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A dimethylaniline (donor)‐indanedione (acceptor) conjugate (sensor 1) with a very low molecular weight of 277 g mol−1 and intramolecular charge transfer (ICT) characteristics was synthesized. Sensor 1 shows weak ICT fluorescence in solution, but strong emission (Φ=16%) in the solid state owing to intramolecular and intermolecular C−H⋅⋅⋅O hydrogen bonds that inhibit the free rotation of the exocyclic C−C single bond. Compared to yellow emitter 1Y, which has a similar donor‐acceptor structure, sensor 1 shows red fluorescence in the solid state owing to J‐aggregate formation. The colorimetric and fluorometric responses of sensor 1 to cyanide in both solution and solid state are due to the nucleophilic addition of cyanide to the β‐conjugated carbon of the indanedione group, which prohibits ICT. Additionally, inexpensive portable paper‐based test kits based on sensor 1 were easily prepared and could be used for fast and quantitative naked‐eye cyanide detection in real time. [ABSTRACT FROM AUTHOR]

The article "Pyrene-Phosphonate Conjugate: Aggregation-Induced Enhanced Emission, and Selective Fe3+ Ions Sensing Properties" published in Molecules in 2017 has been retracted due to concerns raised by the Royal Melbourne Institute of Technology (RMIT) regarding an image and the validity of the findings. An investigation conducted by the Editorial Board and Editorial Office, including input from RMIT, found overlapping elements in Figure 1 and a lack of raw material to verify the presented findings. As a result, the article was retracted in accordance with MDPI's retraction policy and the Committee on Publication Ethics guidelines. The authors agreed to the retraction, while others did not provide a comment on the decision. [Extracted from the article]

An indole‐indanedione‐based small molecule, compound 1Me, comprising an intramolecular C−H⋅⋅⋅O hydrogen‐bond (H‐bond) and with an intramolecular charge transfer (ICT) characteristic was prepared for the colorimetric and fluorometric detection of CN−. Compound 1Me is virtually nonfluorescent in solution but emits a strong yellow fluorescence in the solid state because of the intramolecular C−H⋅⋅⋅O H‐bond, which inhibits the free rotation of the exocyclic C−C single bond of 1Me. The nucleophilic addition of CN− to the β‐conjugated carbon of the indanedione group of 1Me, which breaks the intramolecular C−H⋅⋅⋅O H‐bond and blocks ICT, causes the colorimetric and fluorometric responses of 1Me to CN−. Furthermore, inexpensive and portable paper‐based test kits containing 1Me could be used to rapidly and conveniently sense CN− using the naked eye in real time. The results provide a new strategy for designing colorimetric and fluorometric cyanide‐selective sensors based on an intramolecular C−H⋅⋅⋅O hydrogen bonded solid emitter. [ABSTRACT FROM AUTHOR]

A pyrene-based probe bearing benzothiazole ionophore (Py-BTZ) was synthesised as a “turn-on” fluorescent chemosensor for the detection of Fe3+ and Fe2+ ions in CH3CN : H2O (1 : 1, v/v) solvent mixes. The chemosensor showed optical as well as colorimetric changes towards Fe3+ and Fe2+ ions along with a remarkable enhancement in fluorescence emission. The detection limit of Py-BTZ towards Fe3+ and Fe2+ ions was found to be 2.61 μM and 2.06 μM, respectively. The binding of Py-BTZ with Fe3+ and Fe2+ was determined by using FT-IR experiments. Interestingly, Py-BTZ shows aggregation induced emission enhancement (AIEE) properties in polar solvent mixes such as CH3CN : H2O (1 : 1, v/v). [ABSTRACT FROM AUTHOR]

A new pyrene-phosphonate colorimetric receptor 1 has been designed and synthesized in a one-step process via amide bond formation between pyrene butyric acid chloride and phosphonate-appended aniline. The pyrene-phosphonate receptor 1 showed aggregation-induced enhanced emission (AIEE) properties in water/acetonitrile (ACN) solutions. Dynamic light scattering (DLS) characterization revealed that the aggregates of receptor 1 at 80% water fraction have an average size of ≈142 nm. Field emission scanning electron microscopy (FE-SEM) analysis confirmed the formation of spherical aggregates upon solvent evaporation. The sensing properties of receptor 1 were investigated by UV-vis, fluorescence emission spectroscopy, and other optical methods. Among the tested metal ions, receptor 1 is capable of recognizing the Fe3+ ion selectively. The changes in spectral measurements were explained on the basis of complex formation. The composition of receptor 1 and Fe3+ ions was determined by using Job's plot and found to be 1:1. The receptor 1--Fe3+ complex showed a reversible UV-vis response in the presence of EDTA. [ABSTRACT FROM AUTHOR]

A new selective and sensitive HSO4-ion receptor based on fused pyridopyrimidine was developed. The detection of HSO4-over other anions such as Cl-, F-, Br-, I-, ClO4-, H2PO4-, NO3-, and AcO- was confirmed by fluorescent color changes, UV-vis and fluorescence spectroscopy. The HSO4- ion binding with the receptor was also investigated with a binding constant 1.09387 x 105 M-1, which revealed that the receptor showed a remarkable binding ability towards the HSO4- ion. The limit of detection was calculated to be 6.0378 x 10-5 M in ACN:H2O (1:3, v:v) solvent mixture. [ABSTRACT FROM AUTHOR]

Quinoxaline-based novel acid-responsive probe Q1 was designed on the basis of a conjugated donor-acceptor (D-A) subunit. Q1 shows colorimetric and fluorometric changes through protonation and deprotonation in dichloromethane. With the addition of the trifluoroacetic acid (TFA), UV-vis absorption spectral changes in peak intensity of Q1 was observed. Moreover, the appearance of a new peaks at 284 nm 434 nm in absorption spectra with the addition of TFA indicating protonation of quinoxaline nitrogen and form Q1.H+ and Q1.2H+. The emission spectra display appearance of new emission peak at 515 nm. The optical property variations were supported by time resolved fluorescence studies. The energy band gap was calculated by employing cyclic voltammetry and density functional calculations. Upon addition of triethylamine (TEA) the fluorescence emission spectral changes of Q1 are found to be reversible. Q1 shows color changes from blue to green in basic and acidic medium, respectively. The paper strip test was developed for making Q1 a colorimetric and fluorometric indicator. [ABSTRACT FROM AUTHOR]

A new pyrene-phosphonate colorimetric receptor 1 has been designed and synthesized in a one-step process via amide bond formation between pyrene butyric acid chloride and phosphonate-appended aniline. The pyrene-phosphonate receptor 1 showed aggregation-induced enhanced emission (AIEE) properties in water/acetonitrile (ACN) solutions. Dynamic light scattering (DLS) characterization revealed that the aggregates of receptor 1 at 80% water fraction have an average size of ≈142 nm. Field emission scanning electron microscopy (FE-SEM) analysis confirmed the formation of spherical aggregates upon solvent evaporation. The sensing properties of receptor 1 were investigated by UV-vis, fluorescence emission spectroscopy, and other optical methods. Among the tested metal ions, receptor 1 is capable of recognizing the Fe 3+ ion selectively. The changes in spectral measurements were explained on the basis of complex formation. The composition of receptor 1 and Fe 3+ ions was determined by using Job's plot and found to be 1:1. The receptor 1 -Fe 3 + complex showed a reversible UV-vis response in the presence of EDTA., Competing Interests: The authors declare no conflict of interest.