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

The interactions of triple sigma-(QIV)-hole donating chalconium cations ([Q(bPh)R]+, when Q = S, Se, and Te) with nucleophilic beta-octamolybdate ([beta-Mo8O26]4-) result in supramolecular association. The main focus of such assembly is on sigma-(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[beta-Mo8O26]} complexes with cations stacked by pi-pi interactions; (ii) (Bu4N)+, [Q(bPh)R]+ and [beta-Mo8O26]4- complexes of 2 : 2 : 1 stoichiometry with pi-pi interactions; (iii) (Bu4N)+, [Q(bPh)R]+ and [beta-Mo8O26]4- complexes of a 2 : 2 : 1 stoichiometry without pi-pi interactions; and (iv) {[Q(bPh)R]2}2[beta-Mo8O26] salts with pi-pi stacked cations but lacking any (QIV)& ctdot;O interactions. Moreover, interactions in the system can drive the reorganization of [beta-Mo8O26]4- into [alpha-Mo8O26]4-. The halogen-bonded (QIV)& ctdot;O {(Q(bPh)R)x[beta-Mo8O26]4-} (x = 2 and 4) assemblies, pi-pi 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.