The synthesis of novel 4-(3,4-dimethoxyphenyl)chromenone-crown ethers and their cation binding,as determined using fluorescence spectra

o-Dihydroxy-4-(3,4-dimethoxyphenyl)-chromenones (coumarins; 3a,b) were synthesised from 1,2,3-trihydroxy- or 1,2,4-triacetoxybenzenes through a reaction with ethyl 3-(3,4-dimethoxyphenyl)-3-oxopropanoate in H₂SO₄ or CF₃COOH. The chromenone-crown ethers (4a–f) were prepared from the cyclic condensation of o-dihydroxy-4-(3,4-dimethoxyphenyl)chromenones (3a,b) with poly(ethylene glycol) ditosylates, in the presence of CH₃CN/alkali carbonates. The chromatographically purified original chromenone-crown ethers were identified by ¹H NMR, ¹³C NMR, MALDI-TOF mass spectrometry and elemental analysis. The 1:1 binding constants of Li⁺, Na⁺ and K⁺ with the chromenone-crown ethers were estimated in acetonitrile using fluorescence emission spectroscopy. The complexing-enhanced fluorescence spectra and complexing-enhanced quenching fluorescence spectra, along with the cationic recognition rules of the crown ethers allowed the ion binding powers to be determined.