Resolution of Chiral, Tetrahedral M4L6 Metal−Ligand Hosts1

Davis, Anna V.; Fiedler, Dorothea; Ziegler, Marco; Terpin, and Andreas J.; Raymond, Kenneth N.

doi:10.1021/ja0764815

Cited by 145 publications

(125 citation statements)

References 33 publications

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“…30 Optically active three-dimensional cages with vertex metal atoms carrying achiral ligands in a chiral octahedral arrangement have been explored by Raymond and coworkers. 7,31,32 We now introduce the concept of face-based cage chirality, which has a different origin, as it is defined by the cage faces and not vertices or edges. Star connectors used to define cage faces are frequently propeller-shaped, with all arms attached to the central moiety twisted in the same sense.…”

Section: Introductionmentioning

confidence: 99%

Coordination-Driven Face-Directed Self-Assembly of Trigonal Prisms. Face-Based Conformational Chirality

et al. 2008

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The coordination-driven self-assembly of four different trigonal prisms from three equivalents of one of four different tetrapyridyl star connectors and six equivalents of a platinum linker dication in nitromethane is presented. This face-directed approach affords high yield without template assistance. The prisms have been characterized by multinuclear and DOSY NMR and dual ESI-FT-ICR mass spectrometry. The use of a conformationally chiral star connector leads to a conformationally chiral prism when connector arm ends attached to a vertex have a strongly correlated twist sense and chirality is communicated across polyhedral faces, edges and vertices. Molecular mechanics results suggest that in the smallest prism 3d collective effects dominate and the all-P and all-M conformers are strongly favored. NMR data prove that the two edges of the pyridine rings in the triflate salts of 3a -3d are distinct. An Eyring plot of rates obtained from lineshape analysis and 1-D EXCHSY NMR yields an activation enthalpy ΔH ‡ of ∼12 kcal/mol and activation entropy ΔS ‡ of ∼-15 cal/mol.K for the edge interconversion process, compatible with pyridine rotation around the Pt-N bond. For 3c, this behavior is observed only up to ∼318 K. At higher temperatures, the Eyring plot is again linear but follows a very different straight line, with ΔH ‡ of ∼35 kcal/mol and ΔS ‡ of ∼60 cal/mol.K. This highly unusual result is further investigated and discussed in the following companion paper.

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Section: Introductionmentioning

confidence: 99%

Coordination-Driven Face-Directed Self-Assembly of Trigonal Prisms. Face-Based Conformational Chirality

et al. 2008

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“…47 It was shown that the resolution of 6 is proton-dependent and relies on the asymmetric interaction of Snic + with the triscatecholate metal vertices at the exterior of the coordination assembly. 61 The resolved [Ga 4 (L) 6 ] cage 6 proved to be remarkably stable toward racemization even after replacement of the resolving agent by an achiral counter ion, providing the first example of a [M 4 (L) 6 ] capsule with chiral memory, 47 discussed in the following section. Different degrees of chiral induction could also be observed during the interaction of S-nic 4 ] capsules also based on catechol ligands.…”

Section: Diastereoselective Synthesismentioning

confidence: 97%

Stereochemical Communication within Tetrahedral Capsules

Ramsay¹,

Nitschke²

2013

Chemistry Letters

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The creation of isolated chirotopic environments that mimic enzyme binding pockets has been a long-term goal in supramolecular chemistry. Metalorganic cages with enclosed and defined inner spaces have proven useful for this purpose. Here, we provide a review of recent progress on understanding, and controlling the transmission of stereochemistry within [M 4 (L) 6 ] and [M 4 (L) 4 ] tetrahedral cages.

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“…14 This property enabled the determination of absolute configuration of the resolved enantioenriched parent assembly 1 by circular dichroism spectroscopy. 12 When assemblies 6-K12Ga4(R)-56 and 6-K12Ga4(S)-56 were examined by CD spectroscopy, the spectra of the two enantiomers proved to be perfect mirror images of each other and contain a shape and sign of the Cotton effect similar to those of ΔΔΔΔ-1 and ΛΛΛΛ-1 (see Supporting Information). 12 Thus, we infer by comparison and assign complex 6-K12Ga4(R)-56 as the ΔΔΔΔ stereoisomer and 6-K12Ga4(S)-56 as the ΛΛΛΛ stereoisomer.…”

Section: Scheme 1 -Synthesis Of Ligand (R)-5mentioning

confidence: 99%

“…Resolution of the racemate was realized using (-)-N'-methylnicotinium iodide, giving access to enantiopure ΛΛΛΛ-(S-nic  1) and ΔΔΔΔ-(S-nic  1) stereoisomers. 12 Sequential ion exchange chromatography with large excess amounts of tetramethylammonium and potassium iodides salts then afforded "empty" and enantiopure clusters. However, the instability of the isolated cationic guest-free or K + -filled ΛΛΛΛ-1 and ΔΔΔΔ-1 clusters warrant improvements.…”

mentioning

confidence: 99%

Chiral Amide Directed Assembly of a Diastereo- and Enantiopure Supramolecular Host and its Application to Enantioselective Catalysis of Neutral Substrates

et al. 2013

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The synthesis of a novel supramolecular tetrahedral assembly of K12Ga4L6 stoichiometry is reported. The newly designed chiral ligand exhibits high diastereoselective control during cluster formation, leading exclusively to a single diastereomer of the desired host. This new assembly also exhibits high stability toward oxidation or a low pH environment and is a more robust and efficient catalyst for asymmetric organic transformations of neutral substrates.

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Resolution of Chiral, Tetrahedral M₄L₆ Metal−Ligand Hosts¹

Cited by 145 publications

References 33 publications

Coordination-Driven Face-Directed Self-Assembly of Trigonal Prisms. Face-Based Conformational Chirality

Coordination-Driven Face-Directed Self-Assembly of Trigonal Prisms. Face-Based Conformational Chirality

Stereochemical Communication within Tetrahedral Capsules

Chiral Amide Directed Assembly of a Diastereo- and Enantiopure Supramolecular Host and its Application to Enantioselective Catalysis of Neutral Substrates

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