Benesi-Hildebrand Equation Research Articles

Dual-mode strategy for glyphosate detection: Leveraging competitive interaction with iron and zinc-organic frameworks

The extensive use of glyphosate poses a potential threat to food safety, human health, and the ecological environment. Hence, detecting glyphosate residues in food is of great significance for food safety. In this work, the synthesis of zinc-organic frameworks (Zn-MOFs) was achieved through the coordination of Zn2+ with the 2,5-dihydroxyterephthalic acid (DOBDC) ligand. Upon excitation at 350 nm, these Zn-MOFs exhibited robust fluorescence emission at 533 nm. However, upon the addition of iron ions, the Zn-MOFs structure disintegrated, forming a blue Fe-DOBDC complex, resulting in fluorescence quenching. In the presence of glyphosate, the iron ions were chelated by glyphosate, causing the system to lighten in color and restore fluorescence. Further, the mechanism of this strategy was investigated, which was achieved by utilizing the competitive interaction of glyphosate and Zn-MOFs for iron ions. The binding stoichiometry and binding constant of glyphosate:Fe3+ are 1:1 and 7.59 × 103 M−1 using the Job's plot and Benesi-Hildebrand equation, respectively. To enhance glyphosate detection, this study introduced an ingenious dual-mode strategy. By analyzing the colorimetric and fluorescence changes before and after glyphosate addition, we can accurately determine its concentration in the system. The combined colorimetric and fluorescent modalities offer improved reliability and applicability, boasting simplicity, rapidity, and cost-effectiveness. This innovative method is anticipated to find widespread applications and offers novel perspectives on pesticide detection platforms based on ligand competition effects.

A simple and highly selective chalcone fluorescent chemical sensor for the detection of tryptophane

In this study, 1-ferrocenyl-3-(2-hydroxyphenyl) allyl ketone (probe A) was synthesized using a solvent-free method in conjunction with solid-phase grinding and employed as a probe for the detection of tryptophan (Trp). The probe exhibits selective recognition of Trp as evidenced by UV–Vis and fluorescence spectra. In complex scenarios, the probe’s recognition of Trp remains unaffected by both the presence of interfering substances and the duration of exposure. A pH range of 8 to 12 is found to be optimal for the detection of Trp. Job’s curve analysis revealed that the binding ratio between the probe and Trp is 1:1. Based on the Benesi-Hildebrand equation, the binding constant for the interaction between probe A and Trp is calculated to be 1.5 × 107 M−1. The detection limit for Trp was determined to be 9.55 × 10−5 M. The sensing mechanism of the probe for Trp was elucidated through 1H NMR and FT-IR analyses.

A New Proton Transfer Complex Between 3,4-Diaminopyridine Drug and 2,6-Dichloro-4-nitrophenol: Synthesis, Spectroscopic Characterization, DFT Studies, DNA Binding Analysis, and Antitumor Activity.

The proton transfer (PT) complexation reaction between 3,4-diaminopyridine (3,4-DAP), an important drug, and 2,6-dichloro-4-nitrphenole (DCNP) was investigated experimentally and theoretically. The experimental results indicated a chemical reaction occurred because of a hydrogen bonding, followed by proton transfer from the DCNP to the 3,4-DAP in different polar media. The Benesi-Hildebrand equation was used to estimate the formation constant (Kf), molar absorptivity (εPT), and other physical parameters. The formed PT complex was characterized using FTIR, 1H, and 13C NMR spectra. In addition, the nanocrystalline structure, particle sizes, and surface morphology of the complex were investigated by XRD and SEM-EDX. The structure of the 1:1 PT complex was calculated theoretically in the gas phase and the presence of solvent effects. Using TD-DFT calculations, the band observed at 406 nm (Calc. 379.5 nm) and 275 nm (Calc. 272.3 nm) could be assigned to the HOMO→LUMO transition (99%), and HOMO→L+3 transition (87%), respectively. The DNA binding ability of the PT complex was investigated, revealing an intercalative binding mechanism with a binding constant Kb of 4.6 × 104 M-1. Based on the results of the Ct-DNA binding study, the binding free energy of the PT complex with the receptor of human DNA (PDB ID:1BNA) is found to be -7.2 kcal/mol. The cytotoxic effects of the PT complex were evaluated on selected cancer cell lines, demonstrating significant antitumor activity against A-549 and MCF-7 cancer cell lines.

