Complexes between 1,1 '-binaphthyl-2,2 '-dicarboxylic acid and pyrazoles: A case of manual sorting of conglomerate crystals (triage)

The crystal and molecular structure of two salts, I and III, and one molecu lar complex, II, formed by combining 1,1'-binaphthyl-2,2'-dicarboxylic acid (BNDA) with pyrazole (3) and 3,5-dimethylpyrazole (4) has been determined by X-ray crystallography. The most striking feature is the spontaneous reso lution of the racemic BNDA host by co-crystallization with 4, an achiral gu est, to form the salt III. The absolute configuration of three manually sel ected crystals of In have been established by crystallographic methods. The two crystals formed by the (P)-enantiomer display a negative Cotton effect . C-13-CPMAS-NMR Spectroscopy has been used to compare the compounds obtain ed by crystallization with those prepared by mechanical grinding.