Impact of flexible succinate connectors on the formation of tetrasulfonylcalix[4]arene based nano-sized polynuclear cages: structural diversity and induced chirality study

Abstract

The building of new supramolecular coordination containers, obtained through the linking of tetrasulfonylcalix[4]arene (3-4H) based transition metal tetra- or trinuclear clusters with succinic acid (suc), as a flexible aliphatic connector possessing high conformational mobility and rotational freedom, produced a variety of three different polynuclear species in the crystalline phase, which were characterized by single crystal and powder X-ray diffraction. In the case of Co^II and Ni^II cations, the formation of unique chiral-induced isomorphous supramolecular architectures, generated by interconnection of dimeric M₈-cages with the co-crystallized M(OH)₂DMF₄ neutral species via H-bonding, was observed. Moreover, it was found that, in contrast to what was observed with Ni^II cations, the use of cobalt(II) ions in the same multicomponent system, led to the formation of achiral M₈-cages which were characterized by the presence of both left- and right-handed succinic acid moieties within the supramolecular entity structure. Finally, the coordination of Zn^II cations with 3-4H and succinic acid produced the generation of dimeric M₆-cages where two trinuclear [Zn₃-3]²⁺ cationic clusters were bound by two succinic carboxylate units.