Trinuclear Cage‐Like ZnII Macrocyclic Complexes: Enantiomeric Recognition and Gas Adsorption Properties |
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Authors: | Prof Jan Janczak Dr Daniel Prochowicz Prof Janusz Lewiński Dr David Fairen‐Jimenez Tomasz Bereta Prof Jerzy Lisowski |
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Institution: | 1. Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P.?O. Box 1410, 50‐950 Wroc?aw (Poland);2. Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01‐224 Warsaw (Poland);3. Department of Chemical Engineering & Biotechnology, University of Cambridge, Pembroke Street, Cambridge CB2 3RA (UK);4. Department of Chemistry, University of Wroc?aw, F. Joliot‐Curie?14, 50‐383 Wroc?aw (Poland) |
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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 1 2] 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 1 2] and Zn3 3 2] 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 ZnII ions. This structural similarity is manifested also by the gas adsorption properties of the free H3 1 macrocycle. Recrystallization of Zn3 1 2] 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 ZnII ions. |
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Keywords: | cage compounds macrocycles microporous materials self‐recognition zinc |
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