A trefoil knot coordinated to two lithium ions: synthesis and structure

The very tight dicopper(I) trefoil knot that contains 1,3-phenylene spacers between the 1,10-phenanthroline subunits could be fully demetallated under drastic conditions (large excess of KCN in refluxing acetonitrile), afford ing thus the disentangled knotted ligand in almost quantitative yield. This free molecular knot appeared very prompt to protonate or to bind to variou s ions in order to regenerate the stable "entwined" conformation. Lithium i n particular appeared to be ideal for occupying the tight empty coordinatin g sites of knot (K-84)(p). A new dilithium complex could be obtained almost quantitatively; its surprising stability allowed the determination of its molecular structure both by H-1 NMR and X-ray diffraction along with that a lso determined for its dicopper(I) precursor.