Stability Constants Of Complexes Research Articles

Metal Complexes in Biology and Medicine: The System Cadmium (II)/ Iron (II)/ Zinc (II)- α- Aminobutyric Acid

Metal ions play an important role in biological systems. The importance of metal ions to essential functions of living systems and for wellbeing of living organisms is well known. Complexation reactions of α– aminobutyric acid with cadmium (II), iron (II) and zinc (II) have been studied in solution phase using paper ionophoretic technique. The present method is based upon the migration of a spot of metal ion on a paper strip at different pH values of background electrolyte containing 0.01M α -aminobutyric acid. A graph of pH against mobility was used to obtained information in the binary complexes and to calculate its stability constants. The logarithm stability constants of ML and ML2 complexes of α -aminobutyric acid were found to be (4.01 ± 0.02; 2.72 ± 0.01), (3.73 ± 0.03; 2.65 ± 0.09), (4.45 ± 0.02; 2.80 ± 0.03) for cadmium (II), iron (II) and zinc (II) complexes, respectively at ionic strength 0.1 molL-1 and a temperature of 35º C. Metal based drugs bioactivity can be increase by metal chelation, which in turn increase their absorbance and stability. Metal complexes can offer their action such as anti-inflammatory, anti-diabetic, antimicrobial, anticancer and ant thyroid compounds.

Seasonal studies of aquatic humic substances from Amazon rivers: characterization and interaction with Cu (II), Fe (II), and Al (III) using EEM-PARAFAC and 2D FTIR correlation analyses.

Aquatic humic substances (AHS) are defined asan important components of organic matter, being composed as small molecules in a supramolecular structure and can interact with metallic ions, thereby altering the bioavailability of these species. To better understand this behavior, AHS were extracted and characterized from Negro River, located near Manaus city and Carú River, that is situated in Itacoatiara city, an area experiencing increasing anthropogenic actions; both were characterized as blackwater rivers. The AHS were characterized by 13C nuclear magnetic ressonance and thermochemolysis GC-MS to obtain structural characteristics. Interaction studies with Cu (II), Al (III), and Fe (III) were investigated using fluorescence spectroscopy applied to parallel factor analysis (PARAFAC) and two-dimensional correlation spectroscopy with Fourier transform infrared spectroscopy (2D-COS FTIR). The AHS from dry season had more aromatic fractions not derived from lignin and had higher content of alkyls moities from microbial sources and vegetal tissues of autochthonous origin, while AHS isolated in the rainy season showed more metals in its molecular architecture, lignin units, and polysacharide structures. The study showed that AHS composition from rainy season were able to interact with Al (III), Fe (III), and Cu (II). Two fluorescent components were identified as responsible for interaction: C1 (blue-shifted) and C2 (red-shifted). C1 showed higher complexation capacities but with lower complexation stability constants (KML ranged from 0.3 to 7.9 × 105) than C2 (KML ranged from 3.1 to 10.0 × 105). 2D-COS FTIR showed that the COO- and C-O in phenolic were the most important functional groups for interaction with studied metallic ions.

Preparation, characterization, and in vitro cytogenotoxic evaluation of a novel dimenhydrinate-β-cyclodextrin inclusion complex.

Dimenhydrinate (DMH), used to alleviate motion sickness symptoms such as nausea, vomiting, dizziness, and vertigo, encounters limitations in oral pharmaceutical formulations due to its poor water solubility and bitter taste. Our research hypothesized that inclusion complexation with β-cyclodextrin (β-CD) might address these drawbacks while ensuring that the newly formed complexes exhibit no cytotoxic or genotoxic effects on peripheral blood mononuclear cells (PBMCs). Inclusion complexes were prepared using the kneading method and the solvent evaporation method. The phase solubility analysis, attenuated total reflectance-fourier transform infrared spectroscopy (ATR-FTIR), and differential scanning calorimetry (DSC) were conducted to evaluate the complexation efficacy and stability constant of the new binary systems. The results demonstrated that both methods provided complete and efficient complexation. Cytogenotoxic analysis, including the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) assay, alkaline comet assay, and cytokinesis-block micronucleus cytome (CBMN-cyt) assay, was conducted to assess the cytogenotoxic potential of DMH-β-CD inclusion complexes, a topic previously unexamined. No cytotoxic or genotoxic effects were observed within the concentration range of 36.36 to 109.09 ng/mL. Cell viability of treated PBMCs exceeded 85% for all tested concentrations. No significant increases in DNA strand breaks were observed at any dose, and tail intensity of all complexes remained lower or up to 2.2% higher than the negative control. Parameters indicating genotoxic effects, as well as cytotoxic and cytostatic potential in the CBMN-cyt assay, did not significantly differ from untreated controls. These results suggest that inclusion complexation with β-CD might be a safe and promising solution to overcome the limitations of poor solubility and unpleasant taste of DMH, potentially providing opportunities for new and improved oral pharmaceutical dosage forms.

