Synthesis of triple cyclam (1,5,9,12,16,20,24,27-octaazatricyclo[18.10.2.25,16]tetratriacontane) and its 36-membered analogue 1,5,9,13,17,21,25,29-octaazatricyclo[19.11.2.25,17]hexatriacontane and studies of their co-ordinating properties in solution and the solid state

Abstract

Reaction of cyclam (1,4,8,11-tetraazacyclotetradecane) with toluene-p-sulfonylazetidine has been shown to provide a means for appending a 3-toluene-p-sulfonylaminopropane unit to each of the four nitrogen atoms in high yield. The resulting compound has been used as a precursor for two new tricyclic macrocyclic ligands, 1,5,9,12,16,20,24,27-octaazatricyclo[18.10.2.2^5,16]tetratriacontane (tcoa-14) and 1,5,9,13,17,21,25,29-octaazatricyclo[19.11.2.2^5,17]hexatriacontane (tcoa-15) which were synthesized under Richman–Atkins conditions using the appropriate tosylated diol. Potentiometric titrations show that both ligands form mono- and bi-metallic complexes in solution, but only the latter could be isolated in the solid state. These bimetallic complexes are not effective at retaining anions in a bridging position between the two metal ions, probably due to the intermetallic distance {measured by X-ray crystallography as 5.24 Å on [Cu₂Cl₂(tcoa-14)]Cl₂} being too great. Formation constants of complexes of both ligands with Co²⁺, Cu²⁺, Zn²⁺, Cd²⁺ and Pb²⁺ were determined and indicate the sequential occupation of the two outer binding compartments of these tricycles.