Ratiometric Fluoride Research Articles

Synthesis of fluorescent, ortho-azonaphthol-containing conjugated polymer for ratiometric fluoride ion sensing

A conjugated polymer containing the ortho-azonaphthol (o-AN) group was synthesized via the Suzuki coupling reaction, exhibiting an orange color and red fluorescence in its solution. Because the o-AN group contained an OH group adjacent to the azo group, it had an intramolecular H bond, providing backbone planarity. The H bond could be altered by exposure to F ions, showing an intense color change. The o-AN unit in the main chain of the polymer played an important role in F-ion detection and the resultant ratiometric color change. The o-AN monomer was not fluorescent in solution, but the o-AN-containing polymer did fluoresce in its solution, enabling ratiometric fluorescence color change from red to blue. The deprotonation of the OH group in the polymer, abstracted by F ions, enabled chromic and fluorogenic detection with suitable limits of detection of 0.96 and 2.55 μM, respectively, for drinking water.

A novel colorimetric and ratiometric fluoride ion sensor derived from gallic acid

We report a novel colorimetric and ratiometric fluoride ion sensor derived from gallic acid.

A simple colorimetric and ratiometric fluoride ion probe with large color change.

Two colorimetric and ratiometric fluoride ion probes SHJ-1 and SHJ-2 based on the acylhydrazone skeleton have been developed. Among the eight anions (F−, Cl−, Br−, I−, ClO4−, H2PO4−, HSO4−, CH3COO−), the present probes showed high selectivity and sensitivity toward fluoride ion detection with obvious color change. Notably, the probe SHJ-1 exhibited a red shift of 145 nm upon fluoride sensing, which is the largest value among fluoride ion probes based on acylhydrazone derivates to date. 1HNMR titration study and theoretical calculations suggested that the strong binding of the probe SHJ-1 to fluoride as well as the further deprotonation may facilitate the intramolecular charge transfer transition. These two probes are 1 : 1 complexed with fluoride ions, and the detection limits were calculated to be 1.24 μM for SHJ-1 and 15.73 μM for SHJ-2.

The mechanism of ratiometric fluoride sensing and the ESIPT process for 2,6-dibenzothiazolylphenol and its derivative

In this work, we explore the excited state intramolecular proton transfer (ESIPT) process and the relevant fluoride-sensing mechanism of two novel chemical systems, 2,6-dibenzothiazolylphenol (26DB) and bis-2,6-dibenzothiazolylphenol (Bis-26DB).

A selective ratiometric fluoride ion sensor with a (2,4-dinitrophenyl)hydrazine derivative of bis(indolyl) methane and its mode of interaction

An easy-to-synthesis chemosensor was synthesized and employed as a selective optical chemosensor for fluoride through naked eye detection, which allow us to detect and estimate the concentration of fluoride ion accurately up to 2 μMviaratiometric responses.

2-Hydroxyarylimidazole-based colorimetric and ratiometric fluoride ion sensors

Two novel 2-hydroxyarylimidazoles were developed as colorimetric and ratiometric sensors for the naked-eye detection of fluoride anions. The discriminating absorption and fluorescence responses to fluoride in acetonitrile as well as a methanol–acetonitrile solvent system were observed. The bathochromic optical changes are attributed to the deprotonated species evidenced from 1H NMR titrations. Their selectivity for fluoride over acetate was successfully established in the methanol–acetonitrile mixture. A fluorene-bridged imidazole dimer, 4a demonstrated better response for fluoride than acetate in the neat acetonitrile. Moreover, the sensor 4a exhibited a larger ratio of fluorescence intensity response (I489/I431 = 51) than 4b (I521/I448 = 18) for fluoride in acetonitrile.

Analyzing excited-state processes and optical signatures of a ratiomeric fluorine anion sensor: a quantum look

Recently, the spectroscopic signatures of a benzoselenadiazole derivative have been investigated in the framework of designing a new ratiometric fluoride sensor (Saravanan et al., Org Lett, 2014, 16: 354–357). It was suggested that this sensor is undergoing excited-state intramolecular proton transfer. In this work, we provide a new look at these experimental data, using a state-of-the-art time-dependent density functional theory approach to mimic the spectroscopic signatures. New insights about the nature of the excited-state processes are obtained.

