LIGAND DESIGN AND METAL-ION RECOGNITION - THE INTERACTION OF COPPER(II) WITH A RANGE OF 16-MEMBERED TO 19-MEMBERED MACROCYCLES INCORPORATING OXYGEN, NITROGEN AND SULFUR DONOR ATOMS

The interaction of copper(II) with a series of quinquedentate macrocyc les incorporating nitrogen, oxygen, and/or sulfur donor atoms is repor ted. These ligands form part of a structural matrix in which a systema tic variation in donor atom pattern and ring size is present (and agai nst which structure-function relationships are more clearly seen). Sta bility constants for the 1 : 1 copper complexes have been determined i n 95% methanol (I = 0.1 mol dm-3, NEt4ClO4) at 25-degrees-C. The study demonstrates the extremely large stability differentials [up to 10(10 ) for copper(II)] that may be achieved through structural variation wi thin the ligand framework employed for this study. The contribution of the respective donor atom types to overall complex stability was foun d to follow the expected order of NH(aliphatic) > NH(anilino) > S > 0. Based on earlier X-ray studies, the molecular mechanics modelling of two representative examples is also reported.