A Solomon Link through an Interwoven Molecular Grid Beves, Jonathon E.; Danon, Jonathan J.; Leigh, David A. ...
Angewandte Chemie (International ed.),
June 22, 2015, Letnik:
54, Številka:
26
Journal Article
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A molecular Solomon link was synthesized through the assembly of an interwoven molecular grid consisting of four bis(benzimidazolepyridyl)benzthiazolo5,4‐dthiazole ligands and four zinc(II), ...iron(II), or cobalt(II) cations, followed by ring‐closing olefin metathesis. NMR spectroscopy, mass spectrometry, and X‐ray crystallography confirmed the doubly interlocked topology, and subsequent demetalation afforded the wholly organic Solomon link. The synthesis, in which each metal ion defines the crossing point of two ligand strands, suggests that interwoven molecular grids should be useful scaffolds for the rational construction of other topologically complex structures.
Gridlocked: A molecular Solomon link was obtained in 72 % yield through the self‐assembly of a 2×2 interwoven molecular grid consisting of four thiazole ligands and four transition‐metal cations, followed by ring‐closing olefin metathesis. Interwoven grids should prove to be useful intermediates in the synthesis to higher‐order molecular knots and links.
Effects of knot tightness at the molecular level Zhang, Liang; Lemonnier, Jean-François; Acocella, Angela ...
Proceedings of the National Academy of Sciences - PNAS,
02/2019, Letnik:
116, Številka:
7
Journal Article
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Three 819 knots in closed-loop strands of different lengths (∼20, 23, and 26 nm) were used to experimentally assess the consequences of knot tightness at the molecular level. Through the use of ¹H ...NMR, diffusion-ordered spectroscopy (DOSY), circular dichroism (CD), collision-induced dissociation mass spectrometry (CID-MS) and molecular dynamics (MD) simulations on the different-sized knots, we find that the structure, dynamics, and reactivity of the molecular chains are dramatically affected by the tightness of the knotting. The tautness of entanglement causes differences in conformation, enhances the expression of topological chirality, weakens covalent bonds, inhibits decomplexation events, and changes absorption properties. Understanding the effects of tightening nanoscale knots may usefully inform the design of knotted and entangled molecular materials.
We report on a complex featuring three 2,6-pyridinedicarboxamide ligands entwined around a lanthanide (Ln3+) ion. The ligand strands can be cyclized by ring-closing olefin metathesis to form a ...molecular trefoil knot in 58% yield. Demetalation with tetraethylammonium fluoride quantitatively generates the wholly organic 81-atom-loop trefoil knot.
Braiding a molecular knot with eight crossings Danon, Jonathan J.; Krüger, Anneke; Leigh, David A. ...
Science (American Association for the Advancement of Science),
01/2017, Letnik:
355, Številka:
6321
Journal Article
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Knots may ultimately prove just as versatile and useful at the nanoscale as at the macroscale. However, the lack of synthetic routes to all but the simplest molecular knots currently prevents ...systematic investigation of the influence of knotting at the molecular level. We found that it is possible to assemble four building blocks into three braided ligand strands. Octahedral iron(II) ions control the relative positions of the three strands at each crossing point in a circular triple helicate, while structural constraints on the ligands determine the braiding connections. This approach enables two-step assembly of a molecular 819 knot featuring eight nonalternating crossings in a 192-atom closed loop ~20 nanometers in length. The resolved metal-free 819 knot enantiomers have pronounced features in their circular dichroism spectra resulting solely from topological chirality.
Coordination Chemistry of a Molecular Pentafoil Knot Zhang, Liang; Stephens, Alexander J; Lemonnier, Jean-François ...
Journal of the American Chemical Society,
03/2019, Letnik:
141, Številka:
9
Journal Article
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The binding of Zn(II) cations to a pentafoil (51) knotted ligand allows the synthesis of otherwise inaccessible metalated molecular pentafoil knots via transmetalation, affording the corresponding ...“first-sphere” coordination Co(II), Ni(II), and Cu(II) pentanuclear knots in good yields (≥85%). Each of the knot complexes was characterized by mass spectrometry, the diamagnetic (zinc) knot complex was characterized by 1H and 13C NMR spectroscopy, and the zinc, cobalt, and nickel pentafoil knots afforded single crystals whose structures were determined by X-ray crystallography. Lehn-type circular helicates generally only form with tris-bipy ligand strands and Fe(II) (and, in some cases, Ni(II) and Zn(II)) salts, so such architectures become accessible for other metal cations only through the use of knotted ligands. The different metalated knots all exhibit “second-sphere” coordination of a single chloride ion within the central cavity of the knot through CH···Cl– hydrogen bonding and electrostatic interactions. The chloride binding affinities were determined in MeCN by isothermal titration calorimetry, and the strength of binding was shown to vary over 3 orders of magnitude for the different metal-ion–knotted-ligand second-sphere coordination complexes.
Mutations of the epigenetic enzymes isocitrate dehydrogenase (IDH) 1 and 2, and the methylcytosine dioxygenase ‘ten–eleven translocation 2’ (TET2), are common in human myeloid malignancies and ...drivers of these disorders but the underlying mechanisms remain obscure. This review examines mutant IDH1/2 and TET2 enzymes in the context of responses to DNA damage and their potential involvement in age-related genomic instability. The clinical relevance of these findings and their potential application in novel therapeutic strategies is also discussed.
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