A dual-response naphthalene-armed calix[4]arene based fluorescence receptor for Zr(IV) and Fe(II) via Ligand to metal charge transfer

A new and dual-response calix[4]arene based fluorescence sensor; 5, 11, 17, 23-tetra t-butyl-25, 26, 27, 28 tetracarboxylate naphthalene calix [4]arene (C4N) has been designed and developed for the recognition of Zr4+ and Fe2+. The fairly linear range of C4N for Zr(4+ )and Fe2+ is 5-205 nM and 5-210 nM respectively. This sensor exhibits favourable selectivity towards Zr(4+ )and Fe2+ with the detection limit of 1.98 nM and 4.05 nM respectively via ligand to metal charge transfer (LMCT). This interesting supramolecular architecture has been exploited by UV-vis spectroscopy, voltammetry, electmspray ionization mass spectroscopy (ESI-MS), powder xray diffraction (PXRD) study and fourier transform infrared spectroscopy (FT-IR). The binding constant of C4N with Zr4+ and Fe2+ is calculated to be 8.139 x 10(8) M-1 and 8.430 x 10(8 )M(-1) respectively. The quantum mechanical study of C4N, C4N: Zr4+ and C4N: Fe2+ has been implemented using Gaussian 09 W software. Hybrid Becke's three parameters exchange functional (B3LYP) level using standard STO-3 G basis set is used to optimize geometry of C4N and its composite metal cations. To strengthen the experimental florescence study, highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) energy band gap for C4N and C4N with Fe2+ and Zr4+ is also carried out, which reveals the enhancement and quenching effect in the luminous study. The molecular docking study has performed different protein receptors of metal-phosphodiesterase proteins (4MCW, 4MDZ, 4ME4, 6NVP and 6NVO) with C4N using HEX software.

Automated summary

A new dual-response calix[4]arene-based fluorescence sensor has been developed for the recognition of Zr4+ and Fe2+, with favorable selectivity and detection limits ranging from 5-205 nM to 5-210 nM. The sensor was characterized using various techniques including UV-vis spectroscopy, mass spectroscopy, and X-ray diffraction, revealing interesting supramolecular structures and binding constants.