Synthesis of novel p-tert-butyl-calix[4]arene derivatives and their cation binding ability: chromogenic effect upon side arms binding

A series of novel double-armed calix[4]arene derivatives, i.e. 5,11,17,23-tetra-tert-butyl -25,27-bis[2-[(2-hydroxy-5-(4-nitroazo)benzylidene)amino]ethoxy]-26,28-dihydroxy-calix[4]-arene (), 5,11,17,23-tetra-tert-butyl-25,27-bis[2-[(2-hydroxy-5-(2-nitroazo)benzylidene) amino]ethoxy]-26,28-dihydroxycalix[4]arene (), 5,11,17,23-tetra-tert-butyl-25,27-bis[2-[(2-hydroxy-5-(4-chloroazo)benzylidene)amino]ethoxy]-26,28-dihydroxycalix[4]arene (), have been synthesized as an selective chromoionophore for Na+. The complexation behavior of ligands with alkali metal ions Na+, K+, Rb+and Cs+ has been evaluated by using UV–Vis spectrometry in CH3CN–H2O (99:1/V:V) solution at 25°C. The UV–Vis spectra show that the complexation of with Na+exhibits obvious bathochromic shifts (λmax 379→480 nm) and there is a unique color change in the solution from yellow to red upon complexation. The binding constants for Na+ are higher than that of other alkali metal ions, giving the highest cation selectivity up to 7 for Na+/K+. The binding ability and photophysical behavior of alkali cations by calix[4]arene derivatives are discussed from the point of view of substituted effects at the lower rim of parent calix[4]arene and size-fit concept between host calix[4]arenes and guest cations.