Conformational features of imipramine hydrochloride in aqueous solution as detected by 1H NMR relaxation analysis

Proton NMR measurements were performed and H-1-H-1 dipolar interaction energies were measured to delineate the conformation of imipramine in solution. Self-association of imipramine into dimers was observed and a dimerization constant of 12 l mol-1 was calculated. The motional correlation times for the monomer and the dimer were calculated at tau-cm = 0.18 ns and tau-cd = 0.36 ns, respectively. The geometry of the self-stacked dimer was analysed by measuring intermolecular dipolar cross-relaxation rates and interpreted in terms of the conformation of the aminoalkyl moiety.