Benesi-Hildebrand Equation Research Articles

A dual responsive probe based on bromo substituted salicylhydrazone moiety for the colorimetric detection of Cd2+ ions and fluorometric detection of F‒ ions: Applications in live cell imaging

A dual responsive probe based on bromo substituted salicylhydrazone moiety for the colorimetric detection of Cd2+ ions and fluorometric detection of F‒ ions: Applications in live cell imaging

Interaction of cephalexin monohydrate with surfactants in aqueous and sodium chloride solution at variable temperatures: Conductivity and spectroscopic measurements

Cephalexin monohydrate (CLM) is a well-known antibiotic applied for prohibiting bacterial growth. Herein, the mode of interaction of CLM with both ionic (cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS)), and nonionic (triton X-100 (TX-100)) surfactants, was investigated using the conductivity measurement and UV–Visible spectroscopic techniques in H2O and NaCl + H2O media at numerous temperatures ranging from 293.15 to 328.15 K. In the current study, the critical micelle concentration (CMC) of CLM + CTAB and CLM + SDS mixed systems was estimated from a sudden and clear breakpoint of specific conductivity (κ) versus the concentration of surfactant plot. A single CMC was found for both CLM + CTAB and CLM + SDS systems in entirely experimental cases studied. The value of CMC of surfactants undergoes a drop in presence of CLM in an aqueous phase and hence, the drug causes an enhancement of the extent of micellization of surfactants. Also, the CMC values of CLM + CTAB and CLM + SDS mixed systems were found to reduce in NaCl + H2O medium and the CMC values were observed to experience a further reduction with increasing concentration of NaCl salt. A negative standard free energy change (∆Gmo) of micellization discloses that the CLM + ionic surfactant micellization is spontaneous. The different thermodynamic parameters of transfer and the enthalpy-entropy compensation parameters of micelle formation were also measured and demonstrated appropriately. The binding constant (Kb) of the CLM + TX-100 mixture has been evaluated from the Benesi-Hildebrand equation and the values were found to be dependent on CLM concentration and temperature. The ∆Hbo and∆Sbo values of CLM + TX-100 mixture reveal the survival of the electrostatic force of interaction along with the presence of hydrophobic interaction developed between the CLM drug and TX-100 surfactant.

Synthesis of Coumarin Derived Thiosemicarbazones as Colorimetric and Fluorescent 'Turn On' Chemosensors for Fluoride Ions

Chemosensors are getting attention day-by-day owing to their usage as analyte detector for environmental pollutants and in biological imaging. Coumarin based thiosemicarbazones (S1 and S-2) are reported as anionic chemosensors. The structural elucidation of the synthesized chemosensors is done by 1 H-NMR, 13 C-NMR, UV-Visible spectroscopy, and Fluorescence emission spectroscopy. The limit of detection (LOD) for F − ions was determined as 23.33 μM and 16.90 μM while the binding constant was assessed as 4.92 × 10 4 M −1 and 4.84 × 10 4 M −1 for sensor S1 and S2 respectively, based on UV–vis titration using Benesi-Hildebrand equation.

Micellar and Polymer Catalysis in the Kinetics of Oxidation of L-lysine by Permanganate Ion in Perchloric Acid Medium

ABSTRACT Kinetics of oxidation of L-lysine by permanganate ion in a perchloric acid medium was investigated to explore the order of the reaction with respect to oxidant and substrate and to study the catalytic behaviour of sodium lauryl sulphate (SLS) and polyethylene glycol (PEG). The reaction was found to be first-order with respect to the oxidant and the substrate and zero-order with respect to hydrogen ion. Changes in the sodium sulphate concentration produce a non-significant variation in the rate of the reaction. SLS and PEG were found to catalyze the reaction. Surfactant catalysis was modelled by Piszkiewicz's cooperativity model, while polymer catalysis was explained with the help of the Benesi-Hildebrand equation. The temperature dependence of the rate of the reaction was elucidated, and activation parameters were obtained. Interestingly, the reaction was found to possess positive activation entropy indicating the dissociative nature of the transition state and outer-sphere electron transfer mechanism. A mechanism of the reaction that is supported by the experimental findings was suggested. Keywords: L-lysine, permanganate ion, micellar catalysis, polymer catalysis, outer sphere electron transfer mechanism.

