Investigations of chiral host guest chemistry are
important to explore recognition in confined environments. Here, by
synthesizing water-soluble chiral porous nanocapsule based on the inorganic metal-oxo
Keplerate-type cluster, {Mo<sub>132</sub>} with chiral lactate ligands with the
composition [Mo<sub>132</sub>O<sub>372</sub>(H<sub>2</sub>O)<sub>72</sub>(<i>x-</i>Lactate)<sub>30</sub>]<sup>42-</sup> (<i>x</i> = D or L), it
was possible to study the interaction with a chiral guest, L/D-carnitine
and (<i>R</i>/<i>S</i>)-2-butanol in aqueous solution. The enantioselective recognition was
studied by quantitative <sup>1</sup>H NMR and <sup>1</sup>H DOSY NMR which
highlighted that the chiral recognition is regulated by two distinct sites. Differences
in the association constants (K) of L-
and D-carnitine, which,
due to their charge, are generally restricted from entering the interior of the
host, are observed, indicating that their recognition predominantly occurs at
the surface pores of the structure. Conversely, a larger difference in
association constants (K<i><sub>S</sub></i>/K<i><sub>R</sub></i> = 3) is observed for
recognition within the capsule interior of (<i>R</i>)-
and (<i>S</i>)-2-butanol.
Synthesis of homochiral zeolitic metal–organic frameworks with amino acid and tetrazolates for chiral recognition