Allosteric coextraction of sodium and metal ions with calix[4]arene derivatives 2: First numerical evaluation for the allosteric effect on alkali metal extraction with crossed carboxylic acid type calix[4]arenes

► New preparation of crossed carboxylic acid types of calix[4]arene derivatives with two longer carboxylic acids and two acetic acids at the distal position. ► Solvent extraction of alkali metal ions in individual and competitive systems. ► First numerical evaluation for extraction constants as the allosteric effect on alkali metal extraction. ► Elucidation of the allosteric effect by using extraction data and 1H NMR spectra.