein the isomerization is best described as being a highly dynamic and adaptable phenomenon.
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template directed Synthesis of donor acceptor 2 catenanes and 2 rotaxanes
Pure and Applied Chemistry, 2008Co-Authors: Kirsten E Griffiths, Fraser J StoddartAbstract:The Synthesis of mechanically interlocked molecular compounds has advanced by leaps and bounds since the early days of statistical methods and covalent-directing strategies. Template-Directed Synthesis has emerged as the method of choice for the construction of increasingly complex and functional [2]catenanes and [2]rotaxanes. In particular, mechanically interlocked molecules employing π-donating and π-accepting recognition units have been produced with remarkable efficiencies and show great promise in technologies as diverse as molecular electronics and drug delivery.
Genqiang Zhang - One of the best experts on this subject based on the ideXlab platform.
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dual functional template directed Synthesis of mose2 carbon hybrid nanotubes with highly disordered layer structures as efficient alkali ion storage anodes beyond lithium
ACS Applied Materials & Interfaces, 2020Co-Authors: Yi Liu, Liang Shi, Shuhong Jiao, Suyuan Zeng, Genqiang ZhangAbstract:Sodium/Potassium-ion batteries (SIBs/PIBs) have recently received tremendous attention because of their particular features of cost-effectiveness and promising energy density, which hold great potential for large-scale applications. Nevertheless, it still has a common bottleneck issue that is the sluggish kinetics of Na+/K+ intercalation, which raises more rigorous requirement on the electrode candidates regarding the morphology, dimension, and architecture. Herein, we have constructed unique MoSe2-based hybrid nanotubes with wall structures composed of highly disordered MoSe2 layers embedded in phosphorus and nitrogen co-doped carbon matrix (denoted MoSe2⊂PNC-HNTs), by a facile two-step strategy using Se nanorods as the dual-functional template, i.e., shape-directed agent and in situ selenization resources. Benefitting from the combined features of the one-dimensional (1D) hollow interior, hybrid wall structure with high disorder, and the phosphorus and nitrogen co-doping-induced abundant defect sites in the carbon matrix, the MoSe2⊂PNC-HNT anode exhibits high specific capacities of 280 and 262 mA h g-1 over 200 cycles at the current density of 0.1 A g-1 for Na+ and K+ storage, respectively, and achieves remarkable capacity retention rates of 87.0% at 2 A g-1 over 3500 cycles for Na-ion storage and 80.1% at 1 A g-1 after 500 cycles for K-ion storage.
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dual functional template directed Synthesis of mose2 carbon hybrid nanotubes with highly disordered layer structures as efficient alkali ion storage anodes beyond lithium
ACS Applied Materials & Interfaces, 2020Co-Authors: Yi Liu, Liang Shi, Shuhong Jiao, Suyuan Zeng, Genqiang ZhangAbstract:Sodium/Potassium-ion batteries (SIBs/PIBs) have recently received tremendous attention because of their particular features of cost-effectiveness and promising energy density, which hold great pote...
Harry L. Anderson - One of the best experts on this subject based on the ideXlab platform.
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global aromaticity in a partially fused 8 porphyrin nanoring
Journal of the American Chemical Society, 2020Co-Authors: Sebastian M Kopp, Henrik Gotfredsen, Timothy D. W. Claridge, Jieren Deng, Harry L. AndersonAbstract:Template-Directed Synthesis has been used to prepare a fully π-conjugated cyclic porphyrin octamer, composed of both β,meso,β-edge-fused porphyrin tape units and butadiyne-linked porphyrins. The UV-vis-NIR spectra of this partially fused nanoring show that π-conjugation extends around the whole macrocycle, and that it has a smaller HOMO-LUMO gap than its all-butadiyne-linked analogue, as predicted by TD-DFT calculations. The 1H NMR shifts of the bound templates confirm the disrupted aromaticity of the edge-fused porphyrins in the neutral nanoring. NMR oxidation titrations reveal the presence of a global paratropic ring current in its 4+ and 8+ oxidation states and of a global diatropic ring current in the 6+ state of the partially fused ring. The paratropic ring current in the 4+ oxidation state is about four times stronger than that in the all-butadiyne-linked cyclic octamer complex, whereas the diatropic current in the 6+ state is about 40% weaker. Two isomeric K-shaped tetrapyridyl templates with trifluoromethyl substituents at different positions were used to probe the distribution of the ring current in the 4+, 6+, and 8+ oxidation states by 19F NMR, demonstrating that the ring currents are global and homogeneous.
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allosteric cooperativity and template directed Synthesis with stacked ligands in porphyrin nanorings
Journal of the American Chemical Society, 2020Co-Authors: Pernille S Bols, Michel Rickhaus, Michael Jirásek, Lara Tejerina, Henrik Gotfredsen, Kristina Eriksen, Harry L. AndersonAbstract:The link between allosteric cooperativity and Template-Directed Synthesis has been investigated by studying complexes in which two oligopyridine ligands bind inside a zinc porphyrin nanoring in a s...
