Vis Titration Research Articles

Heterocyclic-based optical responsive chemosensors for the detection of arsenite and phosphate in semi-aqueous medium: Application in logic gate operations, RGB tool, and DFT studies

Highly selective and sensitive organic chemosensors S2R1-S2R3 were synthesized using thienyl-substituted pyridine derivative and characterized by various spectroscopic techniques. The effect of substituents on selectivity is observed in the chemosensors S2R1 through S2R3, with the rate of reactivity toward ions following the trend as -NO2 > -CN > –OCH3 group. The chemosensor S2R1 exhibited selectivity towards arsenite and phosphate, achieving a Limit of Detection (LOD) of 0.2672 ppm and 0.5042 ppm, respectively, in 30% aq. (CH3)2SO solution. It was also observed that S2R2 was selective for PO43− ions in 100% (CH3)2SO solution with an LOD of 0.521 ppm. The spectral redshifts observed in the organo-aqueous media potentializes the sensor to be colorimetrically active. The probe S2R1 showed the lowest LOD and high binding constant with AsO2− and PO43− ions. Other characterization techniques, such as electrochemical studies, 1H NMR titration, UV–visible titration, and DFT experiments, demonstrated the sensing mechanism of arsenite and phosphate ions with the chemosensors through an intermolecular hydrogen bonding and intermolecular charge transfer (ICT) process followed by its practical applicability for real world-sensing.

Rhodamine 6G derivative for the selective copper detection and remediation using nanoporous diatomaceous earth-engineered functional receptor

A rhodamine-derived receptor was synthesized and comprehensively characterized for structural confirmation. The receptor was able to distinguish the copper ions (Cu2+) from other competing cations. The yellow color of the receptor changed to pink upon adding Cu2+ ions, however, other competing cations ions were impotent towards any color variation. The UV–visible titration studies revealed the binding stoichiometry of a 1:1 ratio with a detection limit of 9.663 × 10−8 M. Additionally, a novel idea of the work resides in the use of diatom for the practical application, where the receptor has been tethered on nanoporous diatomaceous earth microparticles (P2D) to remove Cu2+ ions. The results confirmed that 50 mg receptor functionalized DE could adsorb 10 mL of 1 ppm Cu2+ ions from water. Furthermore, a proof-of-concept device that is inexpensive, simple to operate, and continuously removes Cu2+ ions from water has been developed. The efficiency of the device in Cu2+ ion removal could be realized through the naked eye by observing the color change of P2D particles, which has excellent potential for application in remote locations where water contamination is a significant issue.

1-Naphtholphthalein appended 1,2,3-triazole via CuAAC: A molecular assembly for selective Co(II) ion recognition

Current research work reports the ‘Click’ generation of a ligand, 1- naphtholphthalein linked 1,2,3-triazole (1-NPT) and its “turn-off” absorbance response on binding with Co(II) ions. Copper(I) catalyzed alkyne-azide cycloaddition reaction (CuAAC), a highly stereoselective reaction of ‘Click Chemistry’ is employed to synthesize the five membered heterocyclic ring based probe 1-NPT, that has been successfully characterized by spectroscopic techniques like IR, NMR (1H, 13C) and Mass spectroscopy. The chemosensing behavior of 1-NPT was analyzed by performing UV–Visible titrations with different metal ions like Mn(II), Hg(II), Cd(II), Pb(II), Cu(II), Fe(II), Zn(II), Ba(II), Cr(III), Co(II), K(I) and Na(I) in CH3CN:H2O (4:1, v/v) solution and the results obtained signify the selectivity of synthesized receptor towards Co(II) ions with minimum detection limit of 1.87 µM and 1:1 stoichiometry of 1-NPT:Co(II) complex with no interference of other metal ions.

Blue light emitting fluorophore for the effective detection of cyanide ion and electronic test kit development for real time measurement

This work deals with the blue light emitting fluorophore containing indolium/coumarin fused conjugated system probe JE5, for the effective detection of cyanide ion. The probe holding diethylamino coumarin unit as a donor unit and indolium as an acceptor unit that is connected by a π-conjugation. The cyanide ion sensing ability of the probe has been monitored by UV–visible and fluorescence measurement. The probe exhibits a vivid color change from deep blue to pale yellow before and after sensing cyanide ion. The color change confirmed by visual and UV–visible titration studies. Fluorescence enhancement was observed for the probe after cyanide addition. The obtained color change was due to the disconnection of ICT between the donor and acceptor unit resulting in color change with the added cyanide ion. The limit of detection of the probe JE5 found to be 1.99 μM and 0.97 nM by UV–Visible and fluorescence methods. Electronic device with proper coding data developed for the effective detection of cyanide ion. The stoichiometry of 1:1 binding between JE5 and cyanide ion was obtained.

