A naked-eye selective detection of cyanide ion: studies on the effect of chromophores and spacers on ditopic receptors

Abstract

A series of novel thiourea based receptors (1-12) with different signaling units and spacers have been synthesized for the detection of cyanide ion. Among these receptors, 4,4'-bis-[3-(4-cyanophenyl)thiourea]diphenyl sulfide 6 and 4,4'-bis-[3-(3-cyanophenyl)thiourea]diphenyl sulfide 9 exhibited selective detection of cyanide by the naked-eye as well as by UV-Vis spectroscopy. Furthermore, the chemosensor is insensitive to the presence of other environmentally relevant anions. The chromogenic transformation permits the detection of cyanide (TBA(+) and K(+) salts) in the natural environment.

Synthesis and Photophysical Characterization of Proton Transfer-Based Thiourea Derivatives: Potential Application as Colorimetric Naked-Eye Chemosensor for Fluoride Detection in Solution

“…Finally, at 0.8 equiv., the broad signal shifts downfield another 0.2 ppm, unlike that observed in receptors containing the same chemical grouping, where the signal related to NHs completely disappears. 20 A similar behavior was observed to compound 9. Although the literature shows a relation between the disappearing of hydrogen signals in the 1 H NMR titration with a full proton transfer from the chemosensor to the analyte, 48 some authors also indicate the disappearing of signals from the chemosensor due to hydrogen bonding 6,49 or both.…”

“…Although the literature shows a relation between the disappearing of hydrogen signals in the 1 H NMR titration with a full proton transfer from the chemosensor to the analyte, 48 some authors also indicate the disappearing of signals from the chemosensor due to hydrogen bonding 6,49 or both. 20 There is no clear definition concerning this experiment and the proposed interaction mechanism. In this work, in a general way, it was observed that the thiourea hydrogens shift downfield and remain present during titration, which in our opinion corroborates the HB mechanism in this site of the molecule.…”

“…Different amounts of these solutions were added to DMSO solutions of the compounds 8-9 (10 -6 mol L -1 ). 20 The continuous variation method (Job plot) was obtained from a molar fraction of 0.1-1.0 of chemosensor/fluoride. The absorbance intensity was monitored at 410 and 432 nm for compounds 8 and 9, respectively.…”

“…It should be noted that the reaction of isothiocyanates with aromatic amines is very fast, and there is no need for the use of catalysts. 20 In the 1 H NMR spectrum of compound 8 (see SI section), it is possible to observe a singlet in the region above 11.00 ppm relative to the hydrogen of the phenolic OH. This signal usually appears between 4.00 and 7.50 ppm, but when IHB occurs, a frequency shift is observed for the region between 12.00 and 11.00 ppm.…”

“…[14][15][16][17] In addition, the signaling unit responsible for this interaction must be responsible for the detection of the analyte using the usual spectroscopic techniques, such as UV-Vis absorption or fluorescence emission, or even naked-eye detection, the latter presenting advantages over spectroscopic techniques. [14][15][16][17] According to this particular chemical interaction, different chemosensors involving urea or thiourea groups, [18][19][20] amides, 7 porphyrin 15 and phenols 6,16,17,21 have been described in the literature.…”