Ligand design and metal-ion recognition. The interaction of copper(II) with a range of 16- to 19-membered macrocycles incorporating oxygen, nitrogen and sulfur donor atoms

Abstract

The interaction of copper(II) with a series of quinquedentate macrocycles incorporating nitrogen, oxygen, and/or sulfur donor atoms is reported. These ligands form part of a structural matrix in which a systematic variation in donor atom pattern and ring size is present (and against which structure–function relationships are more clearly seen). Stability constants for the 1 : 1 copper complexes have been determined in 95% methanol (I= 0.1 mol dm–3, NEt4ClO4) at 25 °C. The study demonstrates the extremely large stability differentials [up to 1010 for copper(II)] that may be achieved through structural variation within the ligand framework employed for this study. The contribution of the respective donor atom types to overall complex stability was found to follow the expected order of NH(aliphatic) > NH(anilino) > S > O. Based on earlier X-ray studies, the molecular mechanics modelling of two representative examples is also reported.