α-Substituted phthalocyanines based on metal-induced H- or J-type aggregation for silver and palladium ions: synthesis, fluorescence, and antimicrobial and antioxidant properties.

In this study, firstly, 3-(2,3-bis(hexadecylthio)propoxy)phthalonitrile (2) as a new phthalonitrile derivative was prepared. Then, new types of non-peripheral phthalocyanine derivatives [CuPc (3), ZnPc (4), and CoPc (5)] were synthesized by using this ligand. The synthesized new compounds were characterized by common spectroscopic methods such as FTIR, 1H-NMR, 13C-NMR, MALDI-TOF, UV-Vis and fluorescence spectroscopy. The H- or J-type aggregation behaviors of novel type metallophthalocyanines in the presence of valuable metal ions such as Ag(i) and Pd(ii) were investigated by UV-Vis and fluorescence spectroscopy. The quenching efficiency of the Ag(i) and Pd(ii) ions for ZnPc (4) was obtained using the Stern-Volmer equation and the quenching constant of ZnPc (4) towards Ag(i) and Pd(ii) ions was found to be 2.9 × 105 mol L-1 and 1.2 × 105 mol L-1, respectively. The binding constant (Ka) and binding stoichiometry (n) of Ag(i) and Pd(ii) ions for ZnPc (5) were calculated using a modified Benesi-Hildebrand equation, and were found to be 1.4 × 108 M-1 and 3.4 × 107 M-1, respectively. The binding ratio and free energy change of Ag(i) and Pd(ii) ions for ZnPc (4) were found to be 1.86, 1.54, -46.49 kJ mol-1 and -42.9 kJ mol-1, respectively. Also, the antioxidant properties of the synthesized novel type metallophthalocyanines and their Ag(i) and Pd(ii) ion doped aggregates were determined using three different methods: DPPH free radical scavenging activity, ferrous ion chelating activity and reducing power activity. Finally, the antibacterial and antifungal activities of phthalocyanine compounds synthesized within the scope of this study were determined by disc diffusion and macrobroth dilution methods and the effect of the doping of Ag(i) and Pd(ii) ions on the antibacterial activities of phthalocyanines was investigated.

Novel schiff base synthesis of E-N-(1-(1H-phenothiazin-2yl)-ethylidene)-3-((E)-(2-phenylhydrazono) methyl) aniline “Turn-on” fluorescent chemosensor for sensitivity and selectivity of detection of Cr3+ and Pb2+ ions

Abstract The Synthesized E-N-(1-(1H-phenothiazin-2yl)-ethylidene)-3-((E)-(2-phenylhydrazono)methyl)aniline (AT) was characterized by FT-IR, MS, H1, and C13 spectroscopy instruments. The chemosensor demonstrates fluorescent performance with high sensitivity and selectivity detection of Cr3+ and Pb2+over other coexistent metal ions in 100% aqueous solution, and even with a visual fluorescence change from light yellow to light blue. The probe shows “turn-on” fluorescence intensity at 428 nm (excitation wavelength 290) in HEPES buffer solution in EtOH: H2O (1:4, v/v, pH = 7.0). Significantly, the fluorescence enhancement was attributed to photoinduced electron transfer (PET). The Job plot for showed Cr3+ and Pb2+ complex formation for both metal ions with 1:1 stoichiometry and was predicted at 0.6 μM concentration. Additionally the binding constant was found to be 2.13 × 104 M−1(R2 = 0.9991) and 2.37 × 104 M−1 (R2 = 0.9996) according to Benesi-Hildebrand equation and detection limit at 8.63 × 10−7 M (R2 = 0.9992) and 7.42 × 10−7 M (R2 = 0.9990) and WHO (World Health Organization) allowed (7.4 μM) for drinking water. The pH experiments range from 4 to 10 in sensing application and reversible and irreversible due to EDTA + Cr3+ and EDTA + Pb2+added into AT solution. The theoretical calculation was performed by B3LYP/6–31*G in Gaussian 09 program. The CYGD has strong cytotoxic in-vitro activity against cell line HepG2. We believe that our protocol receptor would be a valuable addition in academia for its optical properties and also excellent practical applications in biomedical industries.

