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-cyclo­hexyl-3-hy­droxy-3-phenyl­prop­yl)piperidin-1-ium] 4-nitro­benzoate, C(20)H(32)NO(+)·C(7)H(4)NO(4) (−) (I), trihexyphenidylium 4-hy­droxy­benzoate, C(20)H(32)NO(+)·C(7)H(5)O(−) (II), trihexyphenidylium 4-bromo­benzoate, C(20)H(32)NO(+)·C(7)H(4)BrO(2) (−) (III), and trihexyphenidylium thio­phene-2-carboxyl­ate hemihydrate, 2C(20)H(32)NO(+)·2C(5)H(3)O(2)S(−)·H(2)O (IV), con­ducted 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 thio­phene-2-carboxyl­ate anions. Structure II is a non-merohedric twin by a twofold rotation about [403]. The main supra­molecular 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 mol­ecule 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 inter­actions are observed, plus C—H⋯Br close contacts for III.