Hydrogen bonding in nitroaniline analogues: hydrogen-bonded sheets in 2-amino-4,6-dimethoxy-5-nitropyrimidine and pi-stacked hydrogen-bonded sheets in 4-amino-2,6-dimethoxy-5-nitropyrimidine.

In 2-amino-4,6-dimethoxy-5-nitropyrimidine, C(6)H(8)N(4)O(4), the molecules are linked by one N-H...N and one N-H...O hydrogen bond to form sheets built from alternating R(2)(2)(8) and R(6)(6)(32) rings. In isomeric 4-amino-2,6-dimethoxy-5-nitropyrimidine, C(6)H(8)N(4)O(4), which crystallizes with Z' = 2 in P-1, the two independent molecules are linked into a dimer by two independent N-H...N hydrogen bonds. These dimers are linked into sheets by a combination of two-centre C-H...O and three-centre C-H...(O)(2) hydrogen bonds, and the sheets are further linked by two independent aromatic pi-pi-stacking interactions to form a three-dimensional structure.