Yttrium and lanthanide (Ln = La and Gd) complexes with cucurbit[10]uril: crystals transforming from supramolecular frameworks to coordination nanotubes†
Abstract
We report the synthesis and characterization of yttrium (Y3+) and lanthanide (Ln = La3+ and Gd3+) complexes with cucurbit[10]uril (Q[10]) via a self-assembly approach in a 6 M HCl solution. Crystals transforming from the initially formed two-dimensional (2D) supramolecular frameworks to 1D coordination nanotubes were observed. The coordination of Y3+ ions with Q[10] first led to the formation of a compound, {Y4(H2O)24(Q[10])3}·12Cl·4H2O (Q[10]-Y1), with a 2D supramolecular structure built up with an octanuclear complex and metal-free Q[10] via extensive second-shell interactions. Through crystals transforming, Q[10]-Y1 gradually transformed to another compound, {Y6(H2O)20(Q[10])}·18Cl·9H2O (Q[10]-Y2), with a 1D nanotube structure. Similar crystals transforming from supramolecular frameworks to 1D coordination nanotubes (Q[10]-La and Q[10]-Gd) were also observed in La3+ and Gd3+ complexes with Q[10], suggesting the unique phenomenon is a common feature in the self-assembly of Q[10] complexes with lanthanide ions. The crystal structures of these compounds were revealed by synchrotron single crystal X-ray diffraction and compared to the existing lanthanide and actinide complexes with Q[10].