Ruthenium(II) polypyridyl complexes with benzothiophene and benzimidazole derivatives: Synthesis, antitumor activity, solution studies and biospeciation

With the aim to incorporate pharmacophore motifs into the Ru(II)-polypyridyl framework, compounds [Ru(II)(1,10-phenantroline)2(2-(2-pyridyl)benzo[b]thiophene)](CF3SO3)2 (1) and [Ru(II)(1,10-phenantroline)2(2-(2-pyridyl)benzimidazole)](CF3SO3)2 (2) were prepared, characterized and tested for their antitumor potential. The solid-state structure of the compounds was confirmed by single-crystal X-ray diffraction analysis. The solution behavior of both complexes was investigated, namely their solubility, stability, and lipophilicity in physiological mimetic conditions, as well as an eventual uptake by passive diffusion. In vitro anticancer activity of the complexes on ovarian and different colon cancer cells and apoptosis induction by the complexes were studied. A slow transformation process was observed for complex 1 in aqueous solution when exposed to sunlight, while complex 2 undergoes deprotonation (pKa = 7.59). The lipophilicity of this latter complex depends strongly on the pH and ionic strength. In contrast, 1 is rather hydrophilic under various conditions. Complex 1 was highly cytotoxic on Colo-205 human colon (IC50 = 7.87 μM) and A2780 ovarian (IC50 = 2.2 μM) adenocarcinoma cell lines, while 2 displayed moderate anticancer activity (30.9 μM and 18.0 μM, respectively). The complexes induced late apoptosis and necrosis. Only a weak binding of the complexes to human serum albumin, the main transport protein in blood serum, was found. However, a more significant binding to calf thymus DNA was observed in UV–visible titrations and fluorometric dye displacement studies. Detailed analysis of fluorescence lifetime data collected for the latter systems reveals not only the partial intercalation of the complexes, but goes beyond the usual simplified interpretations.

Design, synthesis, molecular modeling and DNA-binding studies of new barbituric acid derivatives

Cancer disease is developing all over the world mainly in developing countries. We should learn more about DNA–ligand interactions to design new drugs that target biological activities like transcription, replication and translation of particular genes. To understand the mechanism of action and design-specific DNA binders, the evaluation of DNA–ligand interactions is critical. Novel barbituric acid derivatives based on (benzyloxy)benzaldehydes were synthesized and evaluated as DNA-binding agents. Among products, molecular docking studies revealed that 4j and 4m have the best interactions with the ctDNA via the minor groove binding. These results were approved by the quantum mechanics calculations. The interaction profiles of the selected compound (4j and 4m) with DNA were evaluated by UV–Visible titration. UV–Visible titration data confirm this interaction. According to the molecular modeling results, the Structure–Activity relationships for all synthesized barbituric acid derivatives were proposed. It was observed that N,N-dimethyl barbituric acid/4-hydroxybenzaldehyde derivatives have better DNA interactions than barbituric acid/vanillin and barbituric acid/3-hydroxybenzaldehyde derivatives.Supplementary InformationThe online version contains supplementary material available at 10.1007/s13738-022-02576-x.

Investigation on DNA/Protein interaction of thiosemicarbazone based octahedral nickel(II) and iron(III) complexes

2-acetylpyrzine N-(4)-cyclohexylthiosemicarbazide (H2L) and its metal complexes of Ni(II) and Fe(III) have been synthesized. The structure of H2L and corresponding metal complexes are proposed based on the elemental analysis, UV-Visible, FT-IR spectroscopy, and Far IR. It is evident by means of single diffraction X-ray crystallography that there is a distortion in the octahedral geometry owing to the two units of ligands surrounding the metal ion. To exploit the medicinal potential of the complex thus synthesized, their chemical interactions with Bovine Serum Albumin and CT-DNA were studied at normal physiological conditions using UV–Visible, fluorescence spectral, and viscosity measurement techniques. The results obtained from these studies revealed that the complexes exhibit high affinity for DNA with an affinity constant of 106 M−1 and show non-covalent intercalation. The binding constant (Ka) was calculated by using UV–Visible titration from which it is inferred that Ni(II) has more affinity toward CT-DNA compared to Fe(III) complex. Also, it is established by that there were no extrinsic agents responsible for the DNA cleavage by the complexes. Also, absorption and fluorescent techniques were incorporated to study the interactivity of NiL2 and FeL2 with bovine serum albumin (BSA). In-silico methods were adapted to evaluate the DNA-complex interactions. The outcome of experimental as well as in-silico studies suggests that the metal complexes intercalate with the CT-DNA molecules.

