Crystal Engineering of a Chiral Crystalline Sponge That Enables Absolute Structure Determination and Enantiomeric Separation.

Chiral metal-organic materials (CMOMs), can offer molecular binding sites that mimic the enantioselectivity exhibited by biomolecules and are amenable to systematic fine-tuning of structure and properties. Herein, we report that the reaction of Ni(NO 3 ) 2 , S -indoline-2-carboxylic acid ( S -IDECH), and 4,4'-bipyridine (bipy) afforded a homochiral cationic diamondoid, dia , network, [Ni( S -IDEC)(bipy)(H 2 O)][NO 3 ], CMOM-5 . Composed of rod building blocks (RBBs) cross-linked by bipy linkers, the activated form of CMOM-5 adapted its pore structure to bind four guest molecules, 1-phenyl-1-butanol (1P1B), 4-phenyl-2-butanol (4P2B), 1-(4-methoxyphenyl)ethanol (MPE), and methyl mandelate (MM), making it an example of a chiral crystalline sponge (CCS). Chiral resolution experiments revealed enantiomeric excess, ee , values of 36.2-93.5%. The structural adaptability of CMOM-5 enabled eight enantiomer@ CMOM-5 crystal structures to be determined. The five ordered crystal structures revealed that host-guest hydrogen-bonding interactions are behind the observed enantioselectivity, three of which represent the first crystal structures determined of the ambient liquids R -4P2B, S-4P2B, and R -MPE.