Selective cation binding with cis,cis-1,3,5-trioxycyclohexyl based ligands: application to ion transport and electrochemical detection and assessment of complexation by electrospray mass spectrometry

Abstract

The synthesis is reported of two sets of oxa-amide ionophores based on 2-phenylglycerol and cis,cis-cyclohexane-1,3,5-triol, with ligand coordination numbers of four, five and six. Ionophores based on the hexadentate cyclohexyl triamide 9 show excellent Na⁺/K⁺ selectivity (-log K^pot_Na,K = 3.1), and the pentadentate analogue 10 shows good Li⁺/Na⁺ selectivity (-log K^pot_Li,Na = 2.2). Solution NMR and liquid–liquid extraction studies confirmed the formation of 1∶1 complexes and IR studies pinpointed the presence of amide binding. Ligands based on 2-phenylglycerol exhibited good Ca²⁺ selectivity which was highest for the hexadentate triamide, 6. Detailed ESMS studies revealed similar trends in ion-binding, performed under controlled conditions.