Anthraquinone Based Sensors for the Selective Detection of Cyanide Ion with Turn on Fluorescence with Logic Gate & Real Sample Applications

In recent years, there is an increasing interest in finding better and more efficient ways to detect CN- ions. Most of the anthraquinone-based probes show less fluorescence This paper presents the design and synthesis of a new anthraquinone based imine probe with good colorimetric sensing property and fluorescent turn on behavior toward CN- ion. Herein, we report a receptor with both colorimetric and fluorescent enhancement of cyanide ion in DMSO medium is synthesized. The synthesized receptor shows an immediate color change from orange to pink when cyanide is added; and it can be readily observed visually due to the presence of diverse p-conjugated systems in the receptor. These studies were confirmed by UV-Visible, PL studies, DFT, HRMS and 1H NMR titration. Moreover, this receptor shows 1:1 stoichiometry and micromolar detection limit. Further the receptor was applied to a real sample in finger millet (Eleusine Coracana) to detect the presence of cyanide ion. Moreover, the receptor is applicable toward INHIBITION, IMPLICATION logic gates with two input systems.

Exploring the Mechanism of Anionic Chemosensing by Imidazoles: A Review

Chemosensing of ions has gained considerable attention by chemists. Insight into the mechanism involved between sensors and ions always fascinates researchers to develop economical, sensitive, selective, and robust sensors. This review comprehensively explores the mechanism of interaction between Imidazole sensors and anions. With most of the research concentrating only on fluoride and cyanide, this review has highlighted a large gap in various anions detection including SCN^-, Cr₂O₇^2-, CrO₄^2-, H₂PO₄^-, NO₂^-, and HSO₄^-.This study also includes a critical analysis of different mechanisms and their respective limits of detection, with a discussion of the reported results.

Light and Cation-Driven Optical Switch based on a Stilbene-Appended Terpyridine System for the Design of Molecular-Scale Logic Devices

A molecular system comprising a terpyridine moiety capable of coordinating with different cations and a photoswitchable stilbene unit has been utilized here for the fabrication of multiply configurable logic systems. Incorporation of a substituted stilbene unit into the terpyridine motif generates an intraligand charge-transfer-sensitive module whose absorption and emission spectral properties are highly sensitive to light as well as cations. On the basis of the optical response profile of the receptor in the presence of selected cations as well as light of a specific wavelength, we are able to demonstrate multiple Boolean logic functions such as INHIBIT, IMPLICATION, OR, NOR, and NAND, as well as various combinations of them. Of particular interest, we utilized the present system for the construction of security keypad locks and memory devices by maintaining a proper sequence of the stimuli and monitoring either absorption or emission spectral response at a specific wavelength as the output signal. In addition to various Boolean logic functions, the present system has also the ability to mimic fuzzy logic operations for generating an infinite-valued logic scheme depending on its emission spectral responses upon varying the concentration of cationic (Fe²⁺ and/or Zn²⁺) and anionic (CN^-) inputs.

Comparative study of the photophysical and crystallographic properties of 4-(9H-pyreno[4,5-d]imidazol-10-yl)phenol and its alkylated derivatives

The photophysical and crystallographic properties of a para-hydroxphenyl-substituted pyrenoimidazole and its decylated analogues were investigated. The fluorescence of these compounds is sensitive to environmental acidity and basicity.

Fluorescence Sensors for Bismuth (III) Ion from Pyreno[4,5-d]imidazole Derivatives

Three pyreno[4,5-d]imidazole derivatives are synthesized and evaluated as fluorescent sensors for bismuth (III) ion. The target compounds are prepared in 55-86% yields from a condensation reaction between pyrene-4,5-dione and aromatic aldehydes. The compound bearing a phenolic group can selectively detect bismuth (III) ion via fluorescence enhancement with a detection limit of 1.20 μm in CH₃ CN-DMSO mixture and 3.40 μm in 10% pH5 aqueous in CH₃ CN-DMSO mixture. The sensing mechanism involving a formation of coordination complex is investigated by UV-VIS and fluorescence titrations, ¹ H-NMR and the decomplexation of the bismuth complex by sulfide ion. The application of this sensor for quantitative analysis of spiked bismuth (III) ion in real water samples from two different sources is demonstrated.

