Trinuclear Cage‐Like Zn^II Macrocyclic Complexes: Enantiomeric Recognition and Gas Adsorption Properties

Abstract

Three zinc(II) ions in combination with two units of enantiopure [3+3] triphenolic Schiff-base macrocycles 1, 2, 3, or 4 form cage-like chiral complexes. The formation of these complexes is accompanied by the enantioselective self-recognition of chiral macrocyclic units. The X-ray crystal structures of these trinuclear complexes show hollow metal-organic molecules. In some crystal forms, these barrel-shaped complexes are arranged in a window-to-window fashion, which results in the formation of 1D channels and a combination of both intrinsic and extrinsic porosity. The microporous nature of the [Zn3 12 ] complex is reflected in its N2 , Ar, H2 , and CO2 adsorption properties. The N2 and Ar adsorption isotherms show pressure-gating behavior, which is without precedent for any noncovalent porous material. A comparison of the structures of the [Zn3 12 ] and [Zn3 32 ] complexes with that of the free macrocycle H3 1 reveals a striking structural similarity. In H3 1, two macrocyclic units are stitched together by hydrogen bonds to form a cage very similar to that formed by two macrocyclic units stitched together by Zn(II) ions. This structural similarity is manifested also by the gas adsorption properties of the free H3 1 macrocycle. Recrystallization of [Zn3 12 ] in the presence of racemic 2-butanol resulted in the enantioselective binding of (S)-2-butanol inside the cage through the coordination to one of the Zn(II) ions.

Solid‐State Gas Adsorption Studies with Discrete Palladium(II) [Pd2(L)4]4+ Cages

“…These results are similar to what has been observed with other metallosupramolecular cage materials. A discrete metallosupramolecular system reported by Yaghi and co‐workers bound 0.8 mol CO 2 per mol Cu I , while the metallomacrocycle of Lisowski and co‐workers encapsulated 1.4 mol per CO 2 per mol Zn II (273 K, 1 bar) . Very recently a tube‐like metallosupramolecular system from Donnelly and co‐workers was found to uptake 0.2 mol CO 2 per mol Zn II ion of the architecture (298 K, 1 bar)…”

“…In addition to solution studies of gas binding within metallosupramolecular assemblies there has been increasing interest in the solid‐state gas adsorption properties of discrete metallocages. Maverick and co‐workers, have shown that discrete copper(II)‐containing molecular squares will bind H 2 gas in the solid state, while the groups of Yaghi, Batten, and Lisowski have examined the interaction of H 2 , N 2 , and CO 2 with discrete metallocages.…”

Electronic and vibrational exciton coupling in oxidized trianglimines

“…Highly symmetrical, large‐ring poly‐aza chiral macrocycles are of considerable interest because of their applications as molecular building blocks, catalysts, gelators, and discriminating agents . The synthetic method providing such compounds relies on thermodynamically driven cycloimination of dialdehydes with vicinal diamines of the trans ‐1,2‐diaminocyclohexane or threo ‐1,2‐diphenyl‐1,2‐diaminoethane type .…”

One‐step Access to Resorcinsalens—Solvent‐Dependent Synthesis, Tautomerism, Self‐sorting and Supramolecular Architectures of Chiral Polyimine Analogues of Resorcinarene

“…The DCC‐based reversible cycloimination reaction emerges now as a convenient template‐free method providing shape‐persistent, optically pure polyimine macrocycles from structurally predisposed substrates . These polyazamacrocycles are further applied as chiral catalysts and ligands in stereoselective synthesis, as molecular receptors, or as organic porous materials . The use of racemic substrates in cycloimination reactions often provides complex mixtures of diastereoisomers.…”

“…[3] These polyazamacrocycles are further applied as chiral catalystsa nd ligands in stereoselectives ynthesis, as molecular receptors, or as organic porousm aterials. [4,5] The use of racemic substrates in cycloimination reactions often provides complex mixtures of diastereoisomers. Chiral self-sorting is achieved in those DCC-based reactions for which the products significantly differ in symmetry and hence in rotationale ntropy.…”