Chalcogen bonds provide supramolecular association of beta-octamolybdate and chalconium cations

The interactions of triple σ-(QIV)-hole donating chalconium cations ([Q(bPh)R]+, when Q = S, Se, and Te) with nucleophilic beta-octamolybdate ([β-Mo8O26]4−) result in supramolecular association. The main focus of such assembly is on σ-(QIV)-hole recognition by the molybdate in cations with a biphenyl aromatic fragment. This leads to a remarkable diversity of the association patterns producing: (i) neutral 4 : 1 {[Q(bPh)R]4[β-Mo8O26]} complexes with cations stacked by π-π interactions; (ii) (Bu4N)+, [Q(bPh)R]+ and [β-Mo8O26]4− complexes of 2 : 2 : 1 stoichiometry with π-π interactions; (iii) (Bu4N)+, [Q(bPh)R]+ and [β-Mo8O26]4− complexes of a 2 : 2 : 1 stoichiometry without π-π interactions; and (iv) {[Q(bPh)R]2}2[β-Mo8O26] salts with π-π stacked cations but lacking any (QIV)⋯O interactions. Moreover, interactions in the system can drive the reorganization of [β-Mo8O26]4− into [α-Mo8O26]4−. The halogen-bonded (QIV)⋯O {(Q(bPh)R)x[β-Mo8O26]4−} (x = 2 and 4) assemblies, π-π stacked cationic dimers {(Q(bPh)R)2}2+ and complicated associates based on both types of interactions have been the subjects of crystallographic and computational studies. © 2024 The Royal Society of Chemistry.