Charge Transfer Interaction Dynamics between 2-Methyl-8-hydroxyquinoline and 2,4-Dinitrophenol: Synthesis, Spectroscopic Characterization, DNA Binding and DFT Studies

A novel charge transfer (CT) complex was formed by combining the electron-acceptor 2,4-dinitrophenol (DNP) with the electron-donor 2-methyl-8-hydroxyquinoline (MHQ). The complex obtained was further characterized using both experimental and theoretical methods. The Benesi-Hildebrand equation can be utilized to determine various spectroscopic physical measurements such as the molar absorptivity (εCT) and formation constant (KCT). The CT complex has a stoichiometry of 1:1. Multiple spectroscopic methods were employed to investigate the resultant solid compound. The existence of charge and proton transfer in the resultant complex was confirmed by FT-IR, 1H NMR, SEM-EDX and powder-XRD studies. An electron absorption spectroscopy examination was done to analyze the complex DNA binding capability. The resulting complex was determined to have an intercalative binding mechanism, with an intrinsic binding constant (Kb) value of 4.2 × 106 M-1. The experimental results were corroborated by performing theoretical calculations using DFT using a CAM-B3LYP/6-31G(d,p) basis set. The geometrical parameters, electrostatic potential maps (MEPs) and Mullikan charges were computed and examined in agreement with the experimental observations. In addition to electron transmission, the stability of the complex is influenced by the presence of a hydrogen bond.

Synthesis of Ferrocenyl Chalcone-Containing Aminourea Schiff Bases and Their Detection on Tryptophan.

In this paper, 1-phenyl-3-ferrocenylenone aminourea Schiff bases were synthesized by a novel method. A multifunctional molecular probe (Probe A) of 1-phenyl-3-ferrocenylenone, carbon-based solid acid, aminourea, and anhydrous ethanol was synthesized by adding them to a vessel at elevated temperatures and refluxing for the synthesis of a multifunctional molecular probe (Probe A) of 1-phenyl-3-ferrocenylenone aminourea Schiff base, and it was found that it recognizes tryptophan (Trp) in solution, and that the catalyst can be reused more than five times after recycling. This method is characterised by low cost, high efficiency, green environment and no waste acid. Fluorescence and UV spectra show that probe A specifically recognizes tryptophan (Trp) without interference by other amino acids or pH and time does not affect it within 45min. The lowest limit of detection for Trp was 1.307 × 10- 4 mol/L for probe A. The binding ratios of probe A to Trp were measured to be 1:1 by Job's plotting method, respectively. The complexation constant of probe A with Trp was found to be 2.733 × 107 L/mol according to the Benesi-Hildebrand equation. The bonding mechanism was explored through IR spectroscopy and ¹H NMR titration.

Assessing the structural, antibacterial, and dissolution properties of 1:1 doxycycline/β-cyclodextrin complexes

A 1:1 β-cyclodextrin (βCD) inclusion complex with doxycycline (DO) as the guest molecule was prepared using kneading (KN) and coprecipitation (CoP) methods, along with a physical mixture (PM) . The complex was characterized through FTIR, ¹H NMR, UV–Vis spectroscopy, and DSC analysis. Semi-empirical quantum mechanical calculations confirmed the inclusion of DO within βCD's hydrophobic cavity. The formation constant, determined by a modified Benesi-Hildebrand equation at 25 °C, was 116.22 M⁻¹ for the βCD-DO complex. Dissolution studies revealed that the CoP method significantly enhanced DO's dissolution kinetics compared to the KN, PM methods, and free DO, highlighting CoP's effectiveness. Molecular docking indicated a stable βCD-DO complex, with binding energies from -5.9570 to -6.1423 kcal/mol, driven by hydrophilic and hydrophobic interactions. Antibacterial testing against E. coli, P. aeruginosa, S. aureus, B. cereus, and B. subtilis showed CoP had the highest efficacy, with MIC values of 5–10 µg/ml and MBC values of 10–20 µg/ml, better than KN, DO, and βCD.

