Supramolecular Sr(II) Complexes with Cucurbituril

Five new supramolecular compounds containing strontium–cucurbituril complexes are synthesized: [{Sr(H2O)5}2(CB[6])]Cl4·2NH4Cl·5H2O (1), [{Sr(H2O)3Cl}3(CB[6])2]Cl3·10H2O (2), [{Sr2(H2O)10}{Sr(H2O)4Cl}2(CB[6])2]Cl6·18H2O (3), [{Sr2(H2O)9}{Sr(H2O)4Cl}2(CB[6])2]Cl6·18H2O (4), [Sr(H2O)4(dmf)(CB[6])][Sr(H2O)3(dmf)(CB[6])(H2btc)](btc)·18H2O (5). According to single crystal X-ray diffraction data, the strontium atom adopts coordination number 8 in all compounds. The crystal structures of 1-4 compounds contain cationic polymeric chains in which cucurbituril molecules alternate with mono- and/or dinuclear strontium aqua complexes. Compound 5 contains two types of cationic strontium–cucurbit[6]uril complexes: [Sr(H2O)3(dmf)(CB[6])(H2btc)]+ and [Sr(H2O)4(dmf)(CB[6])]2+. They alternate in a checkerboard fashion to form slightly corrugated layers. A noteworthy feature of the structure of 5 is that the coordinated DMF molecule is located in the inner cavity of the macrocyclic cavitand. Compounds 1-5 are characterized by single crystal X-ray diffraction, IR spectroscopy, and the elemental analysis.