Chromone derived effective probe for the detection of metal ion (Cu2+) and chemical explosive (p-nitrotoluene)

A new chromone based Schiff base probe 1,3-bis({[(4-oxo-4H-chromen-3-yl)methylidene]amino})urea (CCH) has been synthesized in one step by the condensation reaction between 3-formylchromone and carbohydrazide in a 2:1 M ratio. The characterization of CCH was done by employing various analytical techniques; FTIR, 1H NMR, 13C NMR, HRMS and FESEM. The probe CCH showed a naked eye colorimetric response from colourless to yellow for the Cu2+ ions with greater selectivity over other metal ions taken for analysis. The binding constant and limit of detection of CCH for Cu2+ ions were calculated to be 4.5 × 105M−1 and 11.4 × 10−7M, respectively, using UV–Visible titrations. The DFT (Density functional theory) results also confirmed the experimental studies. In addition, CCH has shown its applicability for the detection of nitroaromatic compound i.e., p-nitrotoluene (pNT). The sensing mechanism of pNT was studied by UV–Visible and fluorescence studies. A significant quenching of the emission intensity of CCH at 402 nm in the case of pNT was noted above other nitroaromatics taken for study. The binding constant and limit of detection for pNT were calculated to be 1.2 × 105 M−1 and 25 × 10−9M, respectively, using B-H plot. The presence of other nitroaromatics negligibly affects the detection of pNT in CCH solution, as confirmed by anti-interfering studies. FESEM analysis of CCH with pNT confirmed the formation of an adduct. The time resolved fluorescence lifetime measurement also ensured the CCH-pNT adduct formation and the average life time data revealed that the quenching process was dynamic. The CCH-pNT adduct formation was also validated via DFT studies. Overall results suggested that the Schiff base CCH could be an efficient option to detect Cu2+ ions colorimetrically and pNT by fluorimetrically.

An extensive investigation on supramolecular assembly of a drug (MEP) with βCD for innovative applications

Herein, we report the experimental study emerged on the encapsulation of polyether compounds such as mephenesin (MEP) into the nano hydrophobic cage of β-cyclodextrin as host molecule. The commonly known co-precipitation method was followed to prepare inclusion complex (IC) by molar ratio 1:1. Different spectrometric techniques e.g. transform infrared spectroscopy (FTIR), DSC, TGA, DTA and scanning electron microscope (SEM) indicated molecular interactions between β-CD and MEP. UV–visible titration predicts the binding constant for βCD and MEP in solution state around 2.1 × 103 M−1. The formation of the inclusion complex has been predicted by slight shifts in the FTIR as well as 1H NMR spectrum. Job plot and ESI-MS spectra showed that 1:1 inclusion complex has been formed. Molecular docking study unveils the inclusion mechanism which is well supported with the experimental data. In addition, UV–visible spectroscopic study predicts the binding interaction between mephenesin with amino acid residues of BSA and DNA.

Chalcone-based fluorescent chemosensors as new tools for detecting Cu2+ ions

The design and full characterization of new fluorescent chemosensors for Cu2+ is herein presented. The structure of the sensors is based on a chalcone backbone as the chromophoric unit, with di-(2-picolyl)amine (DPA) as a receptor moiety. Two systems, bearing one or two chalcone-DPA units, were synthesized and fully characterized.UV–Vis titrations with several metal ions were performed and both chemosensors exhibited a strong hypsochromic shift in the absorption spectra upon Cu2+ addition, indicating a higher selectivity for this metal over other divalent cations. Additionally, fluorescent spectra recorded in the same conditions revealed a stronger quenching effect in the presence of Cu2+, even in the presence of other metal cations, with association constants above 106 M−1 and detection limits below the micromolar level for both chemosensors. Paper test-strips with one of the chemosensors were prepared to attest its possible application for detecting copper in aqueous samples.

