Colorimetric probes based on anthraimidazolediones for selective sensing of fluoride and cyanide ion via intramolecular charge transfer

Probes based on anthra[1,2-d]imidazole-6,11-dione were designed and synthesized for selective ion sensing. Each probe acted as strong colorimetric sensors for fluoride and cyanide ions and exhibited intramolecular charge transfer (ICT) band, which showed significant red-shifts after addition of either the F(-) or CN(-) ion. One of the probes (2) showed selective colorimetric sensing for both cyanide and fluoride ions. In organic medium, 2 showed selective color change with fluoride and cyanide, whereas in aqueous organic medium it showed a ratiometric response selectively for cyanide ion.     

Multi-step detection of cyanide ion by a bis(dimesitylboryl)dibenzoazaborine

A bis(dimesitylboryl)dibenzoazaborine formed Lewis acid-base type complexes with up to two cyanide ions in stepwise fashion. The complex formation constants for cyanide ion were larger than those for fluoride ion, despite the higher affinity of fluoride ion to boron atoms than that of cyanide ion.     

Ammonium boranes for the selective complexation of cyanide or fluoride ions in water

With the recognition of aqueous fluoride and cyanide ions as an objective, we have investigated the anion binding properties of two isomeric ammonium boranes, namely [p-(Mes2B)C6H4(NMe3)]+ ([1]+) and [o-(Mes2B)C6H4(NMe3)]+ ([2]+). These cationic boranes, which could be obtained by reaction of the known 4- and 2-dimesitylboryl-N,N-dimethylaniline with MeOTf, have been investigated both experimentally and computationally. They both react with fluoride and cyanide ions in organic solvents to afford the corresponding fluoroborate/ or cyanoborate/ammonium zwitterions 1F, 1CN, 2F, and 2CN. In aqueous solution, however, these cationic boranes behave as remarkably selective receptors. Indeed, [1]+ only complexes cyanide ions while [2]+ only complexes fluoride ions. In H2O/DMSO 60:40 vol (HEPES 6 mM, pH 7), the cyanide binding constant of [1]+ and the fluoride binding constant of [2]+ are respectively equal to 3.9 (+/-0.1) x 108 and 910 (+/-50) M-1. Structural and computational studies indicate that both steric and electronic effects contribute to the unusual selectivity displayed by these cationic boranes. Owing to favorable Coulombic effects, the para-derivative [1]+ has a very high affinity for cyanide; yet these effects are not sufficiently intense to allow complexation of the more efficiently hydrated and less basic fluoride anion. In the case of the ortho-derivative [2]+, the proximity of the ammonium moiety leads to an increase in the Lewis acidity of the boron center thus making fluoride binding possible. However, steric effects prevent cyanide coordination to the boron center of [2]+. Finally, cation [1]+ and [2]+ bind their dedicated anions reversibly and show a negligible response in the presence of other common anions including Cl-, Br-, I-, NO3-, OAc-, H2PO4-, and HSO4-.     

Anion sensing properties of new colorimetric chemosensors based on macrocyclic ligands bearing three nitrophenylurea groups

Two new colorimetric ligands (1-2) based on macrocyclic structures linked to three nitrophenylurea groups were synthesized in good yields, and their responses toward anions were studied. Anions with different shape, such as of fluoride, chloride, bromide, iodide, hydroxide, nitrate, perclhorate, cyanide, or dihydrogen phosphate in DMSO solution were added and only fluoride, hydroxide, cyanide, and dihydrogen phosphate enhances π delocalization and shifts the π-π^∗ transition in both ligands, leading to the generation of a pleasant orange color.The result is a balance between the acidity of the nitrophenylurea-NH donors modulated by the basic character of the anions. Stability constants for both receptors and the anions fluoride, hydroxide, cyanide, and dihydrogen phosphate were determined spectrophotometrically using the program HYSPEC. ¹H NMR titrations experiments with fluoride were carried out.     

