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

Abstract

Abstract 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 Zr4+ and Fe2+ is 5−205 nM and 5–210 nM respectively. This sensor exhibits favourable selectivity towards Zr4+ 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, electrospray ionization mass spectroscopy (ESI-MS), powder x-ray 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 × 108 M−1 and 8.430 × 108 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.