Spectrophotometric analysis and mechanistic insights investigation of a developed CT complex as colorimetric real-time sensing performance towards Fe2+ in aqueous medium

A newly developed charge transfer complex (CTC) is explored for colorimetric real-time sensing behavior towards the Fe2+ ion, as a highly selective real-time colorimetric chemosensor material. The synthesized and characterized CTC / P1, [(2HP)+(SA)−] is cheap, remarkably distinctive, and simple to manufacture. Beyond the exposure limitations, iron is also the most common cofactor in enzyme reactions, which is, therefore a crucial part of life. However, too much or not enough iron leads to anemia, liver damage, cancer, Alzheimer's disease, and Parkinson's disease. In this report, unusual sensing capacity has been reported with a relatively low detection limit of 1.247 ppb for Fe2+ ions in aqueous medium, which was lowest at 1.267 ppb in previous reports of CTC sensors. By using a static quenching process, the incredible sensing behavior of this material as a chemosensor was determined. Colorimetric sensing behavior in real-time has also been observed. The complex has been described using a variety of methods, including UV-visible and FTIR spectroscopy. In FTIR spectra, the CTC (P1) showed a change in wavenumber when compared to its reactants. Furthermore, the complex's stoichiometry was measured using UV-visible spectroscopy by taking mixture with an equimolar ratio using the straight-line approach known as the Benesi-Hildebrand equation, which was found to be 1:1. Oscillator strength (f), transition dipole moment (μEN), molar extinction coefficient (εCT), energy of interaction (ECT), and stability constant (KCT) were among the thermodynamic and physical characteristics studied. Van't Hoff's equation was used to compute other parameters such as Gibbs free energy (G°), absorptivity coefficient (ε), Resonance energy (RN), etc. [O+—H……O−] hydrogen bonding was used to depict the interaction between reactants (salicylic acid and 2-hydroxypyridine). The stability of the P1 as a function of temperature is demonstrated through TG/DTA analysis.

A specific ‘Turn-on’ fluorogenic probe for the detection of phosphate ions

Phosphate (PO43-) ions are an essential trace element in the human body and play a vital role in biological and ecological systems. However, excess consumption of PO43- ions causes various serious health issues and becomes hazardous to public safety. Thus, selective tracking and quantification of PO43- ions is a significant concern to the scientific communities. In the present article, we have introduced a chromo-fluorogenic probe APES, which instantly shows a characteristic color-fluorimetric change towards PO43- ions. APES shows an instant greenish-yellow fluorescence at 530 nm and a yellow to orange naked-eye visible colorimetric change in the presence of PO43- ions. The detection and quantification limit of PO43- ions employing APES is estimated as 1.5 µM and 5.0 µM respectively. The interaction affinity of APES towards PO43- ions is found by the Benesi-Hildebrand equation as 0.42 × 105 M-2 in a 20 % water-DMSO medium. Also, our modeled probe is biologically significant as it can detect and quantify PO43- ions within the range of 50 % water medium. A super handy paper-strips-based detection tool has also been fabricated utilizing APES which could be employed to track trace amounts of PO43- ions. The mechanism involved in the detection of PO43- ions is elucidated through 1H NMR and density functional theoretical analysis. Also to deeply entrust the selectivity with quantification capability and practical usability of our probe APES, a real sample analysis is performed to explore the fruitful real-time analysis by experimenting with different sources of water.

The Binding Mechanism Between Cyclodextrins and Anticancer Drug Noscapine: A Spectroscopic and Molecular Docking Study.