Rationally designed imidazole derivative as colorimetric and fluorometric sensor for selective, qualitative and quantitative cyanide ion detection in real time samples

A new imidazole derivative of 1,2-diaminoanthraquinone and fluorene-2-carboxaldehyde was designed as a sensor B2 to selectively detect the cyanide (CN^-) ion through colorimetric and/or fluorometric methods. The photochemical characterizations of sensor B2 were tested using absorption and emission spectral studies in CH₃CN-H₂O (8:2) semi-aqueous medium. An excited state proton transfer process (ESIPT) was proved by theoretical and spectral studies. The colorimetric and fluorescence detection limit of CN^- ion was found to be 5.3 × 10^-6 M and 4.11 × 10^-8 M, respectively. ¹H NMR titration, electrochemical and DFT studies were supported the removal of -NH proton from B2. In order to utilize this sensor in real-time applications, we developed a test cassette which is coated with sensor B2 detected the presence of CN^- ion in the food sample with endogenous cyanide ion.

Tandem Detection of Sub-Nano Molar Level CN- and Hg2+ in Aqueous Medium by a Suitable Molecular Sensor: A Viable Solution for Detection of CN- and Development of the RGB-Based Sensory Device

An inimitable urea-based multichannel chemosensor, DTPH [1,5-bis-(2,6-dichloro-4-(trifluoromethyl)phenyl)carbonohydrazide], was examined to be highly proficient to recognize CN- based on the H-bonding interaction between sensor -NH moiety and CN- in aqueous medium with explicit selectivity. In the absorption spectral titration of DTPH, a new peak at higher wavelength was emerged in titrimetric analytical studies of CN- with the zero-order reaction kinetics affirming the substantial sensor-analyte interaction. The isothermal titration calorimetry (ITC) experiment further affirmed that the sensing process was highly spontaneous with the Gibbs free energy of -26 × 104 cal/mol. The binding approach between DTPH and CN- was also validated by more than a few experimental studies by means of several spectroscopic tools along with the theoretical calculations. A very low detection limit of the chemosensor toward CN- (0.15 ppm) further instigated to design an RGB-based sensory device based on the colorimetric upshots of the chemosensor in order to develop a distinct perception regarding the presence of innocuous or precarious level of the CN- in a contaminated solution. Moreover, the reversibility of the sensor in the presence of CN- and Hg2+ originated a logic gate mimic ensemble. Additionally, the real-field along with the in vitro CN- detection efficiency of the photostable DTPH was also accomplished by using various biological specimens.

Dual mode detection of CN- & Cu2+ using fluorene moiety with logic gate, DFT studies and real sample analysis applications

A simple colorimetric receptor was synthesized by the condensation of 2-amino fluorene with 2-hydroxy-5-nitrobenzaldehyde and its properties were investigated using colorimetric, fluorescence and DFT studies. The sensing mechanism was ascertained by ¹H NMR titration studies. The synthesized receptor showed two-pronged chemosensing properties and exhibited remarkable colorimetric transitions from colorless to yellow in the presence of CN^- and colorless to green in the presence of Cu²⁺ in 80:20 acetonitrile/water medium, which could be determined by naked eye observations. The detection limit of receptor to CN^- and Cu²⁺ ion was found to be 7.9 × 10^-7 M and 4.5 × 10^-8 M respectively. Receptor was also successfully employed in the construction of molecular INHIBIT and YES logic gates. The synthesized receptor was also efficiently used for real-sample analysis in Finger Millet, also known as Ragi in Tamil. Its scientific name is Eleusine coracana.

Excitation wavelength as logic operator

Multiple molecular logic gates were harvested on a single synthesized material, (E)-2-(2-hydroxy-3-methoxybenzylideneamino)phenol (MBAP), by combining excitation wavelength dependent multi-channel fluorescence outputs and the same chemical inputs. Interestingly, the effortless switching of logic behavior was achieved by simply tweaking the excitation wavelength and sometimes the emission wavelengths with no alteration of chemical inputs and the main device molecule, MBAP. Additionally, new generation purely optically driven memory units were designed on the same system supporting an almost infinite number of write-erase cycles since inter-conversion of memory states was completely free from chemical interferences and impurity issues. Two-way memory functions ("erase-read-write-read" and "write-read-erase-read") worked simultaneously on the same system and could be accessed by simple optical switching between two excitation and emission wavelengths. Our optically switchable device might outperform traditional multifunctional logic gates and memory devices that generally employ chemical triggers to switch functionality and memory states. These optically switchable multifunctional molecular logic gates and memory systems might drive smart devices in the near future with high energy efficiency, extended life span, structural and functional simplicity, exclusive reversibility and enhanced data storage density.

