Anion Binding Motifs:  Topicity and Charge in Amidocryptands

Abstract

An expanded amidocryptand with propyl linkages provides multitopic sites for binding anions and water molecules. Upon quaternization of the two bridgehead amines, the molecular shape changes from an inverted Y to that of a bowl, which is filled with water and topped by the anion.

Self assembled macrobicycle and tricycle cages containing pyrrole rings by dynamic covalent chemistry method

“…The bridgehead N1…N6 distance is 10.30 Å , which is smaller than that found in the structure of 3, indicating the deformation of the cage owing to the encapsulation the chloride anions. Similar dihalide anion complexes and cascade like coordination with water bridging have been reported by Bowman-James and co-workers [60][61][62]. Further, the Cl1…Cl2 distance of 3.69 Å is shorter than that (4.433 Å ) reported for the azamacrocycle containing two chloride ions [63].…”

Alfred Werner’s expanded legacy: Anion and metal ion coordination in an unsymmetrical, octaamido cryptand

“…Again this would indicate interaction with all three of the symmetry independent amide hydrogen atoms, as verified by the crystal structure. Association constants obtained were compared with those previously reported for the cryptand C 4 [25,27] (Table 2). Unfortunately, rather than increasing the binding affinity by increasing the size of the cryptand cavity, the opposite effect was observed, although 1 shows very strong binding toward the larger monohydrogen pyrophosphate.…”

“…The rationale for this was their lessened sensitivity to degree of protonation, their solvent preferences (more amenable to mixed solvent separations applications), and last but not least, their analogy with the naturally occurring amide hosts in protein systems [24]. As part of this examination of polyamide hosts, we designed and synthesized the corollary to the aza cryptands, bicyclic polyamide cryptands (with six amide binding sites), C 4 [25][26][27][28]. To our knowledge this new cryptand framework represented only the second example of tren-based amide cryptands, the first being the elegant catechol systems of Raymond and co-workers, used as mimics of the iron-loving siderophores [29][30][31].…”

Anion channel structure through packing of cucurbit[5]uril-Pb2+ or cucurbit[5]uril-Hg2+ complexes

“…The fundamental and practical reasons for this interest have been discussed thoroughly and many host molecules that include anions have been studied [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. Cucurbit[n ¼ 5-8, 10]uril (figure 1), which has a hollow core and identical carbonyl-fringed portals on each side, having a barrel shape, is one kind of fascinating organic macrocyclic cavitand [17][18][19].…”