17-β-Estradiol—β-Cyclodextrin complex as an aqueous solution: Structural and physicochemical characterization supported by MM and QM calculations

17-β-estradiol (EST) is an Active Pharmaceutical Ingredient characterized by a low water solubility. Complexation with β-cyclodextrin (βCD) enhances its bioavailability, hence such complex is an interesting research object from pharmaceutical point of view. However, basic facts like description of complex's structure and definition of its molar ratio, were debatable already for decades. This work for the first time justifies the EST:βCD molar ratio as 1:2 using the HRMS (high-resolution mass spectrometry) and phase solubility studies. The latter are used to define complex stability constant, as well. The structure and stability is analyzed using a variety of computational approaches: Quantum Mechanics (QM) based methods (DFT, semiempirical approaches) and MD/MMGBSA approach. In case of the QM, for the first time in the computational analysis of cyclodextrin complexes, a thorough benchmarking test is presented. Different computational parameters (solvent model, presence/absence of dispersion correction etc.) are used. Obtained results are compared with the experimental data.

Metal Complexes in Biology and Medicine the System Cadmium (II) / Iron (II) /Zinc (II) - Proline

Metal ions are fundamental elements for the maintenance of the life span’ s of the humans, animals and plants. In coordination compound studies, a knowledge of the magnitude of the stability constants of complexes is necessary for preliminary quantitative treatment. Present work described method that involves the use of paper electrophoretic technique for the study of the equilibria in binary complex systems in solution. This method is based on the movement of a spot of metal ion in an electric field at various pHs of the background electrolyte. A plot of overall mobility of metal / complex ion versus pH was used to obtain information on the formation of binary complexes and to calculate their stability constants. The stability constant of the ML and ML2 complexes of cadmium (II) – proline,iron(II) – proline and zinc(II) – proline, have been found to be (4.61 ± 0.01; 3.04 ± 0.03), (4.21 ± 0.01; 2.89 ± 0.09) and (4.98 ± 0.02; 2.44 ± 0.05) (logarithm constant values), respectively at 35 ºC and ionic strength 0.1 mol L-1. The first and second stability constants follow the order zinc (II) >cadmium (II) > iron (II). Metal complexes can offer their action such as anti-inflammatory, antidiabetic, antimicrobial, anticancer and ant thyroid compounds. Metal based drugs bioactivity can be increase by metal chelation, which in turn increase their absorbance and stability.

Heterocyclic fluorescent Schiff base chemosensors for the detection of Fe(III) and Cu(II) ions.

Two new Schiff bases were synthesized from 1-(2,4-dihydroxyphenyl)ethanone and pyridine derivatives. Both compounds were characterized using infrared, UV-Vis., 1H NMR, 13C NMR and mass spectral studies. Density functional theory (DFT) calculations were performed for both the Schiff bases with 6-31G(d, p) as the basis set. Vibrational frequencies calculated using the theoretical method were in good agreement with the experimental values. Both the Schiff bases were highly fluorescent in nature. The cation-recognizing profile of the compounds was investigated in aqueous methanol medium. The Schiff base 4-(1-(pyridin-4-ylimino)ethyl)benzene-1,3-diol (PYEB) was found to interact with Fe(III) and Cu(II) ions, whereas the Schiff base 4,4'-((pyridine-2,3-diylbis(azanylylidene))bis(ethan-1-yl-1-ylidene))bis(benzene-1,3-diol) (PDEB) was found to detect Cu(II) ions. The mechanism of recognition was established as combined excited state intramolecular proton transfer (ESIPT)-chelation-enhanced fluorescence (CHEF) effect and chelation-enhanced quenching (CHEQ) process for the detection of Fe(III) and Cu(II) ions, respectively. The stability constant of the metal complexes formed during the sensing process was determined. The limit of detection for Fe(III) and Cu(II) ions with respect to Schiff base PYEB was found to be 1.64 ×10-6 and 2.16 ×10-7M, respectively. With respect to Schiff base PDEB, the limit of detection for Cu(II) ion was found to be 4.54 ×10-4M. The Cu(II) ion sensing property of the Schiff base PDEB was applied in bioimaging studies for the detection of HeLa cells.

