Synthesis and evaluation of fluorimetric and colorimetric chemosensors for anions based on (oligo)thienyl-thiosemicarbazones

Carbohydrazone/Thiocarbohydrazone-Based Dual-Responsive Probes for Highly Selective Detection of Cu2+/Fe3+ Cations and F-/ClO4 - Anions, and Their Application in Bioimaging of Live Cells and Zebrafish Larvae

Four dual-responsive probe molecules 1,5-bis(thiophene-2-carbaldehyde)carbohydrazone (R1), 1,5-bis(thiophene-2-carbaldehyde)thiocarbohydrazone (R2), 1,5-bis(indole-3-carbaldehyde)carbohydrazone (R3), and 1,5-bis(indole-3-carbaldehyde)thiocarbohydrazone (R4) were synthesized, characterized, and investigated for their sensing efficacy. The initial sensing behavior of the probes was tested by colorimetric signaling, followed by spectral and theoretical techniques, which supported the dual-sensing ability of the selected inorganic ions. The probes exhibited highly selective optical recognition for Cu2+/Fe3+ cations and F-/ClO4 - anions compared to the tested cations and anions. Interestingly, the addition of Cu2+ and F- ions to the probes resulted in "turn-on" fluorescence responses. Job's plot studies showed 1:2 stoichiometry between the probe molecules and cations and 1:1 stoichiometry between the probe molecules and anions. The binding constant of the probe molecules with the sensed ions was determined by the Benesi-Hildebrand equation and was found to be between 7.08 × 104 and 7.44 × 106 M-1 with a limit of detection between 0.11 and 0.80 μM, in CH3CN:DMF (9:1, v/v). Density functional theory calculations established the nature of the interaction between the probe molecules and sensed ions. Further, the practical utility of the probes was successfully demonstrated with paper strip experiments, fluorescence imaging of Cu2+ ions in DrG cells and zebrafish larvae, as well as in the development of molecular logic gates.

Theoretical study on the sensing mechanism of an ON1-OFF-ON2 type fluoride fluorescent chemosensor

A density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations have been used to study the sensing mechanism of an ON¹-OFF-ON² type fluoride anion fluorescent chemosensor (Bis[[7-(diethylamino)-2-oxo-2H-chromene]methyl-ene]‑carbonothioic dihydrazide (CTC). The current theoretical calculation presents a different sensing mechanism from the experimentally proposed one (Sensor and Actuators B 2016, 222, 823-828). Instead of the combination of CTC deprotonation and poorly emissive excited state tautomer or ICT mechanism, the theoretical results predict the sensing mechanism based on dissociation reaction and excited-state proton transfer (ESPT). The calculated vertical excitation energies both in the ground states and first excited states of different forms of CTC, as well as the potential-energy curves, have completely reproduced the experimental results, providing powerful evidence for our proposed CTC sensing mechanism for fluoride anion.

Detection of cyanide ions in aqueous solutions using cost effective colorimetric sensor

Cyanide (CN̄) is one of the most toxic material to the human and environment. It is very important to develop the diagnostic tools for the detection of CN̄ ions. Moreover, detection of the ions in an aqueous medium is a challenging task as water molecules interfere with the sensing mechanism. In this context, we prepared chemical sensor, S1, having anthraquinone as a signaling unit and thiourea as a binding site. This sensor exhibited distinct visual color and spectral changes in response to CN̄ ion over other testing anions in 50% aq. DMSO solution. However, in 20% aq. DMSO solution, S1 exhibited obvious spectral and color changes in response to CN̄, fluoride (F̄), acetate (Ac̄) and benzoate (Bz̄). Another sensor, S2, having a same signaling unit with that of S1, but a different binding site of urea group. In contrast to S1, S2 exhibited obvious spectral and color changes to F̄ in 2.5% aq. DMSO solution. NMR titration results suggested that the spectral and colorimetric responses were due to the formation of host-guest complex and deprotonation events. Finally, economically viable paper-based colorimetric "test stripes" of S1 were fabricated to detect the CN̄ ions in 100% aqueous solution.

A ruthenium(iii) complex derived from N,N′-bis(salicylidene)ethylenediamine as a chemosensor for the selective recognition of acetate and its interaction with cells for bio-imaging: experimental and theoretical studies

A ruthenium(iii) complex ofN,N′-bis(salicylidene)ethylenediamine (L¹) was used as chemosensor for the recognition of acetate in cells for bio-imaging.

The interaction of Eu(iii) with organoborates – a further approach to understand the complexation in the An/Ln(iii)–borate system

A combination of different spectroscopy techniques, DFT calculations and advanced data analysis explained the Eu(iii)–organoborate complexation.

Formation of a Eu(iii) borate solid species from a weak Eu(iii) borate complex in aqueous solution

Using time-resolved laser-induced fluorescence spectroscopy (TRLFS) the transformation of a dissolved Eu(iii) borate species into a solid Eu(iii) borate was observed.

Synthesis and evaluation of simple naked-eye colorimetric chemosensors for anions based on azo dye-thiosemicarbazones

A series of novel, highly selective azo dye-thiosemicarbazones based anion sensors (3e-f) have been synthesized from the condensation reaction between thiosemicarbazide and six different azo salicylaldehydes. The structure of the sensors was confirmed by spectroscopic methods. The selectivity and sensitivity in the recognition for acetate anion over other anions such as fluoride, chloride, iodide and dihydrogenphosphate anions were determined by naked-eyes and UV-vis spectra. The color of the solution containing sensor had an obvious change from light yellow to orange only after the addition of acetate anion in aqueous solution (water/dimethylsulfoxide, 7:3, v/v) while other anions did not cause obvious color change. The anion recognition property of the receptor via proton-transfer is monitored by UV-vis titration and (1)H NMR spectroscopy. Under condition in aqueous solution of sensor 3e (water/dimethylsulfoxide, 7:3, v/v), linearity range for the quantification of acetate anion was 1-22 μM and limit of detection (LOD) of acetate anion was 0.71 μM.