P-Sulfonatocalix[8]arene coordinates sodium cations and forms host-guest complex with berberine: insight from crystal structure

ABSTRACT In this paper, we expand the utilisation of large and flexible macrocyclic host p-sulfonatocalix[8]arene (C8S) in building up solid state assemblies with both inorganic and organic cations. Upon coordination of sodium cations to all sulphonate groups of the macrocycle the 3-D coordination polymer is formed. The C8S adopts circular pleated loop conformation and macrocyclic molecules are assembled into stacks stapled by coordination to multiple sodium cations. The arrangement of the metallo-supramolecular assembly is pseudo-hexagonal. In the presence of organic cation berberine, the host-guest complex is favoured. Macrocycle adopts conformation without a substantial internal cavity with two of the benzenesulfonate groups being inclined towards the centre of the molecule. One host binds eight berberine guests in the grooves and clefts of the molecular surface of the macrocycle. C8S is a suitable host for berberine in the solid state, and such crystallisation-driven host-guest complexation has potential in expanding the library of berberine crystal forms. Graphical abstract