Switching the Ion Selectivity from Fe~(3+) to Al~(3+) by a Triazole-Appended Calix[4]arene-Based Amphiphile

摘要

A triazole appended benzaldehydic lower rim derivative of calix [4]arene (L) has been synthesized and was thoroughly characterized. In CH3CN solution, the L showed greater sensitivity for Fe3+ by a 5-fold increase in the absorbance and 37% quenching in the fluorescence intensity, by forming a 1:1 complex. The Fe3+ induces aggregation in L as studied by microscopy. The Langmuir film formed at the air-water interface was characterized by pressure-area isotherm and Brewster angle micrographs, both in the presence and absence of metal ions. The Langmuir films of pure L, {L+Al~(3+)} and {L+Zn~(2+)} were transferred onto H-terminated Si-wafer and characterized using Atomic Force Microscopy, contact angle, Grazing Incidence Fourier Transform Infrared Spectrscopy and X-ray Photoelectron Spectroscopy. The study resulted selective binding of Al~(3+) to the Langmuir film of L among the nine metal ions studied. Thus, the calix[4]arene-conjugate L is sensitive and selective to Fe~(3+) in acetonitrile solution whereas to Al~(3+) in Langmuir film and hence acts as an ion switch depending upon the physical state of L.