In this paper the binding of noscapine (NOS) as an anticancer drug with poor bioavailability and low solubility with beta and methyl-beta cyclodextrins (β-CD and M-β-CD) as the biocompatible drug carriers were discussed using ultraviolet-visible, fluorescence and nuclear magnetic resonance spectroscopy, as well as molecular docking. The absorption of NOS changed when it was bound to both cyclodextrins, resulting in a hyperchromic shift. It formed a 1:1 stoichiometry inclusion complex with both cyclodextrins according to the Benesi-Hildebrand equation. The binding affinity was larger in NOS-M-β-CD (5.9 (± 0.66) × 103 M- 1) than NOS-β-CD (3.7 (± 0.22) × 103 M- 1) complex. The fluorescence emission band of NOS at 408nm was quenched when NOS was complexed with β-CD, and enhanced in the presence of M-β-CD, while the shoulder at 350nm was enhanced selectively when NOS was complexed with M-β-CD. The fluorescence quenching of NOS with β-CD showed a negative deviation from the Stern-Volmer. The thermodynamic parameters have been estimated with the help of the Van't Hoff equation in different temperatures, and a dynamic mechanism was proposed for quenching. Also, both ΔH and ΔS have positive values thus the main interactions result in hydrophobic forces. Moreover, the negative value of ΔG indicates that the bonding process is spontaneous. 1H NMR chemical shift changes were observable for NOS and both CDs protons due to the chemical environment changes of some nuclei upon complexation. The molecular docking results revealed that the 1:1 inclusion complex possesses a good molecular shape complementarity score for their most probable structures, and indicated that the M-β-CD inclusion system gave the higher complexation efficiency. The binding energy values for β-CD and M-β-CD were determined to be -6.7 and - 9.5kcal/mol, respectively. These findings suggest the same as the result of experimental tests that the NOS-M-β-CD complex is more stable than the NOS-β-CD complex.

Polymer and micellar catalysis in d-fructose oxidation by imidazolium fluorochromate: A kinetic and mechanistic study

This work investigated the oxidation of d-fructose using imidazolium fluorochromate (IFC) as an oxidant and analyzed how sodium dodecyl sulfate (SDS) and polyethylene glycol (PEG-400) affected the reaction kinetics. The process exhibited a unit-order dependence on IFC, d-fructose, and perchloric acid concentration. Perchloric acid was the primary source of hydrogen ions in the reaction mixture. The stoichiometry of the reaction indicated that 3 mol of d-fructose requires 4 mol of IFC. Acrylonitrile, a radical-generating species, did not impact the reaction rate, indicating the absence of a free radical intermediate. The reaction rate decreases as the Mn (II) ions concentration increases, suggesting the involvement of Cr (IV) species in the reaction. The dielectric value of the reaction medium (D) had an inverse effect on the rate, and the outcomes were consistent with the Amis (log k1 and 1/D) and Kirkwood plots (log k1 and (D-1/2D+1)), indicating the presence of dipole-dipole interactions in the process. SDS and PEG-400 catalyzed the reaction. The reaction showed significant catalysis before reaching the critical micelle concentration (CMC). However, the observed rate constants stabilized at higher SDS concentrations exceeding the CMC. Piszkiewicz's cooperativity model was employed to describe the surfactant catalysis, while the Benesi-Hildebrand equation was utilized to explain polymer catalysis. The activation parameters are ΔH† = 44.3 ± 1.3 kJ mol−1, and ΔS† = −133.4 ± 4.3 J K−1 mol−1. The products of the reaction have been identified by spectral analysis as d-arabinoniclactone and formic acid. The formation of an ester complex followed by its decomposition was proposed as the rate-limiting step in the proposed mechanistic reaction pathway.

Chinese food seasoning derived carbon dots for highly selective detection of Fe3+ and smartphone-based dual-color fluorescence ratiometric visualization sensing

Carbon dots were obtained from Tangshai, a Chinese food seasoning, using a simple and green method through dialysis. Tangshai-derived carbon dots (TSCD) exhibited unique fluorescent emission properties that can be selectively suppressed by Fe3+ over other heavy metal ions including Fe2+. Based on the Benesi-Hildebrand equations study, a ten times larger coordination constant of Fe3+-TSCD than that of Fe2+-TSCD was obtained, which proved the highly selective superiority. Therefore, a fluorescence quenching method for sensitive detection of Fe3+ was established with two linear ranges of 1–80 µmol L−1 and 200–500 µmol L−1 and the limit of detection (LOD) was 0.41 µmol L−1 (3σ). The real sample detection was performed with satisfactory and validated results. Besides, coupled with orange emissive carbon dots (OCD) whose fluorescence can be enhanced by Fe3+, a dual-color fluorescence ratiometric sensor for Fe3+ was established from the opposite fluorescence responses, and visualization sensing was actuated by a smartphone. This work facilely extracted CDs from Chinese food seasoning and revealed the mechanism of selective sensing for Fe3+, facilitating the green synthesis of CDs and heavy metal ions sensing.