An investigation of the deprotonation of hydrazone-based receptors on interaction with anion: develop a colorimetric system distinguishing cyanide from anions

Hydrazone-based receptors, containing fluorene-skeleton substituents, in a THF solution, in the presence of fluoride or cyanide, do not only form H-bond complexes, but mainly undergo deprotonation of the N–H fragments, an event, which is signaled by the color change, the ability of the deprotonation is associated with the fluorene skeleton. The deprotonation process is also reversible by the addition of metal ions, while cyanide from fluoride could be distinguished by the addition of copper (II).     

Lanthanide Complexes that Respond to Changes in Cyanide Concentration in Water

Cyanide ions are shown to interact with lanthanide complexes of phenacylDO3A derivatives in aqueous solution, giving rise to changes in the luminescence and NMR spectra. These changes are the consequence of cyanohydrin formation, which is favored by the coordination of the phenacyl carbonyl group to the lanthanide center. These complexes display minimal affinity for fluoride and can detect cyanide at concentrations less than 1 μm . By contrast, lanthanide complexes with DOTAM derivatives display no affinity for cyanide in water, but respond to changes in fluoride concentration.     

Colorimetric detection of cyanide with a chromogenic oxazine

[reaction: see text] We have designed a chromogenic oxazine for the colorimetric detection of cyanide. Indeed, the [1,3]oxazine ring of our compound opens to form a 4-nitrophenylazophenolate chromophore in response to cyanide. This quantitative chromogenic transformation permits the detection of micromolar concentrations of cyanide in water. Furthermore, our chromogenic oxazine is insensitive to the presence of large concentrations of fluoride, chloride, bromide, or iodide anions, which are generally the principal interferents in the colorimetric detection of cyanide.     

Catalase biosensor for the determination of hydrogen peroxide,fluoride and cyanide

The enzyme catalase, which catalyses the decomposition of hydrogen peroxide to oxygen and water, was immobilized in a membrane by entrapping it in polyacryl amide and contacted to a Clark-type oxygen electrode. With the resulting catalase biosensor it was possible to detect the substrate hydrogen peroxide and the inhibitors fluoride and cyanide in phosphate buffer.The sensor was integrated into a flow system. In the concentration range from 5–200 mg/l a linear dependence of the peak height on the hydrogen peroxide concentration was obtained. The average decrease in activity during 30 days of storage at 6 °C was 17%. Fluoride and cyanide could be determined by measuring the inhibition of the enzymatic reaction in the same flow system. The analysis was executed in three steps; namely determination of the original activity by pumping substrate solution, inhibition of the enzyme by pumping inhibitor solution, and determination of the activity after the inhibition.The decrease in activity correlated with the inhibitor concentration of the sample, but a linear dependence was not found. The inhibition of fluoride and cyanide was both reversible, the enzyme membrane could be reactivated completely by pumping substrate solution. The detection limit was 1 mg/l for fluoride and 1.5 mg/l for cyanide.     

Use of thenoyltrifluoroacetone for the determination of manganese by activation analysis

A new procedure for the substoichiometric extraction of bivalent manganese by thenoyltrifluoroacetone into ethyl acetate has been developed and used in activation analysis. The value of the extraction constant has been found to be 3.1 x 10(-6); the pH range in which the extraction can be performed is 7.8-9.2. The influence of oxalate, citrate, tartrate, fluoride and cyanide ions has been studied. A selective substoichiometric extraction of manganese in the presence of Zr, Hf, Nb, Th, Fe and Sc is possible at pH 8-8.5, tartrate and fluoride being used as masking agents. Copper and cobalt can be screened by ammonia and cyanide respectively. The method has been used for the determination of manganese in biological materials, potassium fluoride and zirconium.     

Solid-state emissive triarylborane-based BODIPY dyes: photophysical properties and fluorescent sensing for fluoride and cyanide ions

We disclose two novel BODIPY dyes, which contain the bulky substituent, [(4-dimesitylboryl)phenyl]ethynyl at 2- and 2,6-positions. The steric bulkiness of the boryl group is effective to suppress the intermolecular interaction in the solid state and thus these two compounds display intense fluorescence not only in solution but also in the solid state. In addition, the BODIPY dyes display sensitive fluorescence responses to fluoride and cyanide anions through the complexation with the boron center of the boryl group and the subsequent decomposition of the BODIPY core, illustrating their potential uses for the fluorescence sensing of fluoride and cyanide ions.     

