Solution complexation behaviour of 1,3,5-trioxycyclohexane based ligands and their evaluation as ionophores for Group IA/IIA metal cations

A new series of cis,cis-cyclohexane-1,3,5-triol derivatives bearing one, tw o and three carbamoylalkyl substituents is reported. Ring interconversion p romoted by intramolecular hydrogen bonding is observed for the mono- and di -alkylated derivatives 3 and 4 depending on solvent polarity. H-1 NMR param eters obtained have allowed the calculation of the Gibbs free energy change (Delta G(0)) for the trioxa- equatorial<->trioxa-axial equilibrium, modell ing the conformational changes promoted by ion binding. Selectivity coeffic ients have been assessed electrochemically using fixed interference methods for the detection of biologically relevant IA/IIA metal cations. Ionophore 4 displays a Nernstian response towards the detection of Ca2+ and logK(Ca, M)(pot) values are calculated. Solution NMR studies confirm the formation o f 1:1 complexes for 4 with lithium, while 2:1 complexation is favoured with Ca2+. Detailed ES-MS studies performed under controlled conditions reveale d similar trends in ion binding.