Charge transfer interaction dynamics between 6-Aminoindole and picric acid: Synthesis, spectrophotometric, characterization, computational, DNA binding, and anticancer properties

The charge transfer complex (CT) chemistry is studied between electron donor 6-Aminoindole (AMI) and electron acceptor Picric acid (PA) at 25 °C, in an acetonitrile medium by using UV–Visible absorption spectroscopy. The molecular ratio of the CT complex was determined to be 1:1 by using jobs variation and spectrophotometric titration processes. To assess the stability constant (KCT), and molar extinction coefficient (ƐCT) by using the Benesi-Hildebrand equation. These outcomes reveal that the synthesized CT complex is highly stable. The thermodynamic study is carried out in different temperatures (20-45 °C), and these results indicate increases the stability with increasing temperature. The CT complex structure was analyzed by FT-IR, 1H NMR, and 13C NMR. The surface morphology and elemental composition were identified by the SEM-EDX technique. The crystalline nature was analyzed by powdered XRD investigation. The CT complex has been screened for DNA binding and invitro cytotoxicity. The DNA binding constant value (2.3 × 105 M−1) and in vitro cytotoxicity test results on HeLa, suggest that it could be used as a potential medicinal drug in the future. Finally, the geometry optimizations were carried out by the DFT with the wB97XD method and 6-31+G(d,p) basis set. Here we investigated different parameters like bond parameters, NBO analysis, FMO analysis, DOS, PDOS, and computed electronic spectra. The computational analysis provided additional support for the experimental CT complex formation.

π‐Conjugated polyfluorenes with o‐phenylenediamine unit: Synthesis, optical and electrochemical properties, charge transfer complexation, and DNA sensing

Abstractπ‐Conjugated polyfluorenes (PPs) comprising 2,3‐diaminobenzene‐1,4‐diyl (unit A) and 9,9‐dihexylfluorene‐2,7‐diyl (polymer‐1) or 9,9‐bis(6‐N,N,N,‐trimethylammoniumhexyl)fluorene‐2,7‐diyl (unit B) (polymer‐2) units were synthesized using Suzuki‐Miyaura coupling polycondensation. To compare the chemical properties and functionality of polymer‐2, a water‐soluble PP comprising benzene‐1,4‐diyl and unit B (polymer‐3) was synthesized. Polymer‐1 exhibited solvatochromism: the photoluminescence (PL) peak of the polymer in solutions shifted to a longer wavelength with an increase in the dielectric constants of solvents. Polymer‐1 formed charge transfer (CT) complexes with organic electron acceptors. The CT complexation behavior was systematically elucidated by the PL measurements using Stern–Volmer and Benesi–Hildebrand methods. Water‐soluble polymer‐2 could be used as a sensor for the chain length of telomere DNA by monitoring the changes in its PL intensity upon the addition of the analyte. The DNA sensing performance of polymer‐2 surpassed that of polymer‐3, attributed to the presence of unit A in polymer‐2. This unit brought polymer‐2 closer to DNA through hydrogen bonding between the amino group of polymer‐2 and nucleic acids in DNA. This interaction facilitated the occurrence of CT from the polymer backbone to DNA.

Determination of Binding Constants for the Complexes Between Heavy Metal Ions and Cucurbit[n]uril

AbstractOne of the major concerns worldwide is the rapid increase in water pollution with hazardous heavy metals. The Cucurbit[n]uril (CB[n]) structure provides an inner hydrophobic cavity accessible through two electrostatically negative portals with polar carbonyl groups, allowing for charged ion–dipole interaction between cationic species with excellent binding affinities. In this work we selected CB[5], and CB[7] for the titrimetric and electrochemical evaluation of the heavy metal complexes formed with Copper(II), Cadmium(II) and Lead(II). The host–guest interaction was found by either attenuation of the redox peaks, the formation of a new peak, or the slight shift in the redox peaks of the heavy metal ions. Titration data were obtained for CB[n] with the heavy metal solutions to determine the molar coefficient of binding. The stoichiometry of the complexes was 1 : 1 by Job′s plot. We calculated the binding constants using the Benesi–Hildebrand method achieving relatively good binding constants (K) ranging from (1.80±0.14)×105–(4.98±0.13)×105 M−1. The results showed that the complexes of Cadmium(II) and Lead(II) with both CB[5] and CB[7] are highly stable in aqueous media. Copper(II) was able to bind to the smaller sized portal of CB[5], whereas with CB[7] the heavy metal ion could not form a favourable complex. This phenomenon suggests that the CB[5] is an ideal host at forming stable host–guest interactions than their larger homologue.

