Structural Elucidation of the Mechanism of Molecular Recognition in Chiral Crystalline Sponges

Abstract

To gain insight into chiral recognition in porous materials we have prepared a family of fourth generation chiral metal–organic frameworks (MOFs) that have rigid frameworks and adaptable (flexible) pores. The previously reported parent material, [Co2(S‐mandelate)2(4,4′‐bipyridine)3](NO3)2, CMOM‐1S, is a modular MOF; five new variants in which counterions (BF4−, CMOM‐2S) or mandelate ligands are substituted (2‐Cl, CMOM‐11R; 3‐Cl, CMOM‐21R; 4‐Cl, CMOM‐31R; 4‐CH3, CMOM‐41R) and the existing CF3SO3− variant CMOM‐3S are studied herein. Fine‐tuning of pore size, shape, and chemistry afforded a series of distinct host–guest binding sites with variable chiral separation properties with respect to three structural isomers of phenylpropanol. Structural analysis of the resulting crystalline sponge phases revealed that host–guest interactions, guest–guest interactions, and pore adaptability collectively determine chiral discrimination.

An Ultrastable π–π Stacked Porous Organic Molecular Framework as a Crystalline Sponge for Rapid Molecular Structure Determination

“…Despite many aromatic rings, only one pair of anthracene rings take parallel-displaced π-stacking fashion to form double layered roof-floor-like formation, with an interplanar distance of 3.72 Å (Figure 1c and Supporting Information Figure S2a). Other phenyl and anthracyl rings form T-shaped π-Page 5 of 24 CCS Chemistry This article presented here has been accepted for publication in CCS Chemistry and is posted at the © 2021 Chinese Chemical Society.…”

“…The strategy perfectly solves the structure determination problem for hardly crystallized liquids and other stubborn non-crystallizing compounds, [8][9] and the absolute configuration confirmation of natural products, [10][11][12][13][14] as well as inspection of the transient intermediates in chemical reaction. [15][16] Until now, only a few cases of metal-organic frameworks (MOFs) 5,9,[17][18][19][20][21][22][23][24][25][26][27] have been proved for crystalline sponge platform. Typical strategies based on MOFs platforms rely primarily on weak interactions 5 or coordinative substitution 21 to induce crystalline order of the target molecules.…”

Crystalline Sponge Method: X‐ray Structure Analysis of Small Molecules by Post‐Orientation within Porous Crystals—Principle and Proof‐of‐Concept Studies

“…Zaworotko and co‐workers reported a chiral porous MOF, [Co 2 (( S )‐mandelate) 2 (4,4′‐bipyridine) 3 ]X 2 (X=CF 3 SO 3 − or NO 3 − ), that works as a chiral CS as well as a chiral stationary phase in chromatographic separation [81] . The group developed several derivatives with substituted mandelates for the chiral discrimination of the absorbed guests [82] . In this case, the guest chirality was relatively determined with respect to the known configuration of the ( S )‐mandelates installed in the host frameworks (Figure 8).…”

Induction of Chirality in a Metal–Organic Framework Built from Achiral Precursors

“…Chiral metal-organic frameworks (MOFs) have gained increasing attentions for their potential applications in enantioselective recognition, [13] catalysis, [14] separation, [15] and so on. [16] In order to obtain bulk homochirality,chemists tend to directly use chiral ligands to synthesize homochiral MOF materials.…”