Hydrogen-bonded network in the trichloroacetate salts of 2-amino-5-chloropyridinium and 2-methyl-5-nitroanilinium monohydrate.

In the crystal structures of 2-amino-5-chloropyridinium trichloroacetate, C(5)H(6)ClN(2)(+).C(2)Cl(3)O(2)(-), (I), and 2-methyl-5-nitroanilinium trichloroacetate monohydrate, C(7)H(9)N(2)O(2)(+).C(2)Cl(3)O(2)(-).H(2)O, (II), the protonated planar 2-amino-5-chloropyridinium [in (I)] and 2-methyl-5-nitroanilinium [in (II)] cations interact with the oppositely charged trichloroacetate anions to form hydrogen-bonded one-dimensional chains in (I) and, together with water molecules, a three-dimensional network in (II). The crystals of (I) exhibit nonlinear optical properties. The second harmonic generation efficiency in relation to potassium dihydrogen phosphate is 0.77. This work demonstrates the usefulness of trichloroacetic acid in crystal engineering for obtaining new materials for nonlinear optics.