Crystal structures of four organic salts of trihexyphenidyl at 90 K.

The syntheses and crystal structure studies of four organic salts of trihexyphenidyl, viz ., trihexyphenidylium [1-(3-cyclo-hexyl-3-hy-droxy-3-phenyl-prop-yl)piperidin-1-ium] 4-nitro-benzoate, C 20 H 32 NO + ·C 7 H 4 NO 4 - ( I ), trihexyphenidylium 4-hy-droxy-benzoate, C 20 H 32 NO + ·C 7 H 5 O - ( II ), trihexyphenidylium 4-bromo-benzoate, C 20 H 32 NO + ·C 7 H 4 BrO 2 - ( III ), and trihexyphenidylium thio-phene-2-carboxyl-ate hemihydrate, 2C 20 H 32 NO + ·2C 5 H 3 O 2 S - ·H 2 O ( IV ), con-ducted at 90 K are described. Structures I , II , and III are solvent free with one cation-anion pair per asymmetric unit, while IV crystallizes as a hemihydrate, having two cation-anion pairs and one water of crystallization in its asymmetric unit. Structures I and III exhibit configurational disorder of the cation. Structure IV also exhibits disorder, but only of the thio-phene-2-carboxyl-ate anions. Structure II is a non-merohedric twin by a twofold rotation about [403]. The main supra-molecular motifs in I , II , and III are similar R 2 2 (10) rings between cation-anion pairs, although their packing within the crystals is distinct. As a consequence of having two cation-anion pairs and a water mol-ecule in its asymmetric unit, the packing in IV is by far the most complex of the four structures, its hydrogen-bonding patterns being quite different from I , II , or III . In all the crystals studied, N-H⋯O, O-H⋯O, and C-H⋯O inter-actions are observed, plus C-H⋯Br close contacts for III .