2-((E)-1-((E)-(2-methoxybenzylidene)hydrazono)ethyl)phenol based cost-effective sensor for the selective detection of Eu3+ ions

The detection of lanthanides has emerged as an attractive field of research due to potential applications in biomedical sciences. Here we design a simple and cost-effective ligand 2-((E)-1-((E)-(2-methoxybenzylidene)hydrazono)ethyl)phenol (MHEP) that acts as a rapid selective sensor for Eu3+ ions with a blue shift in UV–visible, ratiometric enhancement in fluorescence intensity and significant redox potential changes in cyclic voltammetric graph among various metal ions in the CH3OH:H2O (1:1, v/v) solvent system. The UV–visible titrations are used to determine the limit of detection 1.2 × 10−7 M, the limit of quantitation 41 × 10−7 M and linear range 22 × 10−6 M−1 to 124 × 10−6 M−1 are determined. The binding stoichiometry is determined by Job’s plot, mole ratio method and Benesi-Hildebrand plot that is found 1:1 (MHEP:Eu3+) with association constant 2.360 × 105 M−1. The IR spectroscopy reveals the role of imine functionalities for the Eu3+ ions detection.

Chromogenic detection of fluoride, dihydrogen phosphate, and arsenite anions based on 2,4-dinitrophenyl hydrazine receptors: spectral and electrochemical study

ABSTRACT The colorimetric recognition of biologically relevant fluoride (F−), acetate (AcO−), and dihydrogen phosphate (H2PO4 −) ions, and poisonous arsenite (AsO2 −) ions, was devised and new receptors for these anions synthesised via the Schiff base condensation procedure. UV–visible titration, fluorescence titration, 1H-NMR titration, and cyclic voltammetry were used to explore the interactions of receptors R1–R3 with anions and possible detection mechanisms. The synthesised probes could sense inorganic fluoride, acetate, dihydrogen phosphate, and arsenite in the organo–aqueous medium (H2O/ Dimethylsulphoxide, 1: 9, v/v) and displayed a change in colour detectable to the naked eye. Out of the three synthesised receptors, receptor R1 showed better sensing ability of fluoride, acetate, dihydrogen phosphate, and arsenite ions in the organo–aqueous medium with a lower detection limit of 0.1 ppm, 0.171 ppm, 0.194 ppm, and 0.144 ppm, respectively. All three receptors formed complexes with the anions through H-bonding interaction followed by deprotonation of the NH proton.

Trivalent Cations Detection of Magnetic-Sensitive Microcapsules by Controlled-Release Fluorescence Off-On Sensor.

A pyrene-based derivative, 2-((pyrene-1-ylmethylene)amino)ethanol (PE) nanoparticle, was encapsulated via water-in-oil-in-water (W/O/W) double emulsion with the solvent evaporation method by one-pot reaction and utilized as a fluorescence turn-on sensor for detecting Fe3+, Cr3+, and Al3+ ions. Magnetic nanoparticles (MNPs) embedded in polycaprolactone (PCL) were used as the magnetic-sensitive polyelectrolyte microcapsule-triggered elements in the construction of the polymer matrix. The microcapsules were characterized by ultraviolet–visible (UV–Vis) and photoluminescence (PL) titrations, quantum yield (Φf) calculations, 1H nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), and superconducting quantum interference device magnetometry (SQUID) studies. This novel responsive release of the microcapsule fluorescence of the turn-on sensor for detecting trivalent cations was due to the compound PE and the MNPs being incorporated well within the whole system, and an effective thermal and kinetic energy transfer between the core and shell structure efficiently occurred in the externally oscillating magnetic field. The magnetic-sensitive fluorescence turn-on microcapsules show potential for effective metal ion sensing in environmental monitoring and even biomedical applications. Under the optimal controlled-release probe fluorescence conditions with high-frequency magnetic field treatment, the limit of detection (LOD) reached 1.574–2.860 μM and recoveries ranged from 94.7–99.4% for those metals in tap water.

Strong Periodic Tendency of Trivalent Lanthanides Coordinated with a Phenanthroline-Based Ligand: Cascade Countercurrent Extraction, Spectroscopy, and Crystallography.

