The transient template effect: chromium(<scp>III</scp>)-directed syntheses of metal-free macrocyclic ligands and crystal structure of 1,11-bis(2′-hydroxyethyl)-4,8;12,16;17,21-trinitrilo-1,2,10,11-tetra-azacyclohenicosa-2,4,6,9,12,14,18,20-octaene hydrochloride tetrahydrate

Abstract

A range of metal-free quinquedentate macrocyclic ligands incorporating 2,2′-bipyridine or 1,10-phenanthroline donor groups has been prepared by the use of a chromium(III) transient template. The transient template effect is shown to be due to pH effects resulting from the presence of chromium(III) complexes in aqueous solution, rather than a process in which the open-chain ligands become co-ordinated to the metal centre. The crystal and molecular structure of a free macrocyclic ligand is reported, as is the preparation of some chromium(III) complexes of open-chain and macrocyclic complexes.