A new N-methylhydrazinecarbothioamide incorporated “naked-eye” and “turn-off” chemosensor for selective and low detection of Cu2+ ions and computation study

The rising concentration of Cu2+ ions in the environment is dangerous and showed adverse effects on the environment and human health. To concern this issue in this work, we designed N-methylhydrazinecarbothioamidebased (E)-2-(2-methoxy-4-(3-(2-methoxy-4-((E)-(2-(methylcarbamothioyl) hydrazono)methyl)phenoxy)propoxy)benzylidene)-N-methylhydrazinecarbothioamide (PMPMMHC) new chemosensor for selective and rapid detection of Cu2+ ions with quenching in luminescence or “turn-off” response among various cations and anions in semi-aqueous medium DMSO/H2O (1/1 v/v). The addition of Cu2+ ions to the solution of PMPMMHC showed remarkable changes in color, UV–vis, fluorescence spectra, and redox potential. The insight spectroscopic titrations result in the binding stoichiometry 1:2 (PMPMMHC:Cu2+) with a limit of detection (LOD) 15 Nm showing good binding constant 1.37 × 107 L2 mol−2 as determined by the Benesi–Hildebrand Equation in the linear range of detection 20–200 μM. In computational studies, chemosensor reveals unique interaction with Cu2+ as a result of metal-pi acceptor (2.33 Å and 2.77 Å) interactions as well as the non-classical intra-hydrogen bonding. In mechanistic studies, the photoinduced electron transfer (PET) inhibits and signal changes arise due to the electronic transition of higher-energy orbitals (HOMO) to lower energy orbitals (LUMO) as a result of PMPMMHC:Cu2+ binding.

A dual probe for selective sensing of Zn (II) by fluorescent and Cu (II) by colorimetric methods in different systems based on 7,8-benzochromone-3-carbaldehyde -(fluorescein)hydrazone

In this study, a novel fluorescent probe sensor, 7,8-benzochromone-3-carbaldehyde (fluorescein)hydrazone L, was designed and synthesized. Based on the photoinduced electron transfer (PET) process, L can detect Zn2+ in the solution of EtOH/H2O (9/1, V/V). The probe had high selectivity and sensitivity to Zn2+ with a lower detection limit of 3.4 × 10−7 M. Furthermore, the coordination ratio of L-Zn2+ was 1:1, which could be corroborated by Job’s plot. In addition, in the EtOH/ H2O (5/2, V/V) solution of the probe L, Cu2+ was added to produce a marked change in color from achromatous to yellow, indicating that the probe L could detect Cu2+ by colorimetry, which was detectable by the naked eye, simply and quickly. According to the Benesi-Hildebrand equation, the complexing constants values of L-Zn2+ and L-Cu2+ were 9.8 × 104 M-1 and 1.009 × 105 M-1, respectively.

A chromone based Schiff base: An efficient colorimetric sensor for specific detection of Cu (II) ion in real water samples

A new chromone based Schiff base ligand L was synthesized by the condensation of 3-formyl chromone and pyrazine-2-carbohydrazide as a colorimetric probe to detect Cu (II) ions selectively. An instant visual colour change from colourless to yellow was obtained on addition of Cu2+ ions to the probe L solution, while other metal ions found ineffective. The ligand L was characterized by 1H NMR, FTIR and HRMS spectral techniques. UV-Visible spectroscopic technique was used to study the sensing ability of probe L for copper ions above other metal ions. The Job's plot obtained from absorption studies and HRMS data confirmed that the Cu2+ ions bind with ligand L in 1:1 stoichiometric ratio. DFT computations were also supported the binding framework between L and Cu (II) ions. The LOD value and the association constant were obtained 3.9 × 10−7 M and 2.3 × 105M−1 respectively, via Benesi-Hildebrand equation. Selectivity of L towards Cu2+ ions was also studied and it was found that the probe L worked specifically for copper ions without any considerable influence of other intruding metal ions. In addition, in real water samples, the ligand L was fully implemented for identification and quantification of Cu2+ ions.

