Calixarene ligands

In 2012, Liao and coworkers [52] reported a Dy6 octahedron (24, Figure 3.17), seen as two edge-sharing [(p4-0)Dy4] tetrahedra, with two tail-to-tail calixarene ligands. The ac susceptibilities show obvious temperature-dependent both in-phase (x ) and out-of-phase (x") signals under a zero dc field, indicating multiple relaxation SMM behaviour. 

As for wide-rim CMPO calixarenes, the extraction ability for all the ada-mantyl-calixarene ligands is much better than for their monomeric analogues (CAdll, CAdl2) and DiOCMPO. 

The structural characterization of a mononuclear Eu-calix[6]arene complex reveals a more unusual complexation mode. In Eu(H4LXOHXDMF)6 (H6L = p-tm-butylcalix[6]arene Table 13) the Eu cation is placed outside the cavity forming only one monodentate bond to the calixarene ligand [193]. Six DMF molecules and most likely a hydroxyl group accomplish 8-coordination. The smaller sized calix[4]arene [194] and ether-extended bis(homooxa)-p-tert-... 

Fig. 19 Formation of the dimeric coordination capsule 28 based on the calixarene ligand 27. The helical twist results from the orientation of the meta-substituted pyridyl units upon coordination to palladium(II) ions (represented by grey spheres). Adapted with permission from [141]. Copyright 2001 American Chemical Society...

Subvalent germanium complexes combined with a dianionic calixarene ligand have been found. The reaction of / -tert-butylcalix[4] arene with MesSil in the presence of pyridine provides a useful synthetic route for [Butcalix ]H2. 

Other signiflcant complexes of this type, containing one or more lanthanides, are formed by calixarenes (see Calixarenes) Much of this work has been prompted by their potential in separating lanthanides from uranium and other metals. A calixarene ligand with two amide substituents has been synthesised as an extractant for lanthanides dimeric Sm and Eu and monomeric Eu complexes have been prepared. Another calixarene, with four phosphine oxides attached, has been fixed to silica particles and the resulting system has been found to give very efficient extraction of Eu + and Ce + from simulated waste. A calix[4]arene complex of Gd + binds... 

Figure 80 Crystal structure of (HN(C2H5)3)2[(UO2)2(C88Hi08O8)(OH)]-(N(C2H5)3)2-(H2O)3-(CH3CN)4 and of the calixarene ligand with the metal complex removed for clarity (Thuery, Keller et al. Acta Crystallogr.,...

The cavities of calixarenes can enclose small molecules ((11), Scheme 32). Electron-deficient fragments CpMv were bound to calixarene ligands with the aim to produce cavities with enhanced nucleophile binding capabilities.320 CpTaL for L114 /)-Bu -calix[4]arenc (11) exhibited... 

Encapsulation of the Eu3 + and Tb3 + ions by cage-like ligands was also achieved using functionalized calixarenes. Metal luminescence properties were studied mostly for complexes of calix[4]arenes, while few results are available for complexes of calix[6]arenes and calix[8]arenes, with the latter being dinuclear complexes. Figure 13 schematically shows the calixarene ligands of the Eu3+ and Tb3+ complexes examined. Some photophysical data and the number of coordinated solvent molecules of these complexes are gathered in Table 4. 

Recently, a new type of calixarene ligands, the calixcrowns, were examined for complexation of lanthanide ions. The calixcrowns 75 and 76 were synthesized and ligand 77 was obtained as a secondary product in the... 

FIGURE 25 The wavy moieties represent the contour of the calixarene ligands in [(H0)2(0C02)Eu4(calix[7])2(DMS0)6] (upper left) and [(HO)9(H20)2Eu7(calix[9])2(DMSO)6] (bottom left). Their respective core structures are shown on the right (redrawn after Fleming et al., 2003). 

Figure 2. Effect of temperature on the SFE of Au from cellulose paper at a pressure of 400 atm using synthesised fluorinated tetrameric calixarene ligands (20 mg ligand, 40 pL Au, 30 min static, 15 min dynamic). (Reproduced with permission from reference 29. Copyright 1999)...

Formation of the dimeric capsule 5.55 based on calixarene ligand 40 (reprinted with permission... 

Brindley, G.D. Fox. O.D. Beer, P.D. Ferrocene-appended and bridged calixarene ligands for the electrochemical sensing of trivalent lanthanide ions. J. Chern. Soc., Dalton Trans. 2000, 4354-4359. 

Among the first examples of multivalent calixarene ligands are the tetraloop derivatives 94 designed by Hamilton... 

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