A novel glycoconjugated N-acetylamino aldehyde hydrazone azo dye as chromogenic probe for cyanide detection in water

A new selective chemodosimeter probe of cyanide anions in aqueous media was developed by the introduction of a simple glyco-conjugated o-(carboxamido) aldehyde hydrazone into an azo dye as chemodosimeter that recognizes cyanide anions among other competing anions such as acetate, dihydrogen phosphate, fluoride through reversible covalent bonding. The sensing properties of the new materials were investigated in pure water and have demonstrated a very high selectivity toward the cyanide anions. The detection limit of the new chromogenic probe was measured to be 1.29 μM which is much lower than most recently reported chromogenic probes for cyanide determination.     

Triarylboranes with a 2‐Dimesitylboryl‐2’‐(N,N‐dimethylamino)biphenyl Core Unit: Structure–Property Correlations and Sensing Abilities to Discriminate Between F− and CN− Ions

A series of triarylboranes, in which different substituents are introduced at the para position of the dimethylamino group of a 2‐dimesitylboryl‐2’‐(N,N‐dimethylamino)biphenyl core unit, have been comprehensively investigated to explore the effect of structural modification on photophysical properties. The introduction of electron‐accepting substituents would facilitate the HOMO→LUMO charge transfer (CT) transition. In contrast, the intramolecular CT transition is significantly prohibited when electron‐donating substituents are incorporated. Notably, the HOMO→LUMO CT transition mainly consists of the transition from the electron‐donating amino group to an electron acceptor other than boryl when a strong electron acceptor such as the dicyanovinyl group is present. This dicyanovinyl‐substituted compound displays sensing abilities to discriminate fluoride and cyanide ions. In solution in THF, the fluoride ions first bind to the boron center, then attack the α‐carbon atom of the dicyanovinyl group, whereas the cyanide anion acts on the electron‐accepting centers in the reverse sequence. As a result, the absorption and emission change in different manners upon addition of fluoride and cyanide ions.     

Mutual separation of Co(II), Fe(III), Eu(III) and Tb(III) on HTTA-loaded polyurethane foam

The selectivity of the 2-thenoyltrifluoroacetone (HTTA) loaded polyurethane (PUR) foam as adsorbent was studied. The influence of various anions on the adsorption indicated that permanganate, oxalate, EDTA, and citrate formed strong complexes with the metal ions and masked completely, while phosphate, thiosulphate, cyanide, ascorbate, tartrate and fluoride hindered the sorption of Fe(III). The sorption of Co(II) is also prohibited in presence of anions like cyanide, ascorbate and tartrate. The sorption of Eu(III) and Tb(III) is greatly affected in the presence of phosphate and fluoride. A group separation of different metals has been proposed on the basis of selectivity of the foam.     

Luminescence lifetime-based sensor for cyanide and related anions

A new Ru(II) complex is described which serves as a luminescence lifetime-based sensor for fluoride and cyanide anions (KF = 640 000 mol-1, KCN = 430 000 mol-1). This chromophore displays observable changes in its UV-vis and steady-state luminescence spectra upon cyanide binding. Prior to cyanide addition, this complex exhibits a single-exponential lifetime (tau = 377 +/- 20 ns). With increasing cyanide concentrations, the intensity decays are composed of two exponentials: long tau (320-370 ns) and short tau (13-17 ns). The average lifetimes shorten as a function of cyanide concentration since the fractional intensity shifts from an initial dominant long lifetime component to the short lifetime component. This work represents the first example of a direct method for the luminescence lifetime-based sensing of anions.     

