Compound 3 was prepared by self-assembly of 1,3,5-pentanetriamine and aqueo
us formaldehyde in quantitative yield (Figure 1). This molecule can exist i
n four well-defined diamond-lattice conformations of symmetries D-2d, S-4.
C-2v and D-2d Low-temperature C-13 NMR spectroscopy indicates the existence
of three main conformers; their relative populations depend on the solvent
used. An extra set of low-intensity lines is also observed. A conformation
interconversion scheme is proposed; it involves two additional less popula
ted quasi-diamond-lattice intermediates derived from a helix compressed alo
ng its axis. One of these is trapped as a 1:2 clathrate with 1,4-dioxane; i
ts crystal structure is reported.