The structures of uncommon cationic N-alkenyl purine and pyrimidine bases

The structures of 1,3 bis-(allyl)cytosinium bromide (1), 7,9 bis-(allyl)adeninium bromide hydrate (2) and 3-(butenyl)adeninium bromide (3) have been determined. 1 is dimeric via N-H...Br hydrogen bonds, which further associate into ribbons via weaker C-H...Br interactions. 2 is also dimeric, now from N-H...N hydrogen bonds, which build up further through a complex array of hydrogen bonds involving both the anion and water of crystallization (O-H...N, O-H...Br, C-H...Br). 3 does not dimerise but forms polymeric sheets via a series of N-H...N, C-H...N and C-H...Br hydrogen bonds.