Combination Mechanism of Soil Dissolved Organic Matter and Cu2+ in Vegetable Fields, Forests and Dry Farmland in Lujiang County

Dissolved organic matter (DOM) serves as a critical link in the migration and transformation of heavy metals at the soil–solid interface, influencing the migration behaviour and transformation processes of Cu2+ in soil. There have been studies on the combination mechanisms between DOM and Cu2+ in paddy soils. However, the adsorption/complexation and redox processes between DOM and Cu2+ in other agricultural soil types (such as dry farmland and vegetable fields) are unclear. In order to reveal the combination process of DOM with Cu in different agricultural soil types and the dynamic changes in chemical behaviour that occur, this study analysed the variability of DOM components and structure in three soils using three-dimensional fluorescence spectroscopy and X-ray photoelectron spectroscopy. In addition, the priority order of different DOM compounds in combination with Cu and the change process in relation to the Cu valence state in the soil of Lujiang County, Anhui Province, was revealed based on laboratory experiments. The results showed that the composition of soil DOM was mainly composed of humic-like and fulvic-like substances with a clear terrestrial origin and that the organic matter showed a high degree of decomposition characteristics. The results indicated that the composition of soil DOM is mainly composed of humic and fulvic acid-like substances, and they have obvious characteristics of terrestrial origin. In addition, the soil organic matter showed high decomposition characteristics. The complex stability constants (lgKM) of humic acid-like substances with Cu2+ follow the order of forest land (lgKM = 5.21), vegetable land (lgKM = 4.90), and dry farmland (lgKM = 4.88). The lgKM of fulvic acid-like substances with Cu2+ is in the order of dry farmland (lgKM = 4.51) and vegetable land (lgKM = 4.39). Humic acid-like substances in soil DOM combine preferentially with Cu2+, showing a stronger chelating affinity than fulvic acid-like substances. Cu2+ complexes mainly include hydroxyl, phenolic hydroxyl and amino functional groups are included in soil DOM, accompanied by redox reactions. In comparison to dry farmland, the soil DOM in forest and vegetable fields undergoes more intense redox reactions simultaneously with the chelation of Cu2+. Therefore, the application of organic fertilisers to vegetable and forest soils may lead to uncertainties concerning the fate of heavy metals with variable chemical valence. These results contribute to a deeper understanding of the interaction mechanisms between DOM and Cu2+ in agricultural soils.

Metal Complexes in Biology and Medicine: The System Cadmium ((II))/ Iron ((II))/ Zinc ((II)) - α - Aminobutenoic Acid

Metal ions play an important role in biological system. The importance of metal ions to essential functions of living systems and for wellbeing of living organisms is well known. Metal ions are fundamental elements for the maintenance of life spans of the human, animals, and plants. Recent advances in inorganic chemistry have made possible formation of number of transition metal complexes with organic ligand of interest, which can be used as therapeutic agent. In coordination compounds studies, knowledge of the stability constants of complexes is necessary for preliminary quantitative treatment. The present technique involving the use of paper electrophoresis is described for the study of equilibria in binary complex systems in solution. The method is based on the movement of a spot of a metal ion in an electric field at various pH’s of background electrolyte. A graph of pH versus mobility was used to obtained information in the binary complexes and to calculate its stability constants. Using this method , the stability constants of binary complexes metal (II) – α – aminobutenoic acid have been determined to be ( 3.78 ± 0.01, 2.48 ± 0.03 ); ( 3.27 ± 0.04, 2.33 ± 0.07 ); and (4.45 ± 0.02, 2.66 ± 0.05); (logarithm stability constant values) for cadmium (II), iron (II) and zinc (II) complexes, respectively, at ionic strength 0.01 Mol / L and a temperature of 35º C.

Prediction of stability constants of metal-ligand complexes by machine learning for the design of ligands with optimal metal ion selectivity.

The new LOGKPREDICT program integrates HostDesigner molecular design software with the machine learning (ML) program Chemprop. By supplying HostDesigner with predicted logK values, LOGKPREDICT enhances the computer-aided molecular design process by ranking ligands directly by metal-ligand binding strength. Harnessing reliable experimental data from a historic National Institute of Standards and Technology (NIST) database and data from the International Union of Pure and Applied Chemistry (IUPAC), we train message passing neural net algorithms. The multi-metal NIST-based ML model has a root mean square error (RMSE) of 0.629 ± 0.044 (R2 of 0.960 ± 0.006), while two versions of lanthanide-only IUPAC-based ML models have, respectively, RMSE of 0.764 ± 0.073 (R2 of 0.976 ± 0.005) and 0.757 ± 0.071 (R2 of 0.959 ± 0.007). For relative logK predictions on an out-of-sample set of six ligands, demonstrating metal ion selectivity, the RMSE value reaches a commendably low 0.25. We showcase the use of LOGKPREDICT in identifying ligands with high selectivity for lanthanides in aqueous solutions, a finding supported by recent experimental evidence. We also predict new ligands yet to be verified experimentally. Therefore, our ML models implemented through LOGKPREDICT and interfaced with the ligand design software HostDesigner pave the way for designing new ligands