Spectroscopic behavior on the formation complex of three double-armed calix[4]arene derivatives with lanthanoid nitrates in acetonitrile

Abstract

The complexation spectroscopic behavior of three p- tert-butylcalix[4]arene Schiff bases i.e. 5,11,17,23-tetra- tert-butyl-25,27-bis[2-[ N-(3-nitrobenzylidene)amino]ethoxy]-26,28-dihydroxycalix[4]arene ( 1), 5,11,17,23-tetra- tert-butyl-25,27-bis[2-[ N-(2-hydroxybenzylidene)amino]ethoxy]-26,28-dihydroxycalix[4]arene ( 2), and 5,11,17,23-tetra- tert-butyl-25,27-bis[2-[ N-(2-hydroxy-3-methoxybenzylidene)amino]ethoxy]-26,28-dihydroxycalix[4]arene ( 3) with lanthanoid nitrates (Tb 3+ and Eu 3+) has been investigated in anhydrous acetonitrile at 25 °C by using UV–vis and FT-IR as well as fluorescence spectra. The results obtained indicated that the spectroscopic behavior of compounds 1– 2 upon complexation with lanthanoid ions did not show any significant larger difference in comparison with free compounds 1 and 2, which may be contributed to the poor binding ability. Contrary to compounds 1 and 2, the lower rim functional groups in compound 3 can form two large π electron conjugate system with lanthanide ion and encapsulate lanthanide ions tightly, displaying the novel spectroscopic behavior upon complexation with lanthanide ions. As compared with compound 3, the formation complexes of compound 3 with Tb 3+ and Eu 3+ showed new broad intense absorption at 398 nm, respectively, and IR spectra showed that OH stretching vibration at 3413.40 cm −1 displayed a large drop. It is interestingly noted that the narrow emission line spectra were observed only for 3 complex with Tb 3+, but did not for 3-Eu 3+complex. In the 3-Eu 3+ complex, the broad-band emission at λ max=534 nm was obtained at the excitation of 398 nm. The spectroscopic behavior of three calix[4]arene derivatives upon complexation with lanthanoids was discussed from the relationship between the host structure and the properties of guest lanthanide ions.