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Tuning the Circumference of Six-Porphyrin Nanorings
2019Co-Authors: Renée Haver, Michel Rickhaus, Michael Jirásek, Lara Tejerina, Hua-wei Jiang, Laura M. Herz, Isabell Grübner, Hannah J. Eggimann, Harry L. AndersonAbstract:Most macrocycles are made from a simple repeat unit, resulting in high symmetry. Breaking this symmetry allows fine-tuning of the circumference, providing better control of the host–guest behavior and electronic structure. Here, we present the Template-Directed Synthesis of two unsymmetrical cyclic porphyrin hexamers with both ethyne (C2) and butadiyne (C4) links, and we compare these nanorings with the symmetrical analogues with six ethyne or six butadiyne links. Inserting two extra carbon atoms into the smaller nanoring causes a spectacular change in binding behavior: the template affinity increases by a factor of 3 × 109, to a value of ca. 1038 M–1, and the mean effective molarity is ca. 830 M. In contrast, removing two carbon atoms from the largest nanoring results in almost no change in its template-affinity. The strain in these nanorings is 90–130 kJ mol–1, as estimated both from DFT calculation of homodesmotic reactions and from comparing template affinities of linear and cyclic oligomers. Breaking the symmetry has little effect on the absorption and fluorescence behavior of the nanorings: the low radiative rates that are characteristic of a circular delocalized S1 excited state are preserved in the low-symmetry macrocycles
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Unexpected Interactions between Alkyl Straps and Pyridine Ligands in Sulfur-Strapped Porphyrin Nanorings
2017Co-Authors: Cécile Roche, Amber L Thompson, Hua-wei Jiang, Qianfu Luo, Guzmán Gil-ramírez, Daniel R. Kohn, Yaoyao Xiong, Harry L. AndersonAbstract:Strapped or “basket-handle” porphyrins have been investigated previously as hemoglobin mimics and catalysts. The facial selectivity of their interactions with axial ligands is a sensitive test for noncovalent bonding. Here the binding of pyridyl ligands to zinc porphyrins with thioester-linked alkyl straps is investigated in solution by NMR spectroscopy and UV–vis titration, and in the solid state by X-ray crystallography. We expected that coordination of the axial ligand would occur on the less hindered face of the porphyrin, away from the strap. Surprisingly, attractive interactions between the strap and the ligand direct axial coordination to the strapped face of the porphyrin, except when the strap is short and tight. The strapped porphyrins were incorporated into π-conjugated cyclic porphyrin hexamers using Template-Directed Synthesis. The strap and the sulfur substituents are located either inside or outside the porphyrin nanoring, depending on the length of the strap. Six-porphyrin nanorings with outwardly pointing sulfur anchors were prepared for exploring quantum interference effects in single-molecule charge transport
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caterpillar track complexes in template directed Synthesis and correlated molecular motion
Angewandte Chemie, 2015Co-Authors: Shiqi Liu, Dmitry V. Kondratuk, Timothy D. W. Claridge, Sophie A L Rousseaux, Guzman Gilramirez, Melanie C Osullivan, Jonathan Cremers, Harry L. AndersonAbstract:Small alterations to the structure of a star-shaped template totally change its mode of operation. The hexapyridyl template directs the conversion of a porphyrin dimer to the cyclic hexamer, but deleting one pyridine site changes the product to the cyclic decamer, while deleting two binding sites changes the product to the cyclic octamer. This surprising switch in selectivity is explained by the formation of 2:1 caterpillar track complexes, in which two template wheels bind inside the nanoring. Caterpillar track complexes can also be prepared by binding the hexapyridyl template inside the 8- and 10-porphyrin nanorings. NMR exchange spectroscopy (EXSY) experiments show that these complexes exhibit correlated motion, in which the conrotatory rotation of the two template wheels is coupled to rotation of the nanoring track. In the case of the 10-porphyrin system, the correlated motion can be locked by binding palladium(II) dichloride between the two templates.
Christopher A Hunter - One of the best experts on this subject based on the ideXlab platform.
