Macrocyclic 14-Membered-Ring Diketal Dilactams: Spectroscopic Studies and Conformational Analysis of Their Complexes with Divalent Cations
✍ Scribed by Anne-Gaëlle Valade; Dominique Harakat; Jacques Guyot; Olivier Laprévote; Denise Dugat
- Publisher
- John Wiley and Sons
- Year
- 2010
- Tongue
- English
- Weight
- 569 KB
- Volume
- 2010
- Category
- Article
- ISSN
- 1434-1948
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✦ Synopsis
Abstract
The complexation behaviour of four new 14‐membered‐ring diketal dilactam macrocycles towards some divalent cation perchlorates has been investigated. Stoichiometries and binding constants were determined by ^1^H NMR titration experiments. The structures of the complexes were studied by IR, NMR (^1^H and ^13^C) and electrospray mass spectrometry. ^13^C longitudinal relaxation time data allowed identification of the donor atoms involved in the complexation and provided information on the intramolecular mobility of the complexed ligands. Molecular modelling was also used to gain further insights into the conformational changes undergone by these molecules as a result of metal ligation. It was found that i. the macrocycles formed complexes of essentially 1:1 stoichiometry in the binding order Sr^2+^ ≥ Ca^2+^ > Mg^2+^ > Ba^2+^, ii. the coordination process caused conformational changes that resulted in cleavage of the hydrogen bonds in the ligand structure and a new orientation of the NH–CO bonds and iii. the coordination of the cations involved either all six oxygen atoms of the ligands or five of them, depending on whether the OMe groups were cis or trans, and probably two oxygen atoms from the ClO~4~^–^ counter‐anion.