877993-13-0Relevant academic research and scientific papers
Synthesis of oligophenylene-substituted calix[4]crown-4s and their silver(I) ion-induced nanocones formation
Wong, Man Shing,Xia, Ping Fang,Lo, Pik Kwan,Sun, Xiao Hua,Wong, Wai Yeung,Shuang, Shaomin
, p. 940 - 946 (2006)
A novel series of oligophenylene OPP(n)-substituted calix[4]crown-4s bearing up to three phenylene units, 1a-d, has been efficiently synthesized by means of either microwave-assisted or silver(I) ion-assisted Pd-catalyzed Suzuki cross-coupling of tetraiodocalix[4]crown-4 and the corresponding oligophenylboronic acids. Complexation of OPP(n)-substituted calix[4]crown-4s with silver (I) ion was substantiated by 1H NMR spectroscopic and high-resolution ESI- or MALDI-TOF- MS studies. The weak binding affinities of OPP(n)-substituted calix[4]crown-4s for silver (I) ion, which were estimated from 1H NMR titrations with binding association in the range of 30-90 M-1, allows reversible disassembling in the presence of KI at ambient temperature. Remarkably, the single-crystal X-ray structures of OPP(n)-calix[4]crown-4-Ag+ complexes indicate the atypical silver (I) ion-crown ether binding mode resulting in the formation of rigid nanocones with volume created up to ～1500 A3. Our results suggested that despite the weak binding affinity of crown ether ligands for silver (I) ion, this weak interaction is still be useful as a tool to construct supramolecular architectures.
Synthesis and evaluation of novel 1, 3-bridged calix[4]arene-crown ethers for selective interaction with Na+/K+ cations
Chawla, Har Mohindra,Hundal, Geeta,Kumar,Singh, Parminder
experimental part, p. 323 - 330 (2012/09/22)
Calix[4]arenes possessing electron-donating groups (OH and OR) at the lower rim when reacted with tosylated polyethers under basic conditions give the corresponding 1, 3-disubstituted calix[4]arene-crown ethers 2a-2h, in good yields. The binding properties of the synthesized 1, 3-bridged calix[4]arene-crown ethers for alkali metal cations have been investigated by atomic emission spectrometric analysis. It has been observed that recognition of sodium and potassium varies with the size of the polyether chain as well as the substituents on the free phenolics of the calix[4]arene-crown ether. The potassium/ sodium selectivity seems to be governed primarily by the size of the crown ring, relative hydrophobicity and cation-pinteraction capability to give efficiency order as 2a, 2d>2 h>2c, 2e>2b, 2f>2 g.
