Self-Sorting in the Formation of Metal-Organic Nanotubes: A Crucial Role of 2D Cooperative Interactions.

A mixture of ferrocene-based tetratopic pyridyl ligands FcL1 and FcL2 undergoes self-sorting upon competitive coordination with AgBF4, affording homomeric nanotubes FcNT1 and FcNT2 as a mixture. No mutual interference for the nanotubular growth occurred between FcNT1 and FcNT2 even when one of these ligands was used in large excess with respect to the other. 2D X-ray diffraction analysis of unidirectionally oriented nanotube samples, prepared by using the capillary technique, revealed that although FcL1 as reported previously stacks helically in the resulting nanotube FcNT1 FcL2 prefers to stack with no discernible helical twist in FcNT2. Such a difference in their stacking geometries is most likely a major reason for why mixed-ligand metal-organic nanotubes are not constructed upon competitive coordination of FcL1 and FcL2 with AgBF4.