Complexation of the lithium cation with N,N,N’,N’-tetracyclohexyl-1,2-phenylenedioxydiacetamide: experimental and theoretical study

Abstract

ABSTRACTOn the basis of extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium Li+ (aq) + 1·Na+ (nb) 1·Li+ (nb) + Na+ (aq) taking part in the two-phase water–nitrobenzene system (1 = N,N,N’,N’-tetracyclohexyl-1,2-phenylenedioxydiacetamide called Sodium ionophore III; aq = aqueous phase, nb = nitrobenzene phase) was determined as log Kex (Li+,1·Na+) = 0.7 ± 0.1. Further, the stability constant of the 1·Li+ complex in nitrobenzene saturated with water was calculated for a temperature of 25 °C: log βnb (1·Li+) = 8.1 ± 0.2. Finally, applying quantum mechanical DFT calculations, the most probable structures of the nonhydrated 1·Li+ and the hydrated 1·Li+·H2O cationic complex species were derived. In both of these complexes, the ‘central’ cation Li+ is bound by four bonding interactions to the corresponding four oxygen atoms of the parent ligand 1. Besides, in case of the 1·Li+·H2O complex, the considered hydrated structure is stabilised by one water molecule bound to the ‘central’ lithium cation.