Three 2‐amino­purine derivatives

The structure of 2‐amino‐6‐chloro­purine, C₅H₄ClN₅, (I), comprises a flat mol­ecule, with all possible strong hydrogen‐bond donors and acceptors involved in the hydrogen‐bonding network. The structures of 2‐amino‐6‐(4‐chloro­phenylsulfanyl)­purine hemihydrate, C₁₁H₈ClN₅S·0.5H₂O, (II), and 2‐amino‐6‐(4‐methylphenylsulfanyl)purine 0.33‐hydrate, C₁₂H₁₁N₅S·0.33H₂O, (III), have two and three unique mol­ecules, respectively, and one water mol­ecule in their asymmetric units. Both (II) and (III) exhibit elaborate hydrogen‐bonding networks that involve the S (for both) and Cl for (II)] atoms in addition to the expected strong hydrogen‐bonding sites. Both structures also have offset‐stacking formations of the phenyl and purine rings.