Naphthalimide based smart sensor for CN−/Fe3+ and H2S. Synthesis and application in RAW264.7 cells and zebrafish imaging

Probe R designed as tailor-fit triple action smart chemosensor for the sequential detection of CN⁻ and Fe³⁺via colorimetric and fluorometric ‘on–off’ method and H₂S through colorimetric method in semi-aqueous conditions.

Design and synthesis of new functionalized 8-(thiophen-2-yl)-1,2,3,4-tetrahydroquinolines as turn-off chemosensors for selective recognition of Pd2+ ions

Functionalized 8-thienyl-1,2,3,4-tetrahydroquinoline was synthesized as a fluorescent turn-off chemosensor for selective recognition of Pd²⁺ ions with a low detection limit.

Self-Condensation of Pyrene-4,5-dione: An Approach To Generate Functional Organic Fluorophores

A new class of π-conjugated organic fluorophores containing a 6H-phenanthro[4,5-cde]pyreno[4',5':4,5]imidazo[1,2-a]azepin-6-one core was synthesized by a facile one-pot condensation method. The molecular structures and solid-state packing properties of these compounds were investigated by X-ray single crystallographic analysis. UV-vis absorption and fluorescence spectroscopic studies disclosed interesting mechanofluorochromic properties in the solid state and highly sensitive acidochromic behavior in the solution phase.

Selective chromogenic detection of cyanide in aqueous solution - Spectral, electrochemical and theoretical studies

A bisimidazole ensemble (R) possessing naphthoquinone as signaling unit is synthesized and characterized using ¹H and ¹³C NMR and LC-MS spectral techniques. Anion sensing behaviour of the receptor has been investigated using electronic and fluorescence spectral techniques. The receptor exhibits a striking colour change from yellow to brown selectively with cyanide in aqueous HEPES buffer-DMSO (1:1 v/v) medium with a detection limit of 1 μM. Job's continuous variation method suggests that the stoichiometry of the interaction is 1:2 (R:CN^-). The binding constant for receptor-cyanide complex was found to be 8.7 × 10² M^-1. The mechanism of detection of cyanide occurs via deprotonation of imidazole N-H protons, which is well supported by electrochemical study. DFT based theoretical calculations shows that the energy gap between HOMO and LUMO decreases from 3.3086 (in R) to 1.7799 eV (in R + CN^-), which is responsible for the red-shift observed in the UV-Vis spectrum of R upon addition of cyanide ions. The present quinone-bisimidazole based receptor shows few advantages over similar bisimidazoles reported elsewhere.

Pyrenoimidazolyl-Benzaldehyde Fluorophores: Synthesis, Properties, and Sensing Function for Fluoride Anions

Two structural isomers of (9H-pyreno[4,5-d]imidazol-10-yl)-benzaldehyde, with para and meta substitution patterns, were synthesized by condensation of 4,5-pyrenedione with terephthalaldehyde and isophthalaldehyde, respectively. These new pyrenoimidazole derivatives were characterized by single-crystal X-ray crystallography, UV-vis absorption spectroscopy, fluorescence spectroscopy, and cyclic voltammetry to elucidate their structural, solid-state packing, and electronic properties. Interactions of these compounds with fluoride anions in polar organic solvents (acetone and dimethyl sulfoxide) were investigated by NMR, UV-vis, and fluorescence techniques in conjunction with density functional theory calculations. UV-vis analysis showed that the binding of the two pyrenoimidazolyl benzaldehydes with fluoride anions resulted in significant colorimetric responses, while fluorescence studies showed that the para-pyrenoimidazolyl benzaldehyde behaved as an intramolecular charge transfer fluorescent probe, exhibiting ratiometric sensing performance to efficiently detect and quantify fluoride anions at the sub-millimolar level.

