2,4-diamino-5-(1-naphthyl)-3,5-diaza-1-azoniaspiro[5.5]undeca-1,3-diene chloride

The title salt, C18H22N5+.Cl-, is a member of a new series of lipophilic 4,6-diamino spiro-s-triazines which are potent inhibitors of dihydrofolate reductase. The protonated triazine ring deviates from planarity, whereas the cyclohexane ring adopts a chair conformation. A rather unusual hydrogen-bonding scheme exists in the crystal. There is a centrosymmetric arrangement involving two amino groups and two triazine ring N atoms, with graph-set R-2(2) (8) and an N...N distance of 3.098 (3) Angstrom, flanked by two additional R-3(2) (8) systems, involving two amino groups, a triazine ring N atom and a Cl- anion, with N...Cl distances in the range 3.179 (2)- 3.278 (2) Angstrom. Furthermore, the Cl- anion, the protonated triazine ring N atom and an amino group form a hydrogen-bonding system with graph-set R-2(1) (6).