Synthesis of some 3-phenyl chromenone-crown ethers and equilibrium studies on complexation with ion-pair extraction of sodium and potassium dyes

Abstract

6,7-Dihydroxy-3-phenyl- 2H-chromenones and 7,8-dihydroxy-3-(methoxyphenyl)- 2H-chromenones, o-dihydroxy-3-phenylcoumarins, were prepared from phenylacetic acid/2,4,5-trihydroxybenzaldehyde, methoxyphenylacetic acid/2,3,4-trihydroxybenzaldehyde in NaOAc/Ac 2O, respectively. 3-Aryl-6,7-dihydroxy- 2H-chromenone and 3-aryl-7,8-dihydroxy- 2H-chromenone reacted with the polyethylene glycol ditosylate in CH 3CN/Me 2CO 3 to afford 12-crown-4,15-crown-5, and 18-crown-6-chromenones. The purified products were identified with IR, 1NMR, low and high resolution mass spectroscopy and elemental analysis. Liquid–liquid extractive-spectrophotometric studies of sodium and potassium ion complexes of 3a– c, 4a– h coumarin-crown ethers and anionic dyes [4-(2-pyridylazo)-resorcinol monosodium salt monohydrate (SPAR), and sodium picrate (SP), and potassium picrate (PP)], as the counter ion are described. The overall extraction equilibrium constants for the 1:1 complexes of the above coumarin-crown ethers with sodium and potassium ions, between the organic solvent and water, have been determined at 25 °C. They were conducted in various solvent–water systems maintaining an identical initial cation concentration in water, [M 0 +] w, and a macrocyclic ligand concentration in the organic phase, [L 0] org, so that in all extractions [M 0 +] w:[L 0] org ratios were 1:1. An ion association complex formed between the alkali-crown ether complex ion and a dye anion was extracted into the CH 2Cl 2 organic solvent, and then the dye concentration of the separated aqueous phase was measured with an ultraviolet–visible spectrophotometer. According to the study, SPAR is the best associated dye with all the coumarin-crown ethers and the extracted dye occurs as the ion-pair complex. The extraction selectivity was interpreted quantitatively by the constituent equilibrium constants, i.e. K ext, the ion-pair extraction constant of ML + and A − in CH 2Cl 2.