Colorimetric Recognition of Anions Using Preorganized Tetra-Amidourea Derived Calix[4]arene Sensors

Abstract

The synthesis and the spectroscopic studies of the amidourea based calix[4]arene sensors 1 and 2 are described. The 4-nitrophenyl based sensor 1 was synthesized in two steps from the corresponding calix [4]arene tetraethyl ester and shown to give rise to color changes in the UV-vis spectra in DMSO upon recognition of pyrophosphate and fluoride. Fitting the changes in the absorption spectra using nonlinear regression analysis indicated strong binding of several anions by 1 such as acetate and hydrogen phosphate in 1:1 (Host:Guest) stoichiometry, and at higher concentration in 1:2 stoichiometry. The preorganized calix-cavity was, however, not found to host chlorine while binding of bromide was determined. At high concentrations of these anions, significant colorimetric changes were also observed that were clearly visible to the naked eye for both pyrophosphate and fluoride. The phenyl analogue 2 was made to enable analysis of the anion recognition using 1H NMR titrations and showed that ions such as phosphate were bound in 1:1 stoichiometry, whereas the "urea" protons were shown to be significantly affected upon coordination to the anion.

Stable and sensitive probes for lysosomes: Cell‐penetrating fluorescent calix[4]arenes accumulate in acidic vesicles

“…In particular the ability of derivatives to complex anions (2,3) and cations (4,5) has been exploited for the development of sensors. Recently, interest has focused on the use of calixarene derivatives in biological systems be it as drugs, drug delivery systems, or imaging agents.…”

A Metal–Organic Framework Based on a Tetra-Arylextended Calix[4]pyrrole Ligand: Structure Control through the Covalent Connectivity of the Linker

“…19 The first study, reported by Zhang et al,20 described two 3-D framework constructed from tetra-psulfonatocalix [4]arenes and rare earth cations (i.e. Nd III and Eu III ).…”

Fluorescent asymmetric bis-ureas for pyrophosphate recognition in pure water

“…14 Many different strategies have been developed for designing fluorescent chemosensors for Ppi including the use of charged receptors, 15,16 metal complexes, [17][18][19][20][21] or neutral receptors in particular urea or thiourea receptors. 15,[22][23][24][25][26] We have recently described a new family of symmetric bis-urea receptors which showed a remarkable affinity for Ppi and were able to act as a fluorimetric chemosensors for this anion, even at naked eye. 27 In particular we demonstrated that the presence of naphtyl groups as pendant arms of the ureas, facilitates the binding and the optical fluorimetric selectivity thanks to the uncommon interaction of an aromatic CH from the fluorophore with the Ppi guest.…”