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sequence information transfer using covalent template directed Synthesis
Chemical Science, 2019Co-Authors: Diego Nunezvillanueva, Maria Ciaccia, Giulia Iadevaia, Elena Sanna, Christopher A HunterAbstract:Template-Directed Synthesis is the biological method for the assembly of oligomers of defined sequence, providing the molecular basis for replication and the process of evolution. To apply analogous processes to synthetic oligomeric molecules, methods are required for the transfer of sequence information from a template to a daughter strand. We show that covalent Template-Directed Synthesis is a promising approach for the molecular replication of sequence information in synthetic oligomers. Two monomer building blocks were synthesized: a phenol monomer and a benzoic acid monomer, each bearing an alkyne and an azide for oligomerization via copper catalyzed azide alkyne cycloaddition (CuAAC) reactions. Stepwise Synthesis was used to prepare oligomers, where information was encoded as the sequence of phenol (P) and benzoic acid (A) units. Ester base-pairing was used to attach monomers to a mixed sequence template, and CuAAC was used to zip up the backbone. Hydrolysis of the ester base-pairs gave back the starting template and the sequence complementary copy. When the AAP trimer was used as the template, the complementary sequence PPA was obtained as the major product, with a small amount of scrambling resulting in PAP as a side-product. This covalent base-pairing strategy represents a general approach that can be implemented in different formats for the replication of sequence information in synthetic oligomers.
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Synthesis of a molecular trefoil knot by folding and closing on an octahedral coordination template
Nature Chemistry, 2010Co-Authors: Jun Guo, Paul C Mayers, Gloria Anne Breault, Christopher A HunterAbstract:The advent of Template-Directed Synthesis has provided access to a range of new interlocked molecular architectures. Although many syntheses of molecular catenanes and rotaxanes have been reported, molecular knots are a class of molecules with topologically non-planar graphs that are rather rare. Here we report a synthetic strategy for the preparation of a molecular trefoil knot from a flexible bipyridine oligomer and a zinc(II) octahedral coordination template. The oligomer folds into a stable open-knot conformation in the presence of the template, and trapping of this arrangement through esterification or ring-closing metathesis produces the closed-knot complex. Subsequent removal of the template from the metathesis product results in a molecular trefoil knot.
Liang Shi - One of the best experts on this subject based on the ideXlab platform.
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dual functional template directed Synthesis of mose2 carbon hybrid nanotubes with highly disordered layer structures as efficient alkali ion storage anodes beyond lithium
ACS Applied Materials & Interfaces, 2020Co-Authors: Yi Liu, Liang Shi, Shuhong Jiao, Suyuan Zeng, Genqiang ZhangAbstract:Sodium/Potassium-ion batteries (SIBs/PIBs) have recently received tremendous attention because of their particular features of cost-effectiveness and promising energy density, which hold great pote...
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dual functional template directed Synthesis of mose2 carbon hybrid nanotubes with highly disordered layer structures as efficient alkali ion storage anodes beyond lithium
ACS Applied Materials & Interfaces, 2020Co-Authors: Yi Liu, Liang Shi, Shuhong Jiao, Suyuan Zeng, Genqiang ZhangAbstract:Sodium/Potassium-ion batteries (SIBs/PIBs) have recently received tremendous attention because of their particular features of cost-effectiveness and promising energy density, which hold great potential for large-scale applications. Nevertheless, it still has a common bottleneck issue that is the sluggish kinetics of Na+/K+ intercalation, which raises more rigorous requirement on the electrode candidates regarding the morphology, dimension, and architecture. Herein, we have constructed unique MoSe2-based hybrid nanotubes with wall structures composed of highly disordered MoSe2 layers embedded in phosphorus and nitrogen co-doped carbon matrix (denoted MoSe2⊂PNC-HNTs), by a facile two-step strategy using Se nanorods as the dual-functional template, i.e., shape-directed agent and in situ selenization resources. Benefitting from the combined features of the one-dimensional (1D) hollow interior, hybrid wall structure with high disorder, and the phosphorus and nitrogen co-doping-induced abundant defect sites in the carbon matrix, the MoSe2⊂PNC-HNT anode exhibits high specific capacities of 280 and 262 mA h g-1 over 200 cycles at the current density of 0.1 A g-1 for Na+ and K+ storage, respectively, and achieves remarkable capacity retention rates of 87.0% at 2 A g-1 over 3500 cycles for Na-ion storage and 80.1% at 1 A g-1 after 500 cycles for K-ion storage.
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template directed Synthesis of ordered single crystalline nanowires arrays of cu2znsns4 and cu2znsnse4
Journal of the American Chemical Society, 2011Co-Authors: Liang Shi, Congjian PeiAbstract:Highly ordered quaternary semiconductor Cu2ZnSnS4 nanowires array have been prepared via a facile solvothermal approach using anodic aluminum oxide (AAO) as a hard template. The as-prepared nanowires are uniform and single crystalline. They grow along either the crystalline [110] or [111] direction. The structure, morphology, composition, and optical absorption properties of the as-prepared Cu2ZnSnS4 samples were characterized using X-ray powder diffraction, transmission electron microscopy, energy dispersive X-ray spectrometry, scanning electron microscopy, and UV–vis spectrometry. A possible formation mechanism of the nanowire arrays is proposed. Governed by similar mechanism, we show that Cu2ZnSnSe4 nanowire array with similar structural characteristics can also be obtained.
