Syntheses and Characterization of Chiral Zeolitic Silver Halides Based on 3‑Rings

The synthesis of chiral zeolites
remains a significant challenge because the primary tetrahedral building
units are achiral and weak interactions exist between the guest and
host frameworks. Here, we present the syntheses and characterization of three new chiral zeolitic halides, [H3­(Dabco)2]­Ag3X6 (X =
Br (1) or I (2), Dabco = 1,4-diaza­bicyclo­[2.2.2]­octane)
and [H2­(Dabco)]­[(Dabco)­Ag4I6] (3). Compounds 1 and 2 are isostructural, containing a 4-connected zeolitic framework
built up from 3-ring units, with high-charge [H3­(Dabco)2]3+ located in chiral cages. Compound 3 contains a similar zeolitic [Ag3I6]3– framework to that of 2, but a [Ag­(Dabco)]+ unit is incorporated in each 3-ring, with [H2­(Dabco)]2+ located in channels. These frameworks are chiral, representing
the first examples of chiral zeolitic halides. The chirality transference
of the frameworks for 1 and 2 was attributed
to the template effect of the chiral [H3­(Dabco)2]3+ through strong electrostatic interactions and
multiple hydrogen-bond interactions. For compound 3,
direct coordination interactions play important roles in the chirality
transference from the chiral Dabco ligand to the framework.