Synthesis and evaluation of novel 1,3-bridged calix[4]arene-crown ethers for selective interaction with Na+/K+ cations

Calix4]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 calix4]arene-crown ethers 2a–2h, in good yields. The binding properties of the synthesized 1,3-bridged calix4]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 calix4]arene-crown ether. The potassium/sodium selectivity seems to be governed primarily by the size of the crown ring, relative hydrophobicity and cation-π interaction capability to give efficiency order as 2a, 2d?>?2?h?>?2c, 2e?>?2b, 2f?>?2?g.