Porous nickel and cobalt hexanuclear ring-like clusters built from two different kind of calixarene ligands – new molecular traps for small volatile molecules

Abstract

Two new isomorphous ring-like hexanuclear symmetrical coordination species ((2-2H)₂3₂M₆, M = Co, Ni) presenting a hollow cyclic structure were successfully designed through the molecular recognition between the in situ generated sulfonylcalix[4]arene (3) supported trinuclear clusters and flexible macrocyclic linkers based on the low rim appended calix[4]arene diacid derivative (2-4H), demonstrating a pincer-like shape. The obtained coordination compounds have been characterized from a structural point of view in the crystalline phase, revealing the formation of internal hydrophobic voids, passing through the hexameric units, and external voids, resulting from the packing of the complexes in the lattice. A slight structural transformation was evidenced upon air-drying, leading to the closure of external voids caused by the solvent release and also the solvent mobility within the network. The ability of the obtained desolvated solid-state hexanuclear species to take up small volatile molecules like H₂O, CH₃C(O)CH₃, MeOH and EtOH has been investigated by dynamic vapor sorption (DVS), showing their high affinity towards more polarizable molecules.