Tetramers helically stacked

However, one of the most intriguing examples in this field, which also demonstrates the power of diffusion NMR to characterize supramolecular systems obtained by self aggregation, is the assignment of the different species that prevail in solution following the reduction of 2,5,8,ll-tetra-tert-butylcycloocta[l,2,3,4-def-,5,6,7,8]bis-biphenylene (65) to its respective tetraanions [59]. In this sample, different species were observed and only diffusion NMR provided a proof, in conjunction with 2-D NOESY, that the different molecular species are indeed different helically-stacked anionic aggregates of 65. When NMR diffusion measurements were performed on the obtained solution, four different diffusion coefficients were found for the mixture. These coefficients that were assigned to the monomer, dimer, trimer and tetramer of 65 (Fig. 6.24). Based on Eq. (6.16) ... 

Fig. 3 Class A SPs. 1 Ureidopyrimidone-based linear chains2 porphyria-based linear chains I folic acid tetramers columnar stacks 4 actin double-helical chains5 helicene helical chains6 C3-symmetrical molecules forming helical columnar stacks . 7 uracyl or pyridine-terminated anthracene forming linear chains 8 surfactant micelles linear polymers 9 2,3,6,7,10,1 l-hexa(l,4,7-trioxoacetyltriphenylene) columnar stacks. ...

Fig. 5 Schematic illustration of the formation of the disk-shaped tetramers of de-oxyguanosine 7 and 8 by intermolecular hydrogen bonding and the subsequent stacking of the disks into helical columns in the presence of potassium ions...

---