Synthesis and Binding Properties of iiii (4i) Stereoisomers of Phosphonato Cavitands − Cooperative Effects in Cation Complexation in Organic Solvents

Abstract

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 solventdependent 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

Exclusive recognition of sarcosine in water and urine by a cavitand-functionalized silicon surface

“…Among them, tetraphosphonate cavitands are outstanding: Their complexation ability spans from positively charged inorganic and organic species (9) to neutral molecules (10). This diverse complexation ability is the result of three interaction modes, which can be activated either individually or in combination by the host according to the guest requirements: (i) multiple ion-dipole interactions between the inward facing P¼O groups and the positively charged guests (11); (ii) single or dual H bonding involving the P¼O groups (11,12); and (iii) CH-π interactions between a methyl group present on the guest and the cavity of the host (13).…”

“…S10). The downfield shift of P¼O signals is a clear indication of the participation of phosphonates in the guest complexation, whereas the upfield shift of the methyl residue is diagnostic of N-CH 3 inclusion into the cavity (11). Under the same conditions, glycine produced no detectable variation in the P¼O chemical shift (Fig.…”

Hydrogen bonding in phosphonate cavitands: Investigation of host-guest complexes with ammonium salts

“…Cavitands (Scheme 1) were prepared by following the published procedures [11,12,20]. For the nomenclature used, see reference [9b].…”

Synthesis of Partially Bridged Phosphonate and Thiophosphonate Resorcinarenes

“…Tetraphosphonate cavitand 2 is readily available following Dutasta's synthetic procedure [16]. In analogy to [iiii] tetrathiophosphonate cavitand 1, the treatment of compound 2 with 1,2-Dihydroxybenzene and K 2 CO 3 in DMF led to the abstraction of a variable number of P=O bridges depending on the number of equivalents of nucleophile used (Scheme 2).…”

“…Because of their high binding capabilities, P=O groups have been included in preorganized structures to increase the stability of the complexes thus formed. Dutasta and co-workers reported the synthesis and the study of the binding properties of tetrabridged phosphonated cavitands having all inward configuration of the P=O groups [16]. To ensure strong binding, the P=O groups must be oriented toward the cavity (indicated as [iiii]).…”