Hydrogen-bonded networks in 5-chloropyridin-2-amine-fumaric acid (2/1) and 2-aminopyridinium DL-malate.

Crystals of 5-chloropyridin-2-amine-(2E)-but-2-enedioate (2/1), 2C(5)H(5)ClN(2).C(4)H(4)O(4), (I), and 2-aminopyridinium DL-3-carboxy-2-hydroxypropanoate, C(5)H(7)N(2)(+).C(4)H(5)O(5)(-), (II), are built from the neutral 5-chloropyridin-2-amine molecule and fumaric acid in the case of (I) and from ring-N-protonated 2-aminopyridinium cations and malate anions in (II). The fumaric acid molecule lies on an inversion centre. In (I), the neutral 5-chloropyridin-2-amine and fumaric acid molecules interact via hydrogen bonds, forming two-dimensional layers parallel to the (100) plane, whereas in (II), oppositely charged units interact via ionic and hydrogen bonds, forming a three-dimensional network.