The protonated form of 1,8-bis(dimethylamino)naphthalene (DMANTH(+)) consists of a rigid, aromatic framework, substituted by two amino groups that are connected by a strong, symmetric (on the NMR time-scale) hydrogen bond bridge. The reorientational motion of the molecule in dimethylformamide-d7 solution was characterized by T-1 and NOE measurements for aromatic C-13 nuclei. Treating the reorientation of DMANH(+) as anisotropic rotational diffusion of a rigid body, the diffusion tensor was determined with good accuracy. Measurements and interpretation of N-15 T-1 and NOE indicate that the proton transfer between potential minima in the hydrogen bond bridge is faster than the molecular reorientation.