A biscalix[4]arene-based ditopic hard/soft receptor for K+/Ag+ complexation

Artificial Allosteric Receptors

“…[13,14] A similar approach was presented by Rodríguez-Ubis and Brunet and co-workers who described a strong negatively cooperative allosteric effect in the transport of diammonium ions by receptor 25 in the presence or absence of ZnI 2 as the effector (Scheme 20). [64] Other examples were designed by Lhotµk and Stibor and co-workers (28, Scheme 23) and Nabeshima and co-workers (29 and 30, Scheme 24) to influence the binding of a hard alkali metal ion by interactions of soft silver(I) ions as effectors via cation-p [65] interactions or interactions with soft donor atoms [66,67] or vice versa to achieve heterotropic negatively cooperative behavior. Krämer and co-workers, e. g. observed somewhat surprisingly that binding of zinc(II) or copper(II) ions was disfavoured in his metallated container 26 compared to the similar but positively cooperative ionophores of Katoh and Nabeshima and co-workers 17 and 18 depicted in Scheme 14.…”

“…[107,108] Again the metal ions were used to stabilize cone conformations such as in receptors 40 and 57-59. Here, however, this was employed to either create a concave binding site at all (65) or to adjust its curvature (66) in such a manner that it is complementary to the fullerene guests. Interestingly, different alkali metal ions were found to cause different effects: whereas lithium acts as a positive effector, sodium binding was found to cause a negative allosteric effect.…”

“…Interestingly, however, the selectivity of metallated 27 for potassium ions compared to lithium or sodium ions was strongly enhanced (Scheme 22). [64] Other examples were designed by Lhotµk and Stibor and co-workers (28, Scheme 23) and Nabeshima and co-workers (29 and 30, Scheme 24) to influence the binding of a hard alkali metal ion by interactions of soft silver(I) ions as effectors via cation-p [65] interactions or interactions with soft donor atoms [66,67] or vice versa to achieve heterotropic negatively cooperative behavior.…”

One-step synthesis of a singly bridged biscalix[6]arene and evaluation of its alkali metal recognition properties

“…4,5 For example, biscalixarenes joined via tail-to-tail linkage provide two diverging cavities and have been utilized for the formation of polycaps, 6 as redoxactive ionophores 7 and ditopic receptors 8 etc. Earlier, our research group members have demonstrated the synthesis 9,10 and application [11][12][13][14][15][16] of various calixarenes as hosts in selective complexation with different guests such as cesium ion, 11,12 fullerenes [13][14][15] as well as in transportation of uranyl ion across a liquid membrane.…”

One‐Step Synthesis of Singly Bridged Biscalix[4]arenes with Oligooxyethyleneethyl Spacers

“…[3] They are examples of higherorder molecular architectures with new high-level host properties such as cooperative action [4] and allosteric effects, [5] which give hosts stronger inclusion ability, higher selectivity, and so on. A series of double-calix[4]-arene-bis(crown-3) have been found to exhibit much higher complexation efficiencies for quaternary ammonium cations than those of the corresponding calix[4]arene-bis(crown-3), [6] as did some biscalix[4]arenes toward Hg 2þ , [7] Ag þ , [8] lanthanide ions, [9] and uranyl cation. [10] Biscalix[4]arenes possess two metal binding sites, which can form a stable 1:2 complex with metal cations in solution.…”