New Molecular Receptors with Cyclophosphazene Subunits: Synthesis, Reactivity, and Structure-Property Relationships |
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Authors: | Krystyna Brandt Iwona Porwolik-Czomperlik Mariola Siwy Teobald Kupka Robert A Shaw David B Davies Richard A Bartsch |
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Institution: | (1) Institute of Polymer Chemistry, Polish Academy of Sciences, 34 M. Curie-Sklodowska St., 41-800 Zabrze, Poland;(2) Department of Chemistry, Birkbeck College (University of London), Gordon House, 29 Gordon Square, London, WC1H OPP, UK;(3) Department of Chemistry and Biochemistry, Texas Tech. University, Lubbock, TX 79409-1061, USA |
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Abstract: | A series of hydrophopic ( 2 and 3) and new hydrophilic ( 4– 7) molecular receptors of the PNP-lariat ether with tetra-substituted cyclotriphosphazene subunits have been prepared by the complete nucleophilic substitution of chlorine atoms in the reactive PNP-crown precursor 1 with the respective sodium cation-paired oxyanions (phenoxy 2, -naphthoxy 3, and methoxytrioxyethylenoxy 4) and aliphatic amines (n-propylamine 5 aziridine 6, and pyrrolidine 7). Their structures were established by MS and 31P NMR spectroscopy and their metal ion complexing properties tested by a TLC method. Comparison of the complexation behaviour for ligands 1– 7 shows that the affinity for particular cations is strongly substituent-dependent and, in general, is significantly enhanced by cooperation of the side arm donor atoms (O or N) with the parent PNP-crown structure in the binding process. The remarkable affinity of some ligands for selected cations, in particular lithium, cesium, and silver ions, is interpreted in terms of structure-property relationships. |
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Keywords: | P-pivot lariat ethers synthesis nucleophilic substitution metal ion complexation molecular receptors |
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