Diastereoselective formation and optical activity of an M4L6 cage complex

Abstract

A chiral bridging ligand affords a single diastereoisomer of tetrahedral M4L6 cage complex in which the optical rotation of each ligand is increased by a factor of 5 on coordination.

Tris(pyridylmethylamino)cyclotriguaiacylene Cavitands: An Investigation of the Solution and Solid‐State Behaviour of Metallo‐Supramolecular Cages and Cavitand‐Based Coordination Polymers

“…[41] Indeed, a recent communication by Ward and coworkers reported the diastereoselective formation of an [M 4 L 6 ] tetrahedral cage using a chiral pyridyl-pyrazole ligand. [42] The most closely related structures to the [Ag 4 (4) 4 ] tetrahedra are an [Mn 4 L 4 ] tetrahedron with a podand borate ligand, [38] and a [Cu 8 L 4 ] tetrahedral structure, in which the calixresorcinarene ligands act as the vertices of a metallo-supramolecular tetrahedron. [16] The [Cu 8 L 4 ] tetrahedron has large triangular windows with dimensions of approximately 14 , whereas the stellated tetrahedron reported here has virtually no portals for the exchange of guest molecules.…”

Symmetry breaking in self-assembled M 4 L 6 cage complexes

“…Although the cavity of the largest cage structurally characterized herein, 1b (Fig. 4), is too small for even the smallest chiral guest, the methods outlined here demonstrate how larger asymmetrical cages, imprinted with stereochemical information (29,(32)(33)(34), might selectively encapsulate and asymmetrically transform low-symmetry, information-rich guest species.…”

“…Besides the fundamental interest in symmetry breaking mentioned above (1), an asymmetric capsule could achieve recognition of asymmetric substrates (28) and possibly catalyze asymmetric transformations (29). So far all reported metal-organic capsules have high symmetry (27,30,31), although in some cases they are chiral (29,(32)(33)(34), and specific guest molecules are observed to stabilize lower-symmetry structures (32,35). M 4 L 6 capsules are constructed from octahedrally coordinated metal ions and linear bis-bidentate ligands.…”

“…M 4 L 6 capsules are constructed from octahedrally coordinated metal ions and linear bis-bidentate ligands. Because each vertex is defined by a metal stereocenter (Δ or Λ), an M 4 L 6 structure can have T (ΔΔΔΔ/ΛΛΛΛ, homochiral), C 3 (ΔΔΔΛ/ΛΛΛΔ, heterochiral), or S 4 (ΔΔΛΛ, achiral) symmetry (36), with the homochiral cage being most commonly observed (33,(37)(38)(39)(40)(41)(42)(43). When the Tsymmetric configuration is adopted, all metal-to-metal distances are the same, avoiding strain potentially incurred by differences in these distances present in the C 3 -or S 4 -symmetric configurations (44).…”

Trimeric and hexameric calixarene-based capsules

“…Metal-directed self-assembly is an efficient method for the construction of large, three--dimensional supramolecular structures 40,41 which may encapsulate guest molecules and catalyze chemical reactions proceeding inside their cavities 42 ; among them the metal-bound cavitand assemblies have been intensively studied. [43][44][45] It was established that the self-assembly of rigid cavitands 30 and 31 with platinum complex 32 affords platinum coordinated trimeric capsules 33 and 34.…”