Phase separation, aggregation, and complexation of triton-X100 and bovine serum albumin mixture: A combined cloud point and UV–visible spectroscopic approaches

Phase separation and aggregation behaviour of triton X-100 (TX-100) and bovine serum albumin (BSA) mixture were investigated using cloud point and UV–visible spectroscopic techniques. The effects of various hydrotropes (HYTs) - namely, sodium salicylate (SS), sodium benzoate (SB), glycerol (Glyc), and 4-aminobenzoic acid (4-ABA) - on the cloud point (CP) of TX-100 + BSA were determined. The obtained CP values for the mixed system in the presence of HYTs followed the order:CPH2O+4−ABA<CPH2O+Glyc<CPH2O+SB<CPH2O+SS. The measured critical micellization concentration (CMC) values of the TX-100 + BSA mixture were found to be significantly altered with varying amounts of BSA. The calculated free energy of clouding and micellization indicated the non-spontaneous nature of the phase transition and the spontaneous association of the TX-100 + BSA mixture. The non-spontaneity of phase separation decreased with increasing concentrations of HYTs. The enumerated values of ∆Hco and ∆Sco were consistently recorded as negative and positive magnitudes, respectively, in all aqueous HYTs media. The clouding process occurred due to a combination of hydrophobic and electrostatic interactions. The binding constant of the mixed system was determined employing the UV–vis spectroscopic method using the Benesi-Hildebrand equation.

Colorimetric detection of clotrimazole environmental pollutant using a newly developed chemosensor; an experimental and theoretical study

ABSTRACT Clotrimazole (CTZ), as an antifungal medication, is used to treat dermatological infections in humans, and to remove fungal infections from plants in agriculture, but its widespread usage has led to pharmaceutical pollution and environmental concerns. In this study, a new bromopyrogallol red (BPR) and N i 2 + based colorimetric sensor was developed for the selective and sensitive detection of CTZ. The BPR-Ni complex showed a clear colour change from purple to violet in the presence of CTZ, and a significant change was observed in the UV-Vis spectrum. The stoichiometric ratio of 1:1 between BPR and N i 2 + was determined using the Benesi-Hildebrand method. DFT and time-dependent DFT (TD-DFT) were applied to identify the molecular and electronic structures of the BPR, BPR-Ni, and BPR-Ni-CTZ in ground and excited states. The nature of electronic excitations and charge transfers was evaluated using the natural transition orbitals (NTO). The NTO analysis reveals that the Ni atom facilitates the charge transfer process between BPR and CTZ and improves the sensitivity of the chemosensor. The quantum theory of atoms in molecules (QTAIM) was employed to determine the nature of interactions between BPR, N i 2 + , and CTZ. This study paves the way for the detection of environmentally harmful pharmaceutical pollution using simple but effective colorimetric sensors.

A novel quinoxaline-based multifunctional probe: Sensitive and selective naked-eye detection of Fe3+ and fluorescent sensing of Cu2+ and its application

A new quinoxaline derivative (QM: 6-methyl-2,3-di(quinoline-2-yl)quinoxaline) was synthesized as a colorimetric and fluorescent chemosensor for detecting Fe3+ and Cu2+ ions. QM can selectively detect Fe3+ among a number of essential cations and showed an obvious colorimetric response (colorless to yellow) in the presence of Fe3+ ions and considerable fluorescence quenching response towards Cu2+ ions. The molar ratio and Job plot showed a 1:1 stoichiometric ratio for the QM-Fe3+ and QM-Cu2+ complexes. The binding constants for QM-Fe3+ and QM-Cu2+ were found to be 3.335 × 105 and 2.230 × 103 M−1, respectively, using the Benesi-Hildebrand method. The quenching rate constant (Ksv) for QM-Cu2+ was 18.8 × 103 M−1 using the Stern-Volmer plot. The limits of detection and quantification for QM-Fe3+ were calculated as 0.236 and 0.787 µM, respectively, and those for QM-Cu2+ were 0.39 and 1.31 µM, respectively. Therefore, sensor QM can be used to quantify Fe3+ and Cu2+ ions in real samples with good recovery.

