The B(C6F5)3·H2O promoted synthesis of fluoroalkylated 3,3',3''-trisindolylmethanes from fluorocarboxylic acids and indoles

Trisindolylmethanes (TIMs) exist in many bioactive natural products and are frequently applied in medicinal chemistry and materials science. Herein, a simple and efficient protocol promoted by B(C₆F₅)₃·H₂O for the synthesis of their fluoroalkylated analogues, fluoroalkylated 3,3',3''-TIMs, is reported for the first time. Easily accessible fluorocarboxylic acids are utilized as the fluoroalkyl sources, exhibiting an obvious fluorine effect. This convenient and green process features mild and metal-free conditions, easy scale-up, and an environmentally friendly byproduct.

Tuning anion binding properties of Bis(indolyl)methane Receptors: Effect of substitutions on optical responses

Chromogenic probes based onoxidizedbis(indolyl)methanes have been synthesized with varying substituents (R = -Me [1], -OMe [2], -OH, [3]) on the central aryl ring. In addition to electronic influence, the involvement of substituents in ion-dipole and charge-assisted hydrogen bonding interactions significantly alters the solvatochromic response and pH-sensitive behavior. In polar aprotic solvents, like CH₃CN, a concentration-dependent stepwise color change was observed with F^- ions. In the case of2, a reversible hydrogen bonding interaction between the deprotonated probe and HF₂^- dimer might be responsible for that, while step-wise deprotonation caused by F^- ions could be the probable reason with3. Since the formation of HF₂^- is energetically unfavorable in a polar protic solvent, the response of 2 with F^- ions appears to be very different in EtOH medium. Interestingly, no such alteration in anion sensing behavior was noticed with3going from an aprotic to a protic solvent.

A new 5-bromoindolehydrazone anchored diiodosalicylaldehyde derivative as efficient fluoro and chromophore for selective and sensitive detection of tryptamine and F- ions: Applications in live cell imaging

A novel indole hydrazone tagged moiety, 2-((5-bromo-1H-indol-2-yl) methylene) hydrazono) methyl)-4, 6-diiodophenol (BHDL) has been developed for the selective and sensitive detection of biogenic tryptamine and F^- ions. The binding dexterity of probe BHDL towards F^-/tryptamine (TryptA) has been investigated by UV-visible/fluorescence spectroscopy. In the presence of TryptA, probe exhibits strong enhancement in the emission band at 433 nm and the band at 555 nm underwent a blue shift accompanied by a decrease in intensity by the inhibition of Excited State Intramolecular Proton Transfer (ESIPT) on BHDL. Excitingly, complexation with F^- ions as well triggers an enhancement in a fluorescence band at 430 nm with the concomitant disappearance of the emission band at 555 nm due to the inhibition of ESIPT and deprotonation process initiated by the hydrogen bonding complex formation. Further, Density Functional Theoretical (DFT) calculations have been performed to support the mechanism functioned on the probe BHDL in the presence of TryptA/F^-.

Carbazole sulfonamide-based macrocyclic receptors capable of selective complexation of fluoride ion

Two carbazole sulfonamide-based macrocycles 1 and 2 were facilely synthesized and carefully evaluated for their anion recognition properties. The obtained results revealed that macrocycle 1 with a 1,3-xylyl linker was able to bind fluoride ion more strongly and selectively in acetonitrile medium than its strong competitors (like acetate and dihydrogen phosphate anions), with a large binding constant (K_a) of 50 878 M⁻¹. More importantly, an exclusive fluoride recognition was achieved for macrocycle 1 in the more polar DMSO-d₆ solution, albeit with a moderate affinity of K_a = 147 M⁻¹. Compared with macrocycle 1, macrocycle 2 bearing a 2,6-lutidinyl linkage exhibited a remarkable change not only in the anion affinity but also in the anion selectivity, although with only a slight difference in their molecular structures.

Two carbazole sulfonamide-based macrocycles 1 and 2 were facilely synthesized and carefully evaluated for their anion recognition properties.

An approach to unsymmetrical 3,3′-diindolylmethanes through Pd-catalyzed cascade Heck cyclization of allenamides and o-ethynylanilines

A highly efficient synthesis of unsymmetrical 3,3′-diindolylmethanes has been developed by palladium-catalyzed cascade Heck/cyclization reaction.

Selective detection of fluoride via amplified donor-acceptor interaction of 6H-indolo[2,3-b]quinoline

In this report, 6H-indolo[2,3-b]quinoline (hereafter 2a) was synthesized and employed as an optical chemosensor for fluoride. The sensitivity of 2a towards fluoride was established from the change in both the absorption and emission signals. The various in-situ¹H NMR, UV-Vis, and density functional studies indicate that the 1:2 binding interaction between 2a and fluoride followed by deprotonation to its corresponding di-anion (2a^2-), which in turn boosted the donor-acceptor interaction between indole and quinoline moiety in 2a^2-via expansion of torsion angle by 10.2° as compared to 2a. Consequently the significant changes in both the absorption and emission signal of 2a allow us to detect and estimate the concentration of fluoride up to 0.2 μM from the mixture of different anions.