Non-Covalent Bonding Interaction between Primaquine as Guest and 2-(Hydroxypropyl)-β-Cyclodextrin as Host

An inclusion complex of Primaquine (PQ) with 2-(Hydroxypropyl)-β-Cyclodextrin (2-HP-β-CD) in liquid state have been investigated by using absorption and fluorescence spectral techniques. From the spectral data, a binding constant (K) and the stoichiometric ratio between the host-guest system is calculated by using the Benesi–Hildebrand equation. Gibb’s free energy changes of the complexation process are spontaneously at room temperature. The host-guest complex of PQ with 2-HP-β-CD is prepared by various methods like physical mixture, kneading, and co-precipitation methods. The solid inclusion complexes are characterized by using FT-IR, SEM, Powder XRD, and DSC analysis. The orientation and structure of the inclusion complex are proposed based on the results of PM3 optimization. Mutual interactions between the guest (PQ) and host (2-HP-β-CD) are identified by NBO analysis. The anticancer activity also performed for pure PQ and its inclusion complex with 2-HP-β-CD. It clearly showed that the solid complex did not enhances in their anticancer activity than PQ alone.

Investigation of interaction between boronic acids and sugar: effect of structural change of sugars on binding affinity using steady state and time resolved fluorescence spectroscopy and molecular docking

Binding interactions of boronic acid derivatives viz. 2-Methylphenylboronic acid (B1) and 3-Methoxyphenylboronic acid (B2) with mono saccharides (arabinose, fructose and galactose) and disaccharides (sucrose, lactose and maltose) in aqueous condition at pH 7.4 by means of fluorescence spectroscopy is reported in the present investigation. Sugar sensing as well as continuous glucose monitoring (CGM) plays a significant role in diabetes regulation. Sugar sensors mediated through enzymes have their own drawbacks, which led to encouragement to search for designing new sensors through alternate approaches. Among many, fluorescence-based sensors are drawing more attention. Boronic acid-based fluorescence sensors have the capacity to bind reversibly with diols, which makes their demand high in applications. Addition of sugar reduces fluorescence intensities. Change in intensities is associated to cleavage of intermolecular hydrogen bonding which leads in reduced stability of boronate ester. Lineweaver-Burk and Benesi-Hildebrand equation is used for analysing data. Mono sugars are estimated to have higher binding constants. Mutarotation leads to structural changes in saccharides which play a key role in binding interactions. Sugars in furanose form are found to be highly favoured for binding. Molecular docking of B1 and B2 with proteins with PDB ID: 2IPL and 2IPM being periplasmic was done with the help of Schrodinger Maestro 11.2 version. GLIDE scores terms are used for expressing binding affinity.

Enhancement of the biochemical activity of some market antibiotics by chemical modification: Synthesis, characterization, and biochemical evaluation

