Synthesis of Unique Ionophores of Penta-Crown Ethers

Abstract

Structurally unique novel ionophores of penta-crown ethers were successfully synthesized. Diaza-18-crown-6 was designed as the parent crown ring. The penta-crown ethers were prepared by the reaction of 1,3,5-triacryloylhexahydro-1,3,5-triazine (TAHTA) with diaza 18-crown-6 followed by a Michael reaction. The binding interactions of the newly synthesized penta-crown ethers with alkali metal cations were examined; the results indicate that the new penta-crown ethers can bind alkali cations of different sizes.Crown ethers have attracted significant attention from various fields since they were first introduced by Pedersen in 1967. 1 During the last two decades, considerable research interest has been devoted to the design of multisite crown ethers, in particular the construction of multisite molecular receptor molecules capable of binding two or more guest metal cations. [2][3][4][5] The crown ether moiety is one of the most popular host compounds in host-guest chemistry field, which has shown a remarkable ability to form strong complexes with alkali metal, alkaline metal, and organic cations. Metal cations exactly fitting the size of the crown ether unit form a host/guest 1:1 complex; when the cation size exceeds that of the crown cavity the cation can only partially fit and, as a result, can be accommodated by two crowns forming a host/guest 2:1 sandwich complex, 6-14 such as the 'butterfly crown ethers'. [11][12][13][14] The 'bis-crown effect' occurs when two crown ether rings in one molecule bind a cation in a sandwich-type structure; it enables the molecules to bind a cation that is larger than the ideal size for particular crown ether unit. [15][16][17][18][19] This is due to the bridge effect of the metal cations with the two crown rings. The formation of sandwich complexes is strongly favored when the crowns are linked by a spacer. In this case, the selectivity towards large cations is increased. 8,10,20 The 'bis-crown effect' can be applied to synthetic methodology and medical chemistry when constructing new organic and inorganic molecular receptors.We reported 21,22 the synthesis of unique structural trisand tetra-crown ethers, novel host compounds which contain multisite crown rings are of great interest, they can form host/guest 1:n (n ≥ 3) complexes. Herein, we report the design, synthesis, and characterization of a new type of ionophores of penta-crown ethers. The structures of the newly synthesized penta-crown ethers are outlined in Figure 1. To our knowledge, there have been few reports of compounds containing five crown ether rings. The binding interactions of the penta-crown ethers with alkali metal cations were examined. From the results, we found that the newly synthesized ionophores of penta-crown ethers had the ability to complex with alkali metal cations of various sizes such as Na + , K + , and Cs + . The new pentacrown ionophores lead to original applications for the preparation of new types of host-guest complexes. The properties can be applied in different areas, such as synthetic, medicin...

Crown ether-based structures for sensitive electrochemical detection

“…4 Different crown ether-based structures have been exploited for constructing chemically modified electrodes, which offer the possibility of selective complexation of a cation. [5][6][7][8] In a previous article, 9 we reported the application of a siloxane-crown ether polyamide in the electrochemical detection of lead (Pb) at parts per billion (ppb) levels.…”

“…The crown ethers and their applications have been widely described in the literature [1][2][3] due to their remarkable ability to form strong complexes with metal and organic cations. 4 Different crown ether-based structures have been exploited for constructing chemically modified electrodes, which offer the possibility of selective complexation of a cation. [5][6][7][8] In a previous article, 9 we reported the application of a siloxane-crown ether polyamide in the electrochemical detection of lead (Pb) at parts per billion (ppb) levels.…”

Synthesis and Crystal Structure Determination of [H2‐cryptand 222](Br3)2: A Unique Tribromide Catalyst for the Catalytic Chemoselective N‐Boc Protection of Amines

“…N-Boc pro- 2 In a round-bottomed flask (100 mL) equipped with a magnetic stirrer, bromine (0.494 g, 3.1 mmol) was added to a solution of cryptand 222 (0.376 g, 1 mmol) in ethanol (30 mL) and the mixture was stirred for 0.5 hour. Filtration through a sintered glass funnel gave a fine yellow powder [0.81 g, 95% yield], which was recrystallized from CH 3 The solution was stirred at room temperature for one minute.…”

“…Crown ether moieties are popular host compounds in host-guest chemistry and these ligands have shown a remarkable ability to form strong complexes with organic and inorganic cations [1][2][3] or anions, 4,5 selectively. Among the crown ethers, cryptand 222, a macrobicyclic compound, has been used in a variety of applications including the formation of a conductometric mercury [II] sensor based on poly aniline, 6 the encapsulation of alkali metals, especially K + , [7][8][9] use as an acceptor ligand for the formation of complexes containing 7,7,8,8-tetracyanoquinodimethane (TCNQ), 10 extraction of uranium(VI), 11 exchanging the cations of micas 12 and extraction of copper(II) with erythrosine B.…”

{[[K.18-Crown-6]Br3}n: A tribromide catalyst for the catalytic protection of amines and alcohols

“…Crown ethers have attracted significant attention in various fields of science. Crown ether moieties are popular host compounds in host-guest chemistry, and these ligands have a remarkable ability to selectively form strong complexes with organic and inorganic cations [1][2][3] and anions [4,5]. Among the crown ethers, the 18-crown-6 forms a very stable complex with K + , and it has the maximum stability constant among alkali complexes with metal cations [6,7].…”