A newly developed highly selective ratiometric fluoride ion sensor: Spectroscopic, NMR and density functional studies

A new easy-to-synthesize chemosensor, 3,3'-bis(indolyl)-4-chlorophenylmethane (hereafter S), was designed, synthesized and employed as a selective optical chemosensor for fluoride ions.(1)H NMR and density functional studies on the system have been carried out to determine the nature of the interaction between S and X(-) (X = inorganic anions) responsible for the significant fluoride-induced changes in the absorption properties of S. The experimental results reveal that abstraction of an acidic proton of S by the fluoride ion, leading to the formation of anionic species, is responsible for the spectral changes. These changes allow signaling for the fluoride ion to detect and estimate the concentration of fluoride ion present even at the submicromolar level, accurate up to 2 μM. Calculations of the transition energies of S, S(-), and S···F(-) (hydrogen bonded complex) show that only S(-) is responsible for the long-wavelength absorption band in the presence of F(-).

Through-Space Charge-Transfer Emitting Biphenyls Containing a Boryl and an Amino Group at the o,o′-Positions

A new class of organoboron compounds containing a boryl and an amino group at the o,o'-positions of biphenyls display bright through-space intramolecular charge transfer fluorescence owing to the close contact between the boryl and the amino groups. Binding of the fluoride ions results in the remarkable blue shift and color change of the fluorescence, enabling colorimetric and ratiometric fluoride ion sensing.

Norharmane: Old yet highly selective dual channel ratiometric fluoride and hydrogen sulfate ion sensor

Norharmane provides a simple unexplored class of anion receptor, that allows for the ratiometric selective detection of F(-) and HSO(4)(-) ions. The presence of a strong base can easily form hydrogen bonds with the acidic hydrogen bond donor moiety and the relatively strong acid can easily protonate the basic hydrogen bond acceptor moiety, which can modulate the optical response and can detect the anions efficiently with high selectivity. In view of that, it is promising to conceive the use of these systems in various sensing applications as well as in other situations, such as anion transport and purification, where the availability of cheap and easy-to-make anion receptors, would be advantageous.

Cationic Iridium(III) Complex Containing both Triarylboron and Carbazole Moieties as a Ratiometric Fluoride Probe That Utilizes a Switchable Triplet–Singlet Emission

A novel cationic Ir(III) complex [Ir(Bpq)(2)(CzbpyCz)]PF(6) (Bpq=2-[4-(dimesitylboryl)phenyl]quinoline, CzbpyCz = 5,5'-bis(9-hexyl-9H-carbazol-3-yl)-2,2'-bipyridine) containing both triarylboron and carbazole moieties was synthesized. The excited-state properties of [Ir(Bpq)(2)(CzbpyCz)]PF(6) were investigated through UV/Vis absorption and photoluminescence spectroscopy and molecular-orbital calculations. This complex displayed highly efficient orange-red phosphorescent emission with an emission peak of 583 nm and quantum efficiency of Phi=0.30 in dichloromethane at room temperature. The binding of fluoride ions to [Ir(Bpq)(2)(CzbpyCz)]PF(6) can quench the phosphorescent emission from the Ir(III) complex and enhance the fluorescent emission from the N--N ligand, which corresponds to a visual change in the emission from orange-red to blue. Thus, both colorimetric and ratiometric fluoride sensing can be realized. Interestingly, an unusual intense absorption band in the visible region was observed. And the detection of F(-) ions can also be carried out with visible light as the excitation wavelength. More importantly, the linear response of the probe absorbance change at lambda=351 nm versus the concentration of F(-) ions allows efficient and accurate quantification of F(-) ions in the range 0-50 microM.

A Phosphorescent Ir(III) Complex for Selective Fluoride Ion Sensing with a High Signal‐to‐Noise Ratio

A highly phosphorescent Ir(III) complex, containing a dimesitylboryl group in its coordinative phenylpyridine ligand, exhibited a phosphorescence colorimetric and ratiometric fluoride ion-selective sensing behavior and enabled facile signal purification through time-gated acquisition. Poly(methylmethacrylate) films doped with the Ir(III) complex were used to successfully detect fluoride ion in aqueous media.

An Axial Subphthalocyanine as Ratiometric Fluoride Ion Sensor

Abstract A subphthalocyanine derivative (SubPc 1) with a naphthalimide fluorophore at the axial position was designed and synthesized for fluoride ion selective and sensitive sensing. The obvious changes in UV–vis and fluorescence spectra could be observed by naked eyes.