Crystal structures and Hirshfeld surface analyses of 2-[(4,6-di-amino-pyrimidin-2-yl)sulfan-yl]-N-(pyridin-2-yl)acetamide and 2-[(4,6-di-amino-pyrimidin-2-yl)sulfan-yl]-N-(pyrazin-2-yl)acetamide.

In the title compounds, C(11)H(12)N(6)OS (I) and C(10)H(11)N(7)OS (II), the di-amino-pyrimidine ring makes dihedral angles of 71.10†(9)° with the pyridine ring in (I) and 62.93†(15)° with the pyrazine ring in (II). The ethanamine group, -CH(2)-C(=O)-NH- lies in the plane of the pyridine and pyrazine rings in compounds (I) and (II), respectively. In both compounds, there is an intra-molecular N-H⋯N hydrogen bond forming an S(7) ring motif and a short C-H⋯O inter-action forming an S(6) loop. In the crystals of both compounds, mol-ecules are linked by pairs of N-H⋯N hydrogen bonds, forming inversion dimers with R(2)(2)(8) ring motifs. In (I), the dimers are linked by N-H⋯O and N-H⋯N hydrogen bonds, forming layers parallel to (1[Formula: see text] [Formula: see text]). The layers are linked by offset π-π inter-actions [inter-centroid distance = 3.777†(1)†à ], forming a three-dimensional supra-molecular structure. In (II), the dimers are linked by N-H⋯O, N-H⋯N and C-H⋯O hydrogen bonds, also forming a three-dimensional supra-molecular structure.