Hydrogen bonding in 2-amino-4,6-dimethoxypyrimidine, 2-benzylamino-4,6-bis(benzyloxy)pyrimidine and 2-amino-4,6-bis(N-pyrrolidino)-pyrimidine: chains of fused rings and a centrosymmetric dimer

Molecules of 2-amino-4,6-dimethoxypyrimidine, C6H9N3O2, (I), are linked by two N-H...N hydrogen bonds [H...N 2.23 and 2.50 Angstrom, N...N 3.106 (2) and 3.261 (2) Angstrom, and N-H...N 171 and 145degrees] into a chain of fused rings, where alternate rings are generated by centres of inversion and twofold rotation axes. Adjacent chains are linked by aromatic pi-pi-stacking interactions to form a three-dimensional framework. In 2-benzylamino-4,6-bis(benzyloxy)pyrimidine, C25H23N3O2, (II), the molecules are linked into centrosymmetric R-2(2)(8) dimers by paired N-H...N hydrogen bonds [H...N 2.13 Angstrom, N...N 2.997 (2) Angstrom and N-H...N 170degrees]. Molecules of 2-amino-4,6-bis(N-pyrrolidino)pyrimidine, C12H19N5, (III), are linked by two N-H...N hydrogen bonds [H...N 2.34 and 2.38 Angstrom, N...N 3.186 (2) and 3.254 (2) Angstrom, and N-H...N 163 and 170degrees] into a chain of fused rings similar to that in (I).