Phenanthroline-diamide ligands have been reported in the selective separation of actinides over Eu(III); on the contrary, relevant basic coordination chemistry studies are still limited, and extraction under actual application conditions is rarely involved. In this work, N,N'-diethyl-N,N'-ditolyl-2,9-diamide-1,10-phenanthroline [Et-Tol-DAPhen (L)] was applied to explore the coordination performance of lanthanides in simulative high-level liquid waste. For the first time, cascade countercurrent extraction was conducted with Et-Tol-DAPhen as the extractant, which reveals the periodic tendency of the extraction efficiency of lanthanides to decrease gradually as the atomic number increases. Comparison of elements with similar radii verifies the hypothesis that the increase in the atomic number leads to a decrease in the ionic radius, thus reducing the coordination and extraction capacity of ligands. Slope analysis, electrospray ionization mass spectrometry, and ultraviolet-visible titration results show that the ligand forms 1:1 and 1:2 complexes with lanthanides and the coordination ability follows the tendency of extraction efficiency, and the first crystal structures of Lns(III) with a phenanthroline-diamide ligand, i.e., [LaL(NO3)3(H2O)] and [LaL2(NO3)2][(NO3)], were obtained, which confirms the conclusions described above. This work promises to enhance our comprehension of the chemical properties of Lns(III) and offer new clues for the design and synthesis of novel separation ligands.

Tuning biological activity in dinuclear Cu (II) complexes derived from pyrazine ligands: Structure, magnetism, catecholase, antimicrobial, antibiofilm, and antibreast cancer activity

In a thrust to establish a structure–activity relationship of dinuclear Cu (II) complexes for derived biological activities, two complexes bearing composition [Cu2(pza)2(2‐methoxybenzoate)4] (1) and [Cu2(pza)2(3‐methoxybenzoate)4] (2) are designed. The complexes are characterized thoroughly via single crystal X‐ray diffraction (XRD), spectroscopic, and magnetic analysis. The exact structure of complexes was elucidated as dinuclear bridged by carboxylates with Cu (II) in each complex present in a distorted square‐pyramidal geometry. The ortho and meta substituted benzoates are used in order to investigate its effect on catecholase and other biological activities. The magnetic data on variable temperature dispense the presence of moderate antiferromagnetic interactions in both the complexes with J = −88.7(2) cm−1, R = 2.13 × 10−4 for 1 and J = −86.3(2) cm−1, R = 3.11 × 10−4 for 2 (g = 2.0). As corroborated from UV–visible titrations, cyclic voltammetry (CV), and Electron paramagnetic resonance (EPR) data, the 2 shows enhanced catecholase activity due to higher redox‐active Cu (II) center in 2, which is directly related to the inductive effect of the methoxy substituent. Both the complexes were screened against some bacteria and fungi, and 2 has shown potent activity Escherichia coli. Moreover, the complexes have also shown better antibiofilm properties as compared to their parent salts. The excellent antibreast cancer activity has been observed against MCF‐7 cell line and, 2has greater IC50 (lower activity) than 1. Thus, a structure–activity relationship can further direct us to design other substituted complexes with enhanced biological activity in the future course.

Electrochromic and bipolar memory switching properties of novel Eu(III)-polymer of multidentate Schiff’s base ligand

In the past thirty years, scientists have put enormous efforts into developing smart materials with multiple functionalities. Among such existing intelligent materials, electrochromic and non-volatile memory materials synthesized via organic–metallic hybrid polymers have shown their remarkable presence. To date, a wide variety of transition metal ions have been adopted for forming these polymers. However, reports on the use of lanthanide metal ion for observing such smart behaviour are uncommon. Therefore, the present report focuses on synthesizing a novel Eu(III) metal ion-based organic–metallic hybrid polymer for observing the smart properties using previously reported Schiff’s base polydentate organic ligand. Further, its different possible coordination modes with the ligand have been discussed. The structure of the polymer has been fully supported by Nuclear Magnetic Resonance and Ultraviolet–visible titration. Along with this, the reversible redox properties of this polymer have also been established along with the study of their spectroelectrochemical properties between yellow and bleached colour. The Resistive Random Access Memory properties of this polymer have been observed by spin coating polymer on Indium Tin Oxide coated substrate for fabricating a Metal–Insulator–Metal structure. The bipolar Current–Voltage (I–V) characteristics of this polymer in both the biasing directions have been observed, with the repeatability of about 1000 cycles for Write-Read-Erase-Read operation. The retention capability of this polymer has also been established for 2000 pulses. Thus, the current work presents fascinating aspects of using a lanthanide metal ion collectively for studying both the redox-active properties, i.e. electrochromic and non-volatile memristive properties.

