engleski

Complexation of alkali-metal cations by fluorescent calix[4]arene diphenylanthracene derivatives

Considering that fluorimetry-based analytical methods are very sensitive, fast, and versatile, functionalization of calixarenes by fluorophores to obtain sensors for cations which provide a fluorescent response, either by quenching or by enhancement of fluorescence, is of great interest. Three derivatives were designed containing a cation-binding site formed by ester, primary- and secondary-amide groups in combination with a diphenylanthracene subunit responsible for the desired fluorescent response. The compounds were synthesized and their complexation with alkali-metal cations was studied by means of spectrophotometric, fluorimetric, and NMR titrations in acetonitrile/dichloromethane and methanol/dichloromethane solvent mixtures (φ = 0.5). L1 and L2 were proven to be efficient ligands for alkali-metal cations, forming complexes of 1:1 stoichiometry, with ester derivative showing somewhat higher affinity towards the studied cations compared to the amide one. In all cases, the complexation was accompanied by an increase in the intensity of fluorescence. It was expected that L3 would have the highest ability to bind cations, but changes in its UV and emission spectra upon complexation were, although reproducible, unfortunately too small to enable reliable determination of stability constants of the corresponding complexes. In all cases, the stabilities of the complexes were significantly lower in MeOH/CH2Cl2 solvent mixture than in MeCN/CH2Cl2.

caixarene ; fluorescence ; complexation

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