SYNTHESIS, STRUCTURE AND COMPLEXING CAPABILITIES OF N,N',N'',N'''-TETRAKIS(3-HYDROXYPROPYL)CYCLAM

The synthesis of the new pendant arm macrocyclic ligand N,N',N '',N tr iple prime-tetrakis(3-hydroxypropyl)cyclam (THPC-14) has been accompli shed, in quantitative yield, through the high pressure reaction of 1,4 ,8,11-tetraazacyclotetradecane (cyclam) with trimethylene oxide (oxeta ne). The molecular and crystal structure of this compound, which have been determined by X-ray crystallography, show the presence of both in tramolecular and intermolecular hydrogen bonding, the former of which, together with an RSSR pattern of chiralities at the nitrogen atoms (t he trans-IV configuration), preorganise the ligand unfavourably toward s complexation. Formation constants have been determined for complexes of the ligand with Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+ and Pb2+ by gla ss electrode potentiometry. In all cases the [M(THPC-14](2+) complex i s less stable than the complex formed from the related ligand N,N'N '' ,N triple prime-tetrakis(2-hydroxyethyl)cyclam (THEC-14), a fact which can be attributed to the formation of six-membered chelate rings by t he pendant arms rather than five-membered chelate rings. Isolation of the octahedral complexes [Ni(THPC-14)](ClO4)(2) and [Ni(THPC-14)(NCS)( 2)] and a study of their spectral and magnetic properties indicates th at pendant hydroxyl coordination occurs, but that this bonding is rela tively weak facilitating easy substitution by isothiocyanate.