 Solution

Two molecules of the aminopyridine form a self-complementary dimer through two N–H···N contacts. In each direction, one exocyclic amino hydrogen is the donor and the pyridine ring nitrogen of the other molecule is the acceptor.

Orient the two amino/pyridine-N edges toward one another, as in the second panel of the original homodimer drawing. Each molecule donates one NH and accepts at one ring N; the second amino H remains available for additional packing contacts. The chlorine substituent is retained but is not one of the two principal donor–acceptor sites.