Mono crown calix arenes

Electrospray Ionization/Mass Spectrometry (ES/MS), a soft-ionization desorption technique using polar solvents such as water, methanol, or acetonitrile, was used for direct measurement of cations in solution. The first measurements carried out with mono or bis(crown-6) calix[4]arenes from an equimolar cation-extractant solution confirm that the calixarenes mono(crown-6) extract only one cesium cation. On the contrary, in the same conditions, bis(crown-6) calix[4]arenes can extract two cesium cations for a ratio Cs/BC6 equal to 2.5. The binuclear complex (composed of two cesium cations) is the major species. Cesium/sodium selectivity measurements implementing various mono or bis(crown-6) calix[4]arenes were in agreement with liquid/liquid results.42... 

BOBCalixC6 was chosen as the preferred extractant for the CSSX solvent on the basis of synthetic accessibility, solubility characteristics, and selectivity. Calix[4]arene-crown-6 compounds may be synthesized with one or two crown loops, and both mono-and bis-crown calixes have good Cs+ extraction strength [9-16],... 

Various examples are known for all possible bis-crown ether derivatives from calix[4]arenes l,2 3,4-bis-crowns in the cone (39) and 1,2-alternate (40) and 1,3 2,4-bis-crowns in the 1,3-alternate conformation (41). Figure 5 gives a survey. Especially, the latter series is weU developed, comprising examples with identical and different ether loops, including structures describable as calixcryptands (41g). Compounds 41a (n = 6) were studied as ligands for the removal of caesium from nuclear wastes in analogy to their mono-crown counterparts in the 1,3-alternate conformation (37) . The 1,2 3,4-bis-crown-3 (39a, n = 3), on the other hand, is an important building block, since its calix[4]arene skeleton is fixed in a nearly perfect C4v-symmetrical cone conformation. ... 

Most of the inherently chiral calix[5]arenes described up to now, owe their chirality, however, to the asymmetric substitution pattern at the narrow rim, and due to the lack of other general, selective derivatization reactions are derived from 1,2-or 1,3-crown ethers. Both compounds possess a symmetry plane and can be desymmetrized by a single O-alkyl or O-acyl residue in position 3 (=5) or 4 (=5).151,152,153 In practice, 1,2-crown ethers 79 were prepared from mono-O-alkyl derivatives by reaction with the appropriate ditosylates, while 80 was obtained from the 1,3-crown-ether by subsequent O-alkylation or O-acylation using a weak base to benefit from the fact, that the first deprotonation leads to a hydrogen-bonded (4/5)monoanion. The picolyl derivatives 79 (n = 2) were resolved by HPLC... 

Crown ethers 38 of calix[4]arenes have been also obtained by direct O-aUcylation with ditosylates" . Their mono- and 3,4-diether derivatives (partial cone) are inherently chiral " . 

Competitive Cs+ ion transport in PIMs using calix[4]arene-mono- and bis-crown-6 carriers was also studied. The calix-bis-crown 25 (Figure 22) exhibited slightly more efficient CS+ transport than with the monocrown 24 (Figure 22) since the diffusion coefficient of the Cs-24+ complex is only one-fourth that of Cs-25". The selectivity values (o cs/m) for Cs+ over K+, Na" ", U02 " , Pb " ", and Al + with carrier 24 were greater than that with carrier 25, a result that was attributed to the higher association constant of Cs+ with carrier 24 in the membrane solvent. 

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