Optical Determination of Thallium(I) and Cesium(I) with a Fluorogenic Calix[4]arenebis(crown-6 ether) Containing One Pendent Dansyl Group

Abstract

A fluorogenic derivative of 1,3-alternate calix[4]arenebis(crown-6) (1) containing a dansyl group in the proton-ionizable side arm has been employed in selective sensing of Tl+ and Cs+ at low concentration levels in MeCN-H2O (1:1) mixed solvent. Optical recognition of these two metal cations by 1 occurs in contrasting modes. On the basis of the results of fluorescence, matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS), and 1H NMR studies, Tl+ and Cs+ react with 1 via formation of 1:1 complexes that differ in coordination arrangement around the metal ion.

Organic‐Inorganic Molecular Nano‐Sensors: A Bis‐Dansylated Tweezer‐Like Fluoroionophore Integrating a Polyoxometalate Core

“…[21,22] The 1 H and 13 C NMR spectra were also consistent with the expected covalent conjugate and, in particular, the signals of the aromatic carbons of 3 are sensibly deshielded (115-153 ppm), with respect to the dansyl chloride precursor (115-135 ppm), the α methylene protons resonate at δ = 2.84 ppm (Δδ = -0.7 ppm with respect to dansyl-free 2), and the amidic (SO 2 NH) proton resonates at δ = 5.95 ppm, which is a chemical shift close to that obtained for the reference derivative 1 in the same solvent (δ =5.82 ppm). [28] The UV/Vis spectrum of 3 (Ͼ200 nm) displays a shoulder at 218 and a maximum at 250 nm, together with a broad absorbance tail extending up to 450 nm.…”

“…The dansyl label carries some key optical properties, such as: (i) intense fluorescence in the visible region; (ii) relatively long emission wavelength; (iii) a high Stokes shift behavior preventing self quenching; (iii) solvatochromism, by effect of a twisted intramolecular charge-transfer (TICT) excited state, and (iv) selective excitation/absorption response of the protonated state, leading to antenna-effects in polydansylated arrays. [16,17] These unique features have been successfully exploited for the molecular design of fluorescent chemosensors in which the dansyl chromophore is used in combination with receptor domains, including multi-dentate ligands, [18] supramolecular hosts such as calix [4]arenes, [19] cyclodextrins, [20] crown ethers, [21] and also nano-silica surfaces. [22] Depending on the dansyl environment, selective fluoroionophores have been obtained with interesting sensitivity towards ions such as Pb 2+ , [23] Hg 2+ , [18,24] and Cu 2+ .…”

Dansyl-containing fluorogenic calixarenes as optical chemosensors of hazardous metal ions: a mini-review

“…At the time of publication, 8 exemplified the first calixarene-based fluorogenic reagent for selective optical sensing of Tl þ . No surprise that under otherwise different conditions of pH, in a contrasting fashion, 8 was found capable of recognising Cs þ as well (58). Favouring of both of these metal ions by the ligand was explained in part by their tendency for cation -p interactions offered by the calix [4]arene framework in 1,3-alternate conformation.…”

Sensing hazardous metal ions using a fluoroionophore calix[4]arene species containing two 8-oxyquinoline groups

“…In particular, it has been reported that spectrofluorimetry using fluorescent probes exhibits many advantages in terms of sensitivity and selectivity in the detection of metal ions such as Cr(VI), 9 Tl(I), and Cs(I). 10 To extend the use of calix [4]arenes as fluorescent probes, we have successfully attached hydroxyquinoline groups to lower rim positions leading to species 1 (5,11,17,23-tetra(tertbutyl)-25,27-bis[(quinoline-8-oxy)propyloxy]-26,28-dihydroxycalix [4]arene) 11,12 (Fig. 1).…”