Cationic Tripodal Receptor Assisted Formation of Anion and Anion–Water Clusters: Structural Interpretation of Dihydrogen Phosphate Cluster and Sulfate–Water Tetramer [(SO₄)₂–(H₂O)₂]^4–

Well-defined anion and anion–water clusters based on tetrahedral oxyanions are reported herein. Self-assembled infinite dihydrogen phosphate anion clusters of 10 H2PO4– ions consist of a hexameric cluster linked to tetrameric and trimeric clusters. Octahedrally arranged discrete anionic [Na­(ClO4)6]5– cluster is found to stabilize by self-complementary H-bonding and electrostatic interactions in noncapsular complexes. Our findings also indicate the presence of discrete sulfate–hydrogen sulfate anion trimers [SO4(HSO4)2]4– and sulfate–water tetramers [(SO4)2(H2O)2]4– in the bimolecular capsular complexes of the tripodal receptor. All complexes were well characterized by FT-IR and NMR spectroscopies, TGA, DSC, and XRD.