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UV-Vis and ESI MS/MS Study of Calix[4]arene Derivatives and Their Lanthanide Complexes

: Coordination properties of calix[4]arenes bearing substituents on the lower rim: tetraethyl ester (1), tetraethylamide (2), and newly synthesized tetraethylmethylamide derivative (3), towards selected lanthanide cations (La3+, Eu3+, Yb3+) were studied by spectrophotometric titrations. No complexation was observed with ester derivative, while amide derivatives formed 1:1 complexes and bound lanthanide cations very efficiently (lgKLa2 = 5.1 ; lgKEu2 ≥ 6 ; lgKYb2 ≥ 6 ; lgKLa3 ≥ 6 ; lgKEu3 ≥ 6 ; lgKYb3 ≥ 6). The ligands and complexes were also analysed by ESI MS and MS/MS spectrometry. Both inductive cleavage and proton rearrangement fragmentation reactions were observed. Corresponding fragmentation pathways were proposed. The results obtained by MS analysis were in accordance with those obtained by spectrophotometric titrations.

calixarenes, lanthanides, electrospray mass spectrometry, UV-Vis spectroscopy

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