A three-dimensional hydrogen-bonded framework in 2-amino-4,6-bis[N-methyl-N-(4-methylphenyl)amino]pyrimidine-5-carbaldehyde and hydrogen-bonded sheets in 2-amino-4-(indolin-1-yl)-6-methoxypyrimidine-5-carbaldehyde.

The molecules of 2-amino-4,6-bis[N-methyl-N-(4-methylphenyl)amino]pyrimidine-5-carbaldehyde, C(21)H(23)N(5)O, (I), and 2-amino-4-(indolin-1-yl)-6-methoxypyrimidine-5-carbaldehyde, C(14)H(14)N(4)O(2), (II), which crystallizes with Z' = 2 in the space group P\overline{1}, exhibit polarized electronic structures. Molecules of (I) are linked by a combination of N-H...O, C-H...O and C-H...pi(arene) hydrogen bonds into a three-dimensional framework structure, while those of (II) are linked into sheets by a combination of two N-H...O hydrogen bonds and one N-H...pi(arene) hydrogen bond.