Solvent‐Dependent Host–Guest Chemistry of an Fe<sub>8</sub>L<sub>12</sub> Cubic Capsule

Browne, Colm; Brenet, Simon; Clegg, Jack K.; Nitschke, Jonathan R.

doi:10.1002/ange.201208740

Cited by 26 publications

(18 citation statements)

References 85 publications

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“…The subcomponent self-assembly of 3,3′-diformyl-4,4′-bipyridine 30 and different anilines around Fe II ions thus yielded cubic structure 31 as confirmed by single-crystal X-ray diffraction (Figure 8). 44 Each metal center of Λ stereochemistry in 31 was adjacent to three Δ centers and vice versa, lending the capsule approximate T h point symmetry as opposed to the O (chiral octahedral) point symmetry found for other M 8 L 6 41−43 and M 8 L 12 48,49 cube structures. The T h -symmetrical arrangement for 31, which forces the bipyridine rings into an eclipsed coplanar configuration, appears to allow the ligands to bow slightly away from the Fe−Fe vectors, relieving strain more effectively than would be possible in an O-symmetric arrangement.…”

Section: Cubic Cagesmentioning

confidence: 99%

Stereochemistry in Subcomponent Self-Assembly

2014

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CONSPECTUS: As Pasteur noted more than 150 years ago, asymmetry exists in matter at all organization levels. Biopolymers such as proteins or DNA adopt one-handed conformations, as a result of the chirality of their constituent building blocks. Even at the level of elementary particles, asymmetry exists due to parity violation in the weak nuclear force. While the origin of homochirality in living systems remains obscure, as does the possibility of its connection with broken symmetries at larger or smaller length scales, its centrality to biomolecular structure is clear: the single-handed forms of bio(macro)molecules interlock in ways that depend upon their handednesses. Dynamic artificial systems, such as helical polymers and other supramolecular structures, have provided a means to study the mechanisms of transmission and amplification of stereochemical information, which are key processes to understand in the context of the origins and functions of biological homochirality. Control over stereochemical information transfer in self-assembled systems will also be crucial for the development of new applications in chiral recognition and separation, asymmetric catalysis, and molecular devices. In this Account, we explore different aspects of stereochemistry encountered during the use of subcomponent self-assembly, whereby complex structures are prepared through the simultaneous formation of dynamic coordinative (N → metal) and covalent (N═C) bonds. This technique provides a useful method to study stereochemical information transfer processes within metal-organic assemblies, which may contain different combinations of fixed (carbon) and labile (metal) stereocenters. We start by discussing how simple subcomponents with fixed stereogenic centers can be incorporated in the organic ligands of mononuclear coordination complexes and communicate stereochemical information to the metal center, resulting in diastereomeric enrichment. Enantiopure subcomponents were then incorporated in self-assembly reactions to control the stereochemistry of increasingly complex architectures. This strategy has also allowed exploration of the degree to which stereochemical information is propagated through tetrahedral frameworks cooperatively, leading to the observation of stereochemical coupling across more than 2 nm between metal stereocenters and the enantioselective synthesis of a face-capped tetrahedron containing no carbon stereocenters via a stereochemical memory effect. Several studies on the communication of stereochemistry between the configurationally flexible metal centers in tetrahedral metal-organic cages have shed light on the factors governing this process, allowing the synthesis of an asymmetric cage, obtained in racemic form, in which all symmetry elements have been broken. Finally, we discuss how stereochemical diversity leads to structural complexity in the structures prepared through subcomponent self-assembly. Initial use of octahedral metal templates with facial stereochemistry in subcomponent self-assembly, which predic...

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Section: Cubic Cagesmentioning

confidence: 99%

Stereochemistry in Subcomponent Self-Assembly

2014

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“…Because modification of the aldehyde or porphyrin structure might interfere with the cage formation, we decided to manipulate the counterion. [12] Replacing Fe(OTf) 2 with Fe(NTf 2 ) 2 resulted in cage compound 3 in 97 % yield (see the Supporting Information for characterization). Cage compound 3 proved to be soluble in acetone, acetonitrile, and DMF, as well as in solvent mixtures, for example, 1,2dichlorobenzene/acetonitrile or water/acetone.…”

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“…Styrenes with electron-donating groups gave the corresponding cyclopropanes in high yields (11,75%,TON= 302,d.r. = 77:23;12,88 %,TON = 351,d.r. = 76:24).…”

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Encapsulated Cobalt–Porphyrin as a Catalyst for Size‐Selective Radical‐type Cyclopropanation Reactions

Otte

Kuijpers

Troeppner

et al. 2014

Chemistry A European J

108

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A cobalt-porphyrin catalyst encapsulated in a cubic M8 L6 cage allows cyclopropanation reactions in aqueous media. The caged-catalyst shows enhanced activities in acetone/water as compared to pure acetone. Interestingly, the M8 L6 encapsulated catalyst reveals size-selectivity. Smaller substrates more easily penetrate through the pores of the "molecular ship-in-a-bottle catalysts" and are hence converted faster than bigger substrates. In addition, N-tosylhydrazone sodium salts are easy to handle reagents for cyclopropanation reactions under these conditions.

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“…The choice of p ‐anisidine was due to its high nucleophilicity and consequent stabilizing effect in the formation of imine bonds 15. The 1 H NMR spectrum of 1 (Figure 1) shows significant coordination‐induced shifts of the aromatic signals16 and confirmed quantitative formation of the imine‐based ligand through the appearance of a singlet at 8.22 ppm. ESI‐MS also confirmed the formation of 1.…”

Section: Methodsmentioning

confidence: 66%

Palladium‐Templated Subcomponent Self‐Assembly of Macrocycles, Catenanes, and Rotaxanes

2014

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The reaction of 2,6-diformylpyridine with diverse amines and Pd(II) ions gave rise to a variety of metallosupramolecular species, in which the Pd(II) ion is observed to template a tridentate bis(imino)pyridine ligand. These species included a mononuclear complex as well as [2+2] and [3+3] macrocycles. The addition of pyridine-containing macrocyclic capping ligands allows for topological complexity to arise, thereby enabling the straightforward preparation of structures that include a [2]catenane, a [2]rotaxane, and a doubly threaded [3]rotaxane.

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Solvent‐Dependent Host–Guest Chemistry of an Fe₈L₁₂ Cubic Capsule

Cited by 26 publications

References 85 publications

Stereochemistry in Subcomponent Self-Assembly

Stereochemistry in Subcomponent Self-Assembly

Encapsulated Cobalt–Porphyrin as a Catalyst for Size‐Selective Radical‐type Cyclopropanation Reactions

Palladium‐Templated Subcomponent Self‐Assembly of Macrocycles, Catenanes, and Rotaxanes

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Solvent‐Dependent Host–Guest Chemistry of an Fe8L12 Cubic Capsule

Cited by 26 publications

References 85 publications

Stereochemistry in Subcomponent Self-Assembly

Stereochemistry in Subcomponent Self-Assembly

Encapsulated Cobalt–Porphyrin as a Catalyst for Size‐Selective Radical‐type Cyclopropanation Reactions

Palladium‐Templated Subcomponent Self‐Assembly of Macrocycles, Catenanes, and Rotaxanes

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Solvent‐Dependent Host–Guest Chemistry of an Fe₈L₁₂ Cubic Capsule