AbstractThe reaction of isatin with the Ampicillin gave the new compound: (6R)‐3,3‐dimethyl‐7‐oxo‐6‐(2‐(([E]‐2‐oxoindolin‐3‐ylidene)amino)‐2‐phenylacetamido)‐4‐thia‐1‐azabicyclo[3.2.0]hept ‐ane‐2‐carboxylic acid (HAI). The new complexes derived from HAI and Co(II), Ni(II), Cu(II), Eu(III), and Gd(III) were obtained in pure form. The obtained compounds were characterized by elemental analysis, FTIR, UV–Vis, Fluorescence, 1HNMR, Mass spectra, DTA, TGA, Magnetic susceptibility, X‐ray, AAS, and the conductivity of 0.001 M in DMSO. The obtained data indicated the formation of the target complexes: [Co(HAI)(H2O)(NO3)]NO3.4H2O, [Ni(AI)(H2O)2]Cl.2H2O, [Cu(AI)]Cl.H2O, [Eu(AI)(H2O)Cl]Cl.5H2O and [Gd(AI)(H2O)(NO3)]NO3.3H2O. The ligation sites were predicted from the guide of the FTIR and thermal analysis meanwhile the stereochemistry was proved by the UV–Vis and magnetic moment. Co(II) and Ni(II) gave an octahedral structure while Cu(II) gave a square planar form. Molecular modeling, molecular mechanics, and DFT calculations were carried out for the synthesized compounds. The active lone pair and surface properties were obtained and discussed in the silico level. The x‐ray analysis indicates the nanoparticle behavior of the Cu‐AI complex with a monoclinic structure. The interactions of the synthesized complexes with FM‐DNA moiety were investigated through spectrometric titration (UV–vis. spectra) and by using fluorescence spectroscopy. The modes and binding affinities were evaluated and discussed using Benesi–Hildebrand method. Antimicrobial activities of the synthesized compounds have been screened using the disc diffusion method. HAI and Cu‐AI gave activity exceeded the Ampicillin. The docking work was carried using the targeting protein of Escherichia coli FabH (PDB code: 1HNJ). The obtained binding energy was compared and discussed in terms of the in vitro studies.

Physico-chemical study of the interaction between levofloxacin hemihydrate Drug with Cetylpyridinium chloride in aqueous medium: conductometric and spectrophotometric investigation

Herein, the interaction between levofloxacin hemihydrate (LFH), a fluoroquinolone antibiotic drug, and cetylpyridinium chloride (CPC), a cationic surfactant, has been studied by applying conductometric and spectrophotometric techniques at various temperatures. The binding constant of LFH to various types of micelles has also been calculated by means of the Benesi-Hildebrand Equation. (CPC+LFH) mixed system exhibits lower critical micelle concentration (cmc) values in magnitude compared to the pure CPC in aqueous solution at a particular temperature as confirmed by the conductometric measurements. The profound change in the cmc values of the (CPC+LFH) mixtures by varying the concentration of LFH signify the synergistic (attractive) interaction between CPC and LFH. In addition, The negative values of standard free energy demonstrate the stability of the (CPC+LFH) mixture. Furthermore, the other thermodynamic parameters such as the standard enthalpy and standard entropy data suggest the existence of hydrophobic interaction between LFH and surfactants.

Synthesis and spectrophotometric studies of CT complex between 1,2-dimethylimidazole and picric acid in different polar solvents: exploring antimicrobial activities and molecular (DNA) docking

ABSTRACT The charge transfer complex (CT complex) formed in ethanol with 1,2-dimethylimidazole (DMI, donor) and picric acid (PA, π- acceptor) at room temperature (RT) and spectrophotometric studies have been performed in various solvents. CT complex was characterised using different analysis like – 1H NMR, FTIR spectra and UV-vis spectra which designates that CT interaction is connected to proton relocation to DMI from PA followed by the formation of N+–H···O− type bonding. Spectrophotometric data helps in calculating various physical parameters (such as KCT, εCT, ΔGo, ID, RN, ECT, μEN and f) were also obtained through Benesi–Hildebrand equation. From these parameters it was observed that [(DMIH)+(PA)−] formation dependents on type of solvent used. 1:1 stoichiometry of [(DMIH)+(PA)−] was found by a straight-line method. Antimicrobial activity of the CT complex was demonstrated. Molecular docking study give us the information of binding of [(DMIH)+(PA)−] with B-DNA which has substantial application for drug designing.

Spectral study on inclusion interaction and enantiorecognition of 2-aryl carboxylic acids with hydroxypropyl-β-cyclodextrin.