Straightforward Synthesis of 1,2‐Dicyanoalkanes from Nitroalkenes and Silyl Cyanide Mediated by Tetrabutylammonium Fluoride

A straightforward synthesis of 1,2‐dicyanoalkanes by reacting nitroalkenes with trimethylsilyl cyanide in the presence of tetrabutylammonium fluoride is described. The reaction proceeds through a tandem double Michael addition under mild conditions. Employing the hypervalent silicate generated from trimethylsilyl cyanide and tetrabutylammonium fluoride is essential for achieving this transformation. Mechanistic studies suggest that a small amount of water included in the reaction media plays a key role. This protocol is applicable to various types of substrates including electron‐rich and electron‐deficient aromatic nitroalkenes, and aliphatic nitroalkenes. Moreover, vinyl sulfones were found to be good alternatives, particularly for electron‐deficient nitroalkenes. The broad substrate scope and functional group tolerance of the reaction makes this approach a practical method for the synthesis of valuable 1,2‐dicyanoalkanes.     

Synthesis of quinolizin-2-one and pyrido[1,2-a]azepin-2-one derivatives from difluoroboron complexes of aroylacetones and O-methyllactims

O-Methyllactims react at the methyl group of difluoroboron complexes of aroylacetones with the formation of condensation products, novel difluoroboron chelates of 1-aryl-4-(piperi-din-2-ylidene)butane-1,3-diones and 1-aryl-4-(azepan-2-ylidene)butane-1,3-diones, which upon the action of concentrated HCl in ethanol are transformed into the corresponding quino-lizin-2-one and pyrido[1,2-a]azepin-2-one derivatives.     

The semi-micro determination of fluorine,chlorine, and nitrogen in organic compounds: The use of cation exchange resins

The organic compounds are fused in a nickel bomb with sodium in the usual way. If no oxygen is present, the nitrogen is determined as cyanide by Deniges' method. After destruction of cyanide with formaldehyde the total chloride and fluoride is determined by passing the solution through a cation exchange column and determining total acidity in the eluate. The chloride in the same or a separate eluate is then determined by treatment with mercuric oxycyanide or by titration with silver nitrate.     

Bifunctional maleimide dyes as selective anion sensors

A class of disubstituted maleimide dyes with two symmetrical NH binding sites was found to exhibit distinct color change and fluorescence quenching effect for fluoride, cyanide, and dihydrogen phosphate anions. The intense red emission displayed apparent solvatochromic shift, indicating a strong charge-transfer character. The interactions between the dyes and anions were variable depending on the amine substituents at C(3,4) of the maleimides. For the dyes with two pyrrolyl receptor sites, the NH protons were deprotonated by more basic anions such as fluoride or cyanide. For those with two indolyl receptor sites, formation of a chelate with H₂PO₄⁻ through hydrogen bonds played a major role.     

Biosourced 3-formyl chromenyl-azo dye as Michael acceptor type of chemodosimeter for cyanide in aqueous environment

A simple water-soluble aldehyde functionalized chromone 5 was utilized as a doubly activated Michael acceptor type of chemodosimeter for cyanide in water. The water solubility of the probe 5 is due to the incorporation of two glycerol units on the starting prepared chemodosimeter. This sensory system is able to selectively distinguish cyanide among fluoride and many other anions at micromolar concentrations and instantly detect cyanide in water at ambient temperatures with a detection limit down to 1.0 mM. Thus, the chemodosimeter 5 was applied to the quantitative determination of cyanide anion in drinking water sample (drinking water from commence).     

Evaluation of experimental conditions on the response of fluoride and cyanide selective electrodes in flow injection potentiometry

Summary The response of fluoride and cyanide selective electrodes has been investigated under steady-state and flow injection measuring conditions. Response time measurements indicate that at lower concentration levels of these ions the surface condition for both sensors is very critical; the choice of flow cell geometry, however, is of minor importance. An acetate buffer without CDTA is proposed for fluoride determinations because of better long term stability of response time of the fluoride ISE. Problems associated with the corrosion of the AgI-membrane when applied in a flow cell with wall-jet configuration are discussed.Dedicated to Prof. Dr. G. Schulze on the occasion of his 60th birthday