Synthesis and Metal Ion Complexation Studies of Proton-Ionizable Calix[4]azacrown Ethers in the 1,3-Alternate Conformation

Abstract

A series of novel N-chromogenic calix[4]arene azacrown ethers were synthesized as selective extractants of potassium ion. 1,3-Alternate calix[4]arene azacrown ethers were prepared by reacting 25,27-dipropyloxy-26,28-bis(5-chloro-3-oxapentyloxy) calix[4]arenes with p-toluenesulfonamide in the presence of potassium carbonate. The coupling reaction of calix[4]arene azacrown ether with 2-hydroxy-5-nitrobenzyl bromide in the presence of triethylamine in THF gave the chromogenic calix[4]arene azacrown ether in moderate yield. These compounds show high potassium selectivity over other metal ions as shown by two-phase extraction, bulk liquid membrane, and 1H NMR studies on a ligand-metal complex. It is assumed that the OH of the chromogenic group attached on nitrogen can assist the complexation by encapsulation of the metal.

Synthesis, Characterization and Cation-Induced Isomerization of Photochromic Calix[4](aza)crown-Indolospiropyran Conjugates

“…Several calix [4] and/or divalent cations (alkaline earth-and transition metal ions) depending on the nature of the chromo/fluorogenic pendant side arms [18,19]. The indoaniline counterpart 3a (Fig.…”

“…The respective 1,3-alt 6a,c was prepared following literature method [18]. After detosylation effected by LiAlH 4 , deprotected azacrowns 5a-c and 7a,c were obtained which were then condensed with chloromethylspirobenzopyran 8 [9,11] according to literature analogy to give photochromic molecules 1 and 2 (Scheme 1).…”

Synthesis of a New Calix[4]crown-5-azacrown-5 Dimeric Nano-tube

“…3 More recently, we have reported that a dimeric structure was obtained by reacting 1,3-dipropyl calix [4]arene with N-tosyl tetraethylene glycol dimesylate under basic conditions. 4 Nano-tubes consisting of two [5][6][7] or three 5 calix [4]arene units in the 1,3-alternate conformation were also constructed by linkages at the para position instead of at the phenolic oxygen atoms. We also reported the syntheses of crown ether-capped multimeric calix [4]tubes composed of two, three, four and five 1,3-alternate calix subunits which are linked to each other by diethylene glycol spacers and their binding properties toward metal ions.…”

Proton-diionizable Bis-calix[4]azacrown Ether through Mannich Reaction

“…6 Recently, we have been intrigued by the synthesis of ditopic receptor that is defined with bis-calixazacrown molecule capable of binding two guest ions in the azacrown cavity. [7][8][9][10] For this system we have also tried to synthesize the methoxymethylated compound on the nitrogen atom of the calixazacrown as a precursor of the Mannich product, but the reaction was not accomplished. Interestingly, we then finally found one-pot synthetic method for 2 and 3 as shown in Scheme 1.…”

“…Our synthesis began with 25,27-bis-(1-propyloxy)calix [4]azacrown-5 (1) which was prepared by following our previous report. 7 Under the nitrogen atmosphere, treatment of 1 with paraformaldehyde and 1,4-hydroquinone in benzene led to 1,3-alternate mono-2 and disubstituted 3 with 2 : 8 ratio calculated by the NMR integration. We obtained 2 and 3 with 8% and 55%, respectively.…”