Abstract
Tetra-CMP(O)-functionalized cavitands are very effective europium(III) extractants. Cavitand 1b is the strongest ligand and has the highest extraction constant for 1:1 complexation with Eu(picrate)3 (viz. Kex 1 = 2.7 × 1012M−4). The conformational behavior of the CMP(O) cavitands 1a,b and 2a,b was studied by means of NMR spectroscopy. The introduction of an N-propyl substituent imposes large conformational differences due to inhibition of the free rotation around the amide N-C(O) bond. The Gibbs free energy of activation is about 75 kJ/mol for a rotation around the amide moiety (inwardoutward motion). The N-propyl-substituted cavitands form clusters; this aggregation originates from the association of propyl and pentyl chains of the cavitand molecules. The ability of bromomethylcavitand 3 to complex solvent molecules (e.g. CH2C12 or toluene) in the cavity is illustrated by a single crystal X-ray structure (with CH2C12).
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References and Notes
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Boerrigter, H., Verboom, W., Hulst, R., Van Hummel, G.J., Harkema, S., Reinhoudt, D.N. (1999). Study of Conformational Behavior of CMP(O)-Cavitands by NMR Spectroscopy and X-Ray Analysis in Relation to the Extraction Properties. In: Pons, M. (eds) NMR in Supramolecular Chemistry. NATO ASI Series, vol 526. Springer, Dordrecht. https://doi.org/10.1007/978-94-011-4615-9_2
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DOI: https://doi.org/10.1007/978-94-011-4615-9_2
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