Disappearance of intramolecular stacking due to one-atom movement or increment of a 'propylene linker' in pyrazolo[3,4-d]pyrimidine-based flexible models.

In the crystal structures of 4,6-dimethylthio-1-[3-(4, 6-dimethylthio-2H-pyrazolo[3, 4-d]pyrimidin-2-yl)propyl]-1H-pyrazolo[3,4-d]pyrimidine, C(17)H(20)N(8)S(4), and 1-[4-(4-methoxy-6-methylthio-1H-pyrazolo[3, 4-d]pyrimidin-1-yl)butyl]-5-methyl-6-methylthio-4, 5-dihydro-1H-pyrazolo[3,4-d]pyrimidin-4-one, C(18)H(22)N(8)O(2)S(2), only intermolecular stacking due to aromatic pi-pi interactions between pyrazolo[3,4-d]pyrimidinerings is present.