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Synthesis and Binding Properties of iiii (4i) Stereoisomers of Phosphonato Cavitands − Cooperative Effects in Cation Complexation in Organic Solvents
Author(s) -
Delangle Pascale,
Mulatier JeanChristophe,
Tinant Bernard,
Declercq JeanPaul,
Dutasta JeanPierre
Publication year - 2001
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/1099-0690(200110)2001:19<3695::aid-ejoc3695>3.0.co;2-9
Subject(s) - chemistry , combinatorial chemistry , stereochemistry , computational chemistry , organic chemistry
Syntheses and host‐guest properties of tetrabridged phosphorylated cavitands in their iiii ( 4i ) configurations are described. The tetraphosphonato cavitands 2 and 3 , with the four P=O bonds oriented inwards ( 4i stereoisomer) were prepared in 25% and 53% yields respectively, from the corresponding resorc[4]arenes, dichloro(phenyl)phosphane oxide and base. The formation of the 4i stereoisomers is solvent‐dependent and is attributable to the capability of an ammonium guest to form an inclusion complex. Only the iiio (3io) stereoisomer of 3 was isolated otherwise, in low yield. These phosphonato cavitands, in their 4i configurations, are particularly efficient extractants for metal ions. The free energies of complexation of 3 with alkali metal and ammonium cations in chloroform solution are in the range from −43.3 (Li + ) to −52.4 kJ mol −1 (CH 3 NH 3 + ). High binding constants, 1 H, 31 P and 133 Cs NMR studies in solution and single‐crystal X‐ray analysis clearly demonstrated that the aromatic cavity of the host and the four hard donor P=O groups act cooperatively to ensure the encapsulation of the cationic guests. In the solid, the 2· Cs + complex showed the Cs + ion inside the aromatic cavity, interacting strongly with the four phosphoryl groups. The 2· CH 3 NH 3 + complex showed the methyl group of the guest oriented inside the cavity, with the stability of the complex supported by a complex H bond pattern involving H 2 O molecules and the anion.