The inclusion interaction between hydroxypropyl-β-cyclodextrin (HP-β-CD) and 21 2-aryl carboxylic acids was investigated by UV (ultraviolet) spectrophotometer. The inclusion constant of each 2-aryl carboxylic acids with HP-β-CD was determined by Benesi-Hildebrand's equation. According to our previous work, it was found that a high inclusion constant for inclusion complex formed by a racemate and cyclodextrin was always observed with the fact that a high enantioseparation factor was achieved for the racemate in enantioseparation by liquid-liquid chromatography, which suggested that high binding combination between racemate and cyclodextrin is very important for a successful enantioseparation in enantioselective liquid-liquid extraction. Among all the studied subjects, mandelic acid enantiomer, 2,3-diphenylpropionic acid enantiomer, and naproxen enantiomer were selected for the further study. The inclusion constants of enantiomers of these three subjects were determined by UV spectra, which indicated that a necessary difference in inclusion constants between enantiomer and cyclodextrin was also essential. It was found in UV spectra that the absorbance of the analytes with the addition of cyclodextrin would increase or decrease, which was determined by the type of electron excitation. The conformation changes of small molecules can lead to the changes of chromophore valence electron clouds distribution, causing the HOMO-LUMO energy difference decreased. Thus, a red shift of the wavelength of the maximum absorption was produced indicating that the possibility of the molecular interaction of enantiomers with HP-β-CD exists.

A novel phenolphthalein-based fluorescent sensor for Al3+ sensing in drinking water and herbal tea samples

In this study, 3,3-bis(4-hydroxy-3-((E)-((4-hydroxyphenyl)imino)methyl) phenyl)isobenzofuran-1(3H)-one (HMBP) was designed as a ‘’turn-on″ fluorogenic chemosensor to detect Al3+. Studies were performed in C2H5OH-HEPES (v/v, 9/1, pH 7.0) media at λem = 475 nm. The LOD value was found to be 0.113 µM. The stoichiometric ratio of HMBP-Al3+ was determined as 1:2 by Job's plot and ESI-MS as well as 1H NMR titration. The binding constant of chemosensor HMBP with Al3+ from the Benesi-Hildebrand equation was determined to be 1.21 × 108 M−1. The quantum (Φ) yields were obtained as 0.040 and 0.775 for the chemosensor HMBP and HMBP-Al3+, respectively. The response of the chemosensor HMBP towards Al3+ was attributed to the strategies of blocking the photo-induced electron transfer (PET) and CN isomerisation mechanisms. Finally, the sensing of the chemosensor HMBP for the determination of Al3+ in real food samples, drinking waters and herbal teas, were employed.

Synthesis, spectroscopic, DNA binding and DFT analysis of new charge transfer complexes of 2-Ethyl-6-methylaniline with DDQ and p-Chloranil

Abstract New charge transfer complexes of 2-Ethyl -6-methylaniline as a donor with π-acceptors 2, 3-dichloro-5, 6-dicyano-p-benzoquinone (DDQ) and 2, 3, 5, 6-tetrachloro-p-benzoquinone (CHL) have been studied spectrophotometrically in acetonitrile solvent at room temperature. The molar composition of the both CT complexes were found to be 1:1 and the stability constant (KCT) and molar extinction coefficient (Ɛ) were estimated by Benesi-Hildebrand equation. Other physical parameters such as energy (ECT), standard free energy (ΔG0), oscillator strength (f), transition dipole moment (μEN), resonance energy (RN), dissociation energy (W) and ionization potential (ID) were also estimated. In addition, the presence of CT complexes was confirmed by IR spectroscopy and the complexes were screened for their pharmacology of DNA binding studies. It was found that the CT complexes could contact with DNA through intercalation and the DFT investigation evaluated the bond lengths, bond angles, Mulliken atomic charges, MEP maps and HOMO-LUMO of CT complexes.

