Macrocyclic 14-Membered Ring Diketal Dilactams: Evaluation of their Divalent Cation Binding Properties |
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Authors: | Yvon Pointud Anne-Gaelle Valade Christelle Pointon Georges Jeminet Jose-Luis Beltran |
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Affiliation: | 1. Thermodynamique des Solutions et des Polymères, UMR CNRS , Université Blaise Pascal de Clermont-Ferrand , 6003 , Aubière , France;2. Synthèse et Etude de Systèmes à Intérêt Biologique , UMR CNRS, Université Blaise Pascal de Clermont-Ferrand , 24 avenue des Landais, 63177 , Aubière , France;3. Department de Quimica Analitica , Universitat de Barcelona , Diagonal 647, E-08028 , Barcelona , Spain |
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Abstract: | The binding abilities of a new class of 14-membered ring ligands bearing diketal dilactam functions were explored by UV-visible spectrophotometry. Their formation constants, determined in THF solution, showed appreciable complexation with divalent cations (stability order: Sr2+≥Ca2+>Zn2+≥Mg2+>Ba2+) whereas no association was observed with monovalent cations. The stoichiometry of the complexes formed was essentially 1:1 although sometimes a low percentage (<10%) of 1:2 (cation–ligand) species was detected. The corresponding formation constants determined by computation (STAR program) were in the range 1.5β 11<4.8 and 4.4β 12<7.1. They depend significantly on the nature of the substituents. In addition, solvent extractions carried out in a water–chloroform system showed the highest constants (log K ex) for the most substituted macrocycles 7b and 7c (norephedrine series) with a lipophilic skeleton. |
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Keywords: | Macrocyclic diketal dilactams Formation constants Divalent cation complexation UV-visible spectrophotometry |
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