A multifunctional probe based on ferrocenyl chalcone for the detection of tryptophan and ascorbic acid in solution

A multifunctional probe based on ferrocenyl chalcone (Probe M) was designed and successfully synthesized and found to recognize tryptophan (Trp) and ascorbic acid (AA) in solution simultaneously. The minimum detection limit of Probe M for Trp-and AA was 1.3188 × 10−4 mol/L and 1.1545 × 10−4 mol/L, respectively. The binding ratios of Probe M to Trp-and AA were obtained by job plot as 1:1 and 2:1, respectively. According to the Benesi-Hildebrand equation, the complexation constants of Probe M for Trp-and AA were 3.0025 × 106 L/mol and 4.6606 × 106 L/mol, respectively. The binding mechanism was also investigated by IR and NMR titration.

Rhenium(I) complexes incorporating pyrene bearing N, N ligand: Luminescent based sensors for DNA

Biologically active pyrene based rhenium (I) complexes (1–2) were designed as fac-[Re(CO)3LCl], (where L = L1 (E)-N-(quinolin-8-ylmethylene)pyren-4-amine and L2 (E)-N-(pyridin-2-ylmethylene)pyren-4-amine) and structurally characterized by X-ray crystallography, which suggested a distorted octahedral geometry around the metal centre. The complexes were also characterised by various spectroscopic techniques. The binding of the rhenium complexes to CT-DNA was examined by UV–Vis spectroscopy, fluorescence quenching studies with ethidium bromide and viscosity measurements. Between both the complexes, 2 showed a greater binding ability to CT-DNA, as is evident from the numerical value of the binding constant, calculated using the Benesi-Hildebrand equation.

Performance of 4,5-diphenyl-1H-imidazole derived highly selective 'Turn-Off' fluorescent chemosensor for iron(III) ions detection and biological applications.

Two fluorescent chemosensors, denoted as chemosensor 1 and chemosensor 2, were synthesized and subjected to comprehensive characterization using various techniques. The characterization techniques employed were Fourier-transform infrared (FTIR), proton (1 H)- and carbon-13 (13 C)-nuclear magnetic resonance (NMR) spectroscopy, electrospray ionization (ESI) mass spectrometry, and single crystal X-ray diffraction analysis. Chemosensor 1 is composed of a 1H-imidazole core with specific substituents, including a 4-(2-(4,5-c-2-yl)naphthalene-3-yloxy)butoxy)naphthalene-1-yl moiety. However, chemosensor 2 features a 1H-imidazole core with distinct substituents, such as 4-methyl-2-(4,5-diphenyl-1H-imidazole-2-yl)phenoxy)butoxy)-5-methylphenyl. Chemosensor 1 crystallizes in the monoclinic space group C2/c. Both chemosensors 1 and 2 exhibit a discernible fluorescence quenching response selectively toward iron(III) ion (Fe3+ ) at 435 and 390 nm, respectively, in dimethylformamide (DMF) solutions, distinguishing them from other tested cations. This fluorescence quenching is attributed to the established mechanism of chelation quenched fluorescence (CHQF). The binding constants for the formation of the 1 + Fe3+ and 2 + Fe3+ complexes were determined using the modified Benesi-Hildebrand equation, yielding values of approximately 2.2 × 103 and 1.3 × 104 M-1 , respectively. The calculated average fluorescence lifetimes for 1 and 1 + Fe3+ were 2.51 and 1.17 ns, respectively, while for 2 and 2 + Fe3+ , the lifetimes were 1.13 and 0.63 ns, respectively. Additionally, the applicability of chemosensors 1 and 2 in detecting Fe3+ in live cells was demonstrated, with negligible observed cell toxicity.