Conformational dynamics of triple rotors: Tris(dimethylamino)methane, triisopropylamine, and related molecules

NMR spectra and their temperature-dependence are reported for tris(dimethylamino)methane (1), for tris(diethylamino)methane (2), for triisopropylamine (3), and for N,N-diisopropyl-3-pentylamine (4) and are discussed in terms of the conformations adopted and interconversion of these conformations, as indicated by molecular mechanics calculations. Solid state NMR spectra, obtained by freezing the neat liquids at low temperatures, were also used to support the conclusions of the conformational analysis. Proton NMR spectra of protonated forms of 3 and 4 were similarly analyzed. Less crowded triple rotors prefer a gauche, gauche, gauche conformation while more crowded ones adopt an anti, gauche, gauche arrangement.