Transition Metal Ion Directed Supramolecular Assembly of One- and Two-Dimensional Polyrotaxanes Incorporating Cucurbituril

Supramolecular chemistry of cucurbiturils

“…The reactions of pseudorotaxanes of the PR44 (n = 4, m = 4) and PR43 (n = 4, m = 3) types with aqueous solutions of cobalt(II) nitrates 47 and nickel(II) nitrates 48 afforded chain polymers. In these polymers, pseudorotaxanes can be in either the trans or cis positions at the octahedrally coordinated metal atoms to form linear chains (PR44) (see Fig.…”

“…51) and Cd(NO 3 ) 2 (see Ref. 47) with pseudorotaxane PR53 in which the organic molecule encapsulated in cucurbituril contains five methylene groups and the meta-substituted terminal pyridine rings. Two silver ions and two pseudorotaxanes coordinated to these ions comprise one turn of the helix (see Fig.…”

“…2, structure F). 47 The networks are packed in layers (the distance between the layers is 12.7 # A). In this case, the catenane structure is not formed.…”

“…A compound prepared by the reaction of the pseudorotaxane PR43 with copper nitrate Cu(NO 3 ) 2 has an analogous layered structure. 47 The cis-coordination of pseudorotaxanes to the metal atoms in a planar-square coordination makes it possible to prepare the so-called molecular necklaces in which several cyclic molecules are threaded onto a larger-size ring. Thus, the coordination of the ethylenediamine ligand in the [Pt(en)(NO 3 ) 2 ] complex (en is ethylenediamine) is such that pseudorotaxanes can occupy only cis positions on reaction with this complex to give nanocycles with three (PR44) (see Fig.…”

Cucurbiturilas

“…Geralmente procede-se, com o CB [6], a cicloadições dipolares com grupos dinitrofenila e à formação de amidas, entre outras, para criar grupo bloqueantes em pseudo-rotaxanos. Alguns grupos bloqueadores são complexos metálicos, que são ligados aos eixos dos rotaxanos, quando estes possuem pontos de coordenação [86][87][88][89][90][91][92][93][94] . É possível criar estruturas do tipo colar de pérolas [95][96][97] , montando polirotaxanos a partir de oligômeros de poliacrilamidas e poliestirenos, além de estruturas tridimensionais como dendrímeros 83,98,99 .…”