Synthesis, recognition and sensing properties of dipyrrolylmethane-based anion receptors

Two tweezer-like anion receptors 2,2'‑bis(2‑cyano‑2‑phenylvinyl)‑5,5'‑dimethyl dipyrromethane (1) and 2,2'‑bis[2‑cyano‑2‑(4‑nitrophenyl)vinyl]‑5,5'‑dimethyl dipyrromethane (2) were synthesized in good yields, via a facile condensation of diformyldipyrromethane and the appropriate phenylacetonitrile. Anion recognition properties of these receptors were studied in detail in DMSO solution, by means of UV-vis and ¹H NMR titration techniques. The obtained results indicated that receptor 2 containing a terminal nitro group exhibited the strong and selective binding to biologically important fluoride and dihydrogenphosphate ions over other anions. In addition, the binding strength of receptor 2 with fluoride was enhanced by a factor of 18, relative to receptor 1 lacking the nitro group. Remarkably, the presence or absence of nitro group within receptor compounds also had a great influence on the anion-binding selectivity. In particular, a distinct color change of DMSO solution of receptor 2 was observed only upon addition of fluoride, showing the potential of 2 acting as an effective colorimetric sensor for the detection of fluoride anion.

Preparation of a graphene oxide/silica composite modified with nitro-substituted tris(indolyl)methane as a solid-phase extraction sorbent for the extraction of organic acids

This paper describes the use of graphene oxide/silica modified with nitro-substituted tris(indolyl)methane as a solid-phase extraction sorbent for the determination of organic acids. The resultant graphene oxide/silica modified with nitro-substituted tris(indolyl)methane was characterized by FTIR spectroscopy and adsorption experiments. Solid-phase extraction parameters such as sorbent type, sample solution pH, sample loading rate, eluent salt concentration, eluent methanol concentration, elution rate, sample loading, and elution volume were optimized. The method showed good precision, accuracy, sensitivity, and linear response for organic acids analysis over a concentration range of 1-100 μg/L for benzoic acid, p-methoxybenzoic acid, and salicylic acid and 5-100 μg/L for the remaining organic acids (cinnamic acid, p-chlorobenzoic acid, and p-bromobenzoic acid) with coefficients of determination (r(2) ) of higher than 0.9957. Limits of detection from 0.50 to 1.0 μg/L for six organic acids were achieved. The developed method was successfully applied to determine organic acids in real samples.

A facile one-pot method to synthesise 2-alkylated indole and 2,2′-bis(indolyl)methane derivatives using ketones as electrophiles and their anion sensing ability

Indole derivatives are of great importance because of their biological activity and application in technology.

Synthesis, characterization and photophysical properties of some 3,3′-bisindolyl(aryl)methanes

A series of 3,3′-bisindolyl(aryl)methanes were synthesized and fully characterized by a combination of¹H and¹³C NMR spectroscopy and in one case using X-ray crystallography.

Colorimetric detection of anions in aqueous media using N-monosubstituted diaminomaleonitrile-based azo-azomethine receptors: real-life applications

New N-monosubstituted diaminomaleonitrile-based azo-azomethine dyes have been synthesized in order to develop colorimetric sensors for detection of biologically important anions in aqueous media. Importantly, the reported sensor decorated with strong electron-withdrawing group can detect inorganic fluoride in water even at 0.037 ppm level, which is lower than WHO permissible level (below 1 ppm). Successfully, the prepared dyes were used for qualitative and quantitative detection of inorganic fluoride in toothpaste and mouthwash. The anion recognition mechanism was also investigated by detailed UV-Vis and (1)H NMR experiments. The detailed (1)H NMR experiments corroborated that anion recognition is based on the deprotonation phenomenon.

An efficient solvent-free synthesis of bis(indolyl)methane-based naked eye chemosensor for Cu2+ion from β-chloro-α,β-unsaturated aldehydes using PMA-Cellulose as a solid phase reusable catalyst

A green one pot synthesis of novel bis(indolyl)methanes as naked eye chemosensors towards Cu²⁺ion has been developed from β-chloro-α,β-unsaturated aldehydes using new reusable solid acid support/catalyst PMA-Cellulose.

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 μM via ratiometric responses.

Two and three input molecular logic operations mediated by a novel azo-azomethine based chromogenic probe through intramolecular charge transfer processes

A novel azo-azomethine based chromogenic receptor has been successfully designed and synthesized for the construction of multifunctional molecular logic circuits.

Naked-eye detection of biologically important anions by a new chromogenic azo-azomethine sensor

A new chromogenic azo-azomethine sensor, containing active phenolic sites, has been designed and synthesized via condensation reaction of N,N,N',N'-tetrakis(2-aminoethyl)-2,2-dimethyl propane-1,3-diamine with 1-(3-formyl-4-hydroxyphenylazo)-4-nitrobenzene. The anion recognition ability of the synthesized receptor was evaluated using UV-Vis spectroscopy and (1)H NMR technique. The anion recognition studies exhibited that the receptor acts as a sensor for biologically important anions such as F(-), AcO(-) and H2PO4(-) over other anions. The binding stoichiometry between sensor and anions was found to be 1:2. (1)H NMR experiment revealed that sensor recognizes anions via H-bonds and subsequent deprotonation to elicit a vivid color change. Interestingly, the sensory system not only let for the naked eye detection without any spectroscopic instrumentation but also helped to discriminate between anions.

Differentiation of Functional Groups and Biologically Relevant Anions Using AT-PAMAM Dendrimers

Biological anions have often proven to be difficult analytes to differentiate in solution. Many of the anions bear similar structural characteristics and similar charge states. Using a commercially available indicator and AT-PAMAM dendrimers, a sensing ensemble for a number of biological anions was constructed. The system was able to identify each of the different analytes as well as the regioisomers of three different tricarboxylates. The system shows responsiveness to not only functional group identity but also the charge state and identity of the anionic species.

Chromogenic and fluorogenic chemosensors and reagents for anions. A comprehensive review of the years 2010-2011

This review focuses on examples reported in the years 2010-2011 dealing with the design of chromogenic and fluorogenic chemosensors or reagents for anions.