First Pseudorotaxane-Like [3]Complexes Based on Cryptands and Paraquat:  Self-Assembly and Crystal Structures

Abstract

A new cryptand, bis(1,3,5-phenylene)tri(1,4,7,10-tetraoxadecyl) (3a), has been synthesized in good yield from bis(5-hydroxy-1,3-phenylene)-26-crown-8 (2a) and tri(ethylene glycol) ditosylate using pseudo-high dilution conditions. 3a forms a strong 1:1 complex with paraquat (1) in acetone solution with a high apparent association constant, 1.4 x 10(4) M(-)(1). A stoichiometry of 1:1 was also observed by mass spectrometry in the gaseous state. However, in the solid state, as determined by X-ray crystallography, the two complexes of 3a and the previously reported homologous cryptand, bis(1,3,5-phenylene)tri(1,4,7,10,13-pentaoxatridecyl) (3b), with paraquat (1) have 2:1 stoichiometry. A unique feature of these trimolecular pseudorotaxane-like complexes is that the guest occupies parts of the cavities of two cryptand molecules. For the first time it was found that in cryptand-based complexes, different stoichiometries are possible for the same host-guest pair.

Molecular recognition of organic ammonium ions in solution using synthetic receptors

“…Paraquat and its derivatives are widely used in crown ether rotaxanes and several recent examples of crown ether [197–202] or cryptand [203–205] complexes with paraquat have been described. Such complexes are not within the scope of this review and the interested reader is referred to the literature cited above.…”

A new cryptand/paraquat [2]pseudorotaxane

“…In order to improve complexation with paraquat derivatives, we introduced cryptands that have proved to be much better hosts than simple crown ethers [14][15][16][17][18]. Most of these reported cryptand/paraquat complexes are only pseudorotaxane-like because paraquat is not long enough to extend outside of the cavities of cryptands [14][15][16][17][18]. Here we report a "true" cryptand/paraquat [2]pseudorotaxane in which the paraquat derivative guest is long enough to extend from the cavity of the host.…”

“…Crown ethers [7][8][9][10][11][12][13], cryptands [14][15][16][17][18], cyclodextrins [19][20][21][22], cucurbit[n]urils [23][24][25], and calix[n]arenes [26,27] have been universally used as hosts to fabricate various supramolecular assemblies, which have great potential in molecular devices, chemosensors, and nano materials. Paraquat ( Figure 1) and its derivatives (N,N′-dialkyl-4,4′-bipyridinium salts) are common guests in the field of pseudorotaxanes and rotaxanes [28][29][30][31].…”

“…They have been widely used to construct numerous host-guest complexes with bis(p-phenylene)-34-crown-10 (BPP34C10, 3) derivatives and bis(m-phenylene)-32-crown-10 derivatives (BMP32C10) [28][29][30][31]. In order to improve complexation with paraquat derivatives, we introduced cryptands that have proved to be much better hosts than simple crown ethers [14][15][16][17][18]. Most of these reported cryptand/paraquat complexes are only pseudorotaxane-like because paraquat is not long enough to extend outside of the cavities of cryptands [14][15][16][17][18].…”

Anion‐Assisted Complexation of Paraquat by Cryptands Based on Bis(m‐phenylene)‐[32]crown‐10

“…[11] The crown-ether-based cryptand 1 (Figure 1) has proved to be a powerful host for the paraquat salt 2 a. [3a] According to the X-ray structure of the complex 1·2 a, the bipyridinium dicationic part threads into the cavity of the crown-ether-based cryptand 1 with the assistance from two hydrogen bonds formed between the two acidic b-pyridinium hydrogen atoms and the oxygen atom of a water molecule that bridges to the ether oxygen atoms of the third ethylenoxy chain.…”