A fluorescent turn-on probe for cyanide anion detection based on an AIE active cobalt(ii) complex

A Co(ii) complex based on an AIE-active tetraarylethylene ligand displays selective fluorescence enhancement in the presence of cyanide anion in aqueous solution.

A novel indolium salt as a highly sensitive and selective fluorescent sensor for cyanide detection in water

A highly sensitive fluorescent turn-on cyanide probe is developed based on benzylidenes containing methylindolium group. Three benzylidene derivatives were synthesized from the condensations of three benzaldehyde derivatives and methyleneindoline. Only one of these three derivatives shows strong blue fluorescent response selectively to CN^- which can be clearly observed in submicromolar range as the result of the cyanide addition to the indolium group. The detection of cyanide with this compound is optimized in aqueous media using non-ionic surfactant and sonication method to give very low limit of detection in subnanomolar range. The probe is also developed into a paper-based and gel-based sensing kits that can readily detect cyanide ion in micromolar range by naked eye under a common black light (360nm) illumination.

Homo- and Heterobimetallic Ruthenium(II) and Osmium(II) Complexes Based on a Pyrene-Biimidazolate Spacer as Efficient DNA-Binding Probes in the Near-Infrared Domain

We report in this work a new family of homo- and heterobimetallic complexes of the type [(bpy)2M(Py-Biimz)M'(II)(bpy)2](2+) (M = M' = Ru(II) or Os(II); M = Ru(II) and M' = Os(II)) derived from a pyrenyl-biimidazole-based bridge, 2-imidazolylpyreno[4,5-d]imidazole (Py-BiimzH2). The homobimetallic Ru(II) and Os(II) complexes were found to crystallize in monoclinic form with space group P21/n. All the complexes exhibit strong absorptions throughout the entire UV-vis region and also exhibit luminescence at room temperature. For osmium-containing complexes (2 and 3) both the absorption and emission band stretched up to the NIR region and thus afford more biofriendly conditions for probable applications in infrared imaging and phototherapeutic studies. Detailed luminescence studies indicate that the emission originates from the respective (3)MLCT excited state mainly centered in the [M(bpy)2](2+) moiety of the complexes and is only slightly affected by the pyrene moiety. The bimetallic complexes show two successive one-electron reversible metal-centered oxidations in the positive potential window and several reduction processes in the negative potential window. An efficient intramolecular electronic energy transfer is found to occur from the Ru center to the Os-based component in the heterometallic dyad. The binding studies of the complexes with DNA were thoroughly studied through different spectroscopic techniques such as UV-vis absorption, steady-state and time-resolved emission, circular dichroism, and relative DNA binding study using ethidium bromide. The intercalative mode of binding was suggested to be operative in all cases. Finally, computational studies employing DFT and TD-DFT were also carried out to interpret the experimentally observed absorption and emission bands of the complexes.

A smart switchable module for the detection of multiple ions via turn-on dual-optical readout and their cell imaging studies

A rhodamine based switchable module, RHTH, displays multi-stimuli responses and logic gate based detection of Fe³⁺, Hg²⁺, CN⁻ and S²⁻ ions at ppm levels together with the imaging of these cations in HeLa cell lines.

Selective and sensitive colorimetric sensor for CN− in the absence and presence of metal ions (Cu2+/Ni2+): mimicking logic gate behaviour

Enone based anion sensors have significance due to their colorimetric reaction upon deprotonation and variable occurrence in the conjugated moiety.

Dual anion colorimetric and fluorometric sensing of arsenite and cyanide ions

A naphthalene appended probe, 2-((2-hydroxynaphthalen-1-yl)methylene)hydrazine carbothioamide, was synthesized and found to recognize AsO₂⁻ and CN⁻ ions with turn-on emission fluorescence over different anions in DMF–H₂O (HEPES buffer, 7.2 pH) (9 : 1, v/v solution) medium.

Pyrene-biimidazole based Ru(ii) and Os(ii) complexes as highly efficient probes for the visible and near-infrared detection of cyanide in aqueous media

Pyrenyl-biimidazole based Ru(ii) and Os(ii) complexes are used as highly efficient cyanide sensors in aqueous media.