The self-association equilibrium, i.e. formation of noncovalent dimers; in two triphenylamine derivative TPD (N,N'-bis(3-methylphenyl)-N,N'-diphenylbenzidine) and mMTDAB (1,3,5-tri[(3-methylphenyl)phenylamino]benzene), in solution was evaluated by H-1 NMR. spectroscopy. The gas-phase energetics of the respective dimerization processes was explored by computational quantum chemistry: The results indicate that self-association is significantly more extensive in TPB than in TDAB. It is proposed that this fact helps to explain why TPB presents a stability, higher than expected in the liquid phase, which is reflected in a lower melting temperature, a less volatile liquid, and possibly a higher tendency to form a glass. These results highlight the influence of self-association on the phase equilibria and thermodynamic properties of pure organic substances.