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

The interactions of triple σ-(Q IV )-hole donating chalconium cations ([Q(bPh)R] + , when Q = S, Se, and Te) with nucleophilic beta-octamolybdate ([β-Mo 8 O 26 ] 4− ) result in supramolecular association. The main focus of such assembly is on σ-(Q IV )-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-Mo 8 O 26 ]} complexes with cations stacked by π-π interactions; (ii) (Bu 4 N) + , [Q(bPh)R] + and [β-Mo 8 O 26 ] 4− complexes of 2 : 2 : 1 stoichiometry with π-π interactions; (iii) (Bu 4 N) + , [Q(bPh)R] + and [β-Mo 8 O 26 ] 4− complexes of a 2 : 2 : 1 stoichiometry without π-π interactions; and (iv) {[Q(bPh)R] 2 } 2 [β-Mo 8 O 26 ] salts with π-π stacked cations but lacking any (Q IV ) O interactions. Moreover, interactions in the system can drive the reorganization of [β-Mo 8 O 26 ] 4− into [α-Mo 8 O 26 ] 4− . The halogen-bonded (Q IV ) O {(Q(bPh)R) x [β-Mo 8 O 26 ] 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. Organic-inorganic supramolecular associates of chalconium cations and beta-octamolybdate anion unlock the potential of lacunary type polyoxometalates to serve as noncovalent ligands in the comparison with classical coordination chemistry of POM.