Anion-directed assembly of macrocycle and helix

Self-assembly of the flexible ligand N, N'-bis(3-pyridylmethyl) thiourea (bpt) with ZnCl2 and CdCl2 in the absence and presence of KSCN yielded a short series of novel complexes (1-4) with macrocyclic, helical, double-helical, and 1D polymeric structures. Different metal ions, hydrogen bonds, and counteranions play significant roles in the final crystal structures. The NCS- anion was found to favor the formation of helical structures, whereas the Cl- anion favored macrocycle formation in the present system. Photoluminescence (PL) measurement results revealed that complex 2 (Zn( bpt)(SCN)(2)) with a helical structure exhibits enhanced emissions compared to those of the ligand and other complexes. The anion-directed assembly as well as the interesting emissions may provide useful information for further design of metal-organic compounds with novel structures and properties.