Amitriptylinium picrate: conformational disorder.

In the structure of the title salt [systematic name: 3-(10,11-dihydro-5H-dibenzo[a,d][7]annulen-5-ylidene)-N,N-dimethylpropan-1-aminium 2,4,6-trinitrophenolate] of a tricyclic antidepressant, C(20)H(24)N+.C(6)H(2)N(3)O(7)-, the dimethylaminopropyl subunit possesses a classical static conformational disorder. The central cycloheptadiene ring adopts a bent conformation that is intermediate between boat and chair forms, leading to a butterfly shape for the hetero-tricyclic moiety. In a complementary fashion, donors from amitriptyline and acceptors from picrate form intermolecular C-H...O hydrogen bonds and N-H...O salt bridges. These hydrogen bonds cluster amitriptyline and picrate ions into a closed R4(4)(36) hetero-tetramer, whereas intermolecular C-H...pi interactions between amitriptyline ions cluster them into homo-dimers. Significant pi-pi stacking interactions are also observed between aromatic rings of amitriptyline and picrate, and these, combined with the C-H...pi interactions, associate molecules into linear arrays along the [111] direction.