Colorimetric recognition of multiple first-row transition metals: A single water-soluble chemosensor in acidic and basic conditions

A new tripodal chemosensor named PoPAP for colorimetric-enhancing detection of four metal ions from first-row transition series by combining pyridyl and phenolic binding sites with a highly conjugated pyridinyl-1,3,4-oxadiazolyl-phenyl moiety was designed, synthetized, and structurally analyzed. The chemosensor PoPAP is highly water soluble, it gives a selective fast colorimetric response to cations of iron, vanadium, copper and cobalt, depending on pH conditions, and it can discriminate among different oxidation states. PoPAP sensing ability was explored by absorbance spectroscopic studies, “naked-eye” perception, and UV–visible titration. The chemosensor-metal ions binding constants (Ka) and stoichiometry of host-guest complex in aqueous media were determined by classical analytical methods based on UV–visible data. The coordination geometry of PoPAP copper (II) complex was elucidated by crystal structure analysis and used as starting point for ab-initio calculations to analyze the interaction between ligand and metal.

A ‘one–tube’ synthesis of a selective fluorescence ‘turn off/on’ DNA probe based on a C-phycocyanin-graphene oxide (CPC-GO) bio composite

A naturally fluorescent protein, C-phycocyanin (CPC), was used as a fluorophore to study the effect of graphene oxide (GO) as a quencher. The protein was purified using established procedures and titrated with increasing GO concentrations. UV–visible titration showed a minor effect on the phycocyanobilin absorbance but significant interactions with the amino acid backbone. Fluorescence titration showed notable CPC quenching upon increasing GO concentration to 30 μg ml−1; the corresponding fluorescence dropped by ~97%. A non–linear Stern Volmer curve showed that the fluorophores did not interact directly with the quencher. Powder X-ray diffraction studies showed that the bio-composite lost the crystalline arrangement of GO and became amorphous, akin to CPC. SEM analysis showed GO sheets enfolding a protein nucleus with an increase in oxygen after the interaction compared to CPC. A 20 min incubation of the bio-composite with various biomolecules including amino acids, sugars, polydispersed exopolysaccharides (EPS), other proteins and DNA showed that only DNA could recover the CPC fluorescence. The ‘turn on’ effect of DNA was distinguishable even when all the other molecules were in the same sample matrix. These results showed that CPC GO could be a fluorescence ‘turn off/on’ DNA probe.

A natural cyanobacterial protein C-phycoerythrin as an HS- selective optical probe in aqueous systems.

A naturally fluorescent cyanobacterial protein C-phycoerythrin (CPE) was investigated as a fluorescent probe for biologically and environmentally important hydrosulphide (HS-) ion. It was selective for HS amongst a large anion screen and the optical response was rapid. Sequential UV-visible titration showed considerable peak shift and attenuation with increasing [HS-] while fluorescence titration proved that HS- quenched CPE fluorescence in a concentration dependent manner. The linear response range was 0-2mM HS- while the Stern Volmer curve was non-linear and the limit of detection was 185.12μM. Except bicarbonate and glycine, no anion or biomolecule interfered with the detection even at 10 times the concentration of HS-. It was also free of influences from other sulphur forms like sulphite, sulphate and thiosulphate. CPE reliably detected HS- in freshwater and effluent samples, though some under- and over - estimation was evident. The % recovery ranged from ~96 to 105% (RSD~0.035-0.188%). FTIR analysis showed significant changes in the amide I and II regions of CPE, along with minor modifications in the amide III region as well, showing that HS- was able to influence the protein secondary structure at higher concentrations.

Mercury (II) sensing via cyclization of a dithioamide into a benzimidazole derivative: A structural and spectroscopic study

An o-phenylenediamine-derived dithioamide L was found to sense Hg(II) in the UV–visible via Hg(II)-mediated cyclization leading to a new benzimidazole derivative (L′). Both L and L′ have been characterized by single-crystal X-ray crystallography. The structure of L reveals relatively strong intramolecular H-bonding interactions of NH...S type. The extended structure is consolidated by several classical hydrogen bonding interactions. For L′, analysis of the packing pattern reveals few non-classical H-bonding contacts. Spectroscopic studies by FT-IR, UV–Visible, 1H-and 13C NMR support the single-crystal X-ray crystallography results and confirm the formation of the new benzimidazole derivative. UV–Vis titrations suggest and NMR confirms that the cyclization reaction occurs via an initial formation of a Hg(II) complex, which is too transient to be fully characterized. As this reaction is Hg(II)-mediated, dithioamide L acts as a selective Hg(II) sensor as shown by UV–Visible titrations and a selectivity study against Pb(II), Cd(II), Ca(II), Zn(II), Ag(I), and Cr(III): For Hg(II), but not for other metals, a distinct color change from yellow to pink is observed with corresponding UV–Vis spectroscopic changes and an isosbestic point at 270 nm.