Salen-type Schiff bases spaced by the highly flexible and hydrophobic tetramethyldisiloxane motif. Some synthetic, structural and behavioral particularities

An unusual highly flexible, organic-inorganic diamine, 1,3-bis(3-aminopropyl)tetramethyldisiloxane (APDS), is reacted with 3,5-dichloro-, 3,5-dibromo- and 3-hydroxysalicylaldehyde resulting the salen-type Schiff bases H2L1, H2L2 and H2L3. For comparison, organic homologues derived from 3-hydroxysalicylaldehyde with hexamethylenediamine (H2L4) and dodecamethylenediamine (H2L5) as well as from 2,3-dichlorosalycylaldehyde with hexamethylenediamine (H2L6) and dodecamethylenediamine (H2L7) are prepared. The effects of the presence of siloxane motif in the amine structure on the reaction rate of Schiff base formation and equilibrium conversion, as well as on their behaviour in solution, are studied. Thus, the values of the rate constant determined in the reaction with salicylaldehyde derivatives indicate for these nine atoms spaced-diamine, only slightly lower reactivity than that of the aliphatic diamine (hexamethylenediamine), while the equilibrium conversion is greater than the latter. The high flexibility and hydrophobicity of the tetramethyldisiloxane spacer makes the three resulting compounds to be oily, and show surface activity being able of reducing the surface tension of the DMF and to aggregate in solution, when concentrations exceed the critical micellar concentration. The metal binding capacity of Schiff bases as ligands is assessed by spectrophotometric titration and Benesi-Hildebrand method. The results indicate that the stoichiometry of the complexation remains unchanged during the chemical process, no secondary reactions occur during the considered time range. It has been found that the metal binding constant values for H2L1 vary in order: CuL1 > NiL1 > ZnL1 > CoL1. The binding constant of copper by H2L3 is higher than in the case of organic homologues derived from and hexamethylenediamine and dodecamethylenediamine.

Catalytic activity and DNA binding applications of Benzhydrylpiperazine and p-Chloranil charge transfer complex: Synthesis, spectroscopic, and DFT studies

Abstract The new charge transfer complex (CTC) between Benzhydrylpiperazine (BHP) and p-Chloranil (CHL) has been characterized with experimental and quantum chemical calculations. The electronic spectra is confirmed the formation of the complex through appearing a new absorption band at 553 nm. The composition was studied by Job's and spectrophotometric methods to be 1:2 [BHP:CHL]. The formation constant (KCT) and molar extinction coefficient (e) were assessed by the 1:2 Benesi-Hildebrand equation. The result shows that the investigated complex is stable, exothermic and spontaneous. The complex, [BHP(CHL)2] was found to be significantly active in homogeneous catalysis. Such application gives impetus for investigating these materials as homogeneous catalysts. The planar and extended π-system of CTC was found to be DNA intercalation. The DFT (wB97XD) analysis includes the evaluation of bond lengths, bond angles, Natural atomic charges (through Natural population Analysis), Molecular electrostatic potential maps and delineation of the HOMO–LUMO surfaces of the complex.

Synthesis and spectroscopic characterization of rhodanine azo dyes as selective chemosensors for detection of iron(III)

As the presence of (Fe 3+ ) is strongly associated with many environmental and biomedical analysis, effective sensing methods are of great importance for monitoring Fe 3+ levels in these systems. In this study, we synthesized a new rhodanine-based azo dye ( 4d ) and compared it with compound ( 4c ) which showed the best sensitivity and selectivity among our previously reported compounds. The interaction behaviors with Fe 3+ ions using UV/vis, fluorescence, IR, and NMR spectrometric techniques were investigated. The spectroscopic characterization revealed that azo 4d showed high affinity towards Fe 3+ ions with association constant of 5.35 × 10 8 M −1 . Furthermore, it showed high sensitivity towards Fe 3+ ions with detection limit of 7.05 µM. These results are almost similar to that of azo 4c . The molar ratio and Benesi–Hildebrand methods confirmed the formation of complexes between azo 4c,d and Fe 3+ with 1:2 binding stoichiometry. NMR and IR analyses confirmed the coordination between Fe 3+ and the nitrogen atom of the NH (hydrazone) group and the oxygen atom of the carbonyl (C=O) group. Owing to its good affinity and high sensitivity for Fe 3+ , azo 4d showed excellent potential for developing efficient Fe 3+ chemosensors.