Chiral Templating in a Hybrid Chromium Chloride Hydrate.

The synthesis and characterization of three new hybrid metal halide hydrates in which mer -[Cr III Cl 3 (H 2 O) 3 ] 0 cocrystallizes alongside α-methylbenzylammonium chloride are described. The enantiomorphic crystals, (( R )-(+)-α-methylbenzylammonium) 2 ( mer -[CrCl 3 (H 2 O) 3 ])Cl 2 (( R )- 1 ) and (( S )-(-)-α-methylbenzylammonium) 2 ( mer -[CrCl 3 (H 2 O) 3 ])Cl 2 (( S )- 1 ), have C 222 1 space group symmetry and show mirrored circular dichroism signals. The racemate, ( rac -α-methylbenzylammonium) 2 ( mer -[CrCl 3 (H 2 O) 3 ])Cl 2 (( rac )- 1 ), adopts a polar structure with Cm space group symmetry in which enantiomers are related by mirror planes within organic bilayers. Alongside detailed crystallography and magnetism of each compound, the optical properties of the mer -[Cr III Cl 3 (H 2 O) 3 ] 0 unit are revisited. Understanding the intermolecular forces that stabilize each of these crystal structures lends insights into crystal engineering methodologies for stabilizing noncentrosymmetric hybrid metal halides.