Tripodal (N-alkylated) CMP(O) and malonamide ligands: synthesis, extraction of metal ions, and potentiometric studies


Janczewski, Dominik and Reinhoudt, David N. and Verboom, Willem and Malinowska, Elzbieta and Pietrzak, Mariusz and Hill, Clement and Allignol, Cecile (2007) Tripodal (N-alkylated) CMP(O) and malonamide ligands: synthesis, extraction of metal ions, and potentiometric studies. New Journal of Chemistry, 31 (1). pp. 109-120. ISSN 1144-0546

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Abstract:Tripodal ligands build on the C-pivot ( 9b–e, 13b–d, and 17a–d) and trialkylbenzene platforms ( 10a,b, 11, 12, 14a,b, and 18a,b) bearing (N-alkylated) carbamoylmethylphosphine oxide (CMPO), carbamoylmethylphosphonate (CMP), and malonamide moieties were synthesized. Extraction studies with Am3+ and Eu3+ show that in general there is a positive influence of the N-alkyl substituents in C-pivot CMP(O) ligands on the D(distribution) coefficients. The trialkylbenzene CMPO ligands 10a,b, 11, and 12 have considerably larger D coefficients than the corresponding C-pivot analogues 9a–e, although hardly having any selectivity, while N-alkylation gives rise to smaller D coefficients. Although less effective the extraction behavior of the C-pivot CMP analogues 13b–d shows more or less the same trend as the corresponding CMPO ligands 9b–e upon substitution of the carboxamide N-atom with different alkyl chains. The different malonamide ligands 17a–d and 18a,b are bad extractants, while N-alkylation makes them even worse. Potentiometric studies of CMP(O) and malonamide ligands in polymeric membranes on Pb2+, Cu2+, Ca2+, Mg2+, Na+, and K+ salts revealed that N-alkyl substituents increase the stability constants of ion–ionophore complexes compared to unsubstituted ligands. In polymeric membrane electrodes the ligands induce a selectivity pattern that differs significantly from the so-called Hofmeister series, giving the highest selectivity coefficients for UO22+ among all examined cations (Pb2+, Cu2+, Ca2+, Mg2+, Na+, K+).
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Copyright:© 2007 Royal Society of Chemistry
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Metis ID: 241357