Chemistry of polydentate ligands. Part 6. Synthesis, characterisation, and properties of Group 2B cation complexes with novel quinquedentate macrocyclic ligands

Abstract

Complexes of quinquedentate macrocyclic ligands with Group 2B cations have been prepared by condensation of 2,6-diformylpyridine and 2,6-diacetylpyridine with 2,9-di(1-methylhydrazino)-1,10-phenanthroline monohydrochloride in the presence of metal-ion templates. Electrical conductivity measurements, i.r. and ¹H n.m.r. spectral data are reported and evaluated to show that ring closure rather than polymer formation has occurred. Evidence is presented for some metal ions in the macrocyclic complexes having pentagonal-pyramidal co-ordination geometries. The n.m.r. data are interpreted as indicating the presence of ring currents in the ligands. Hydrogenation of the hydrazone bonds produces two new ligands: the n.m.r. spectra of the zinc (II) complexes demonstrate that these macrocyles are folded. Relative yields of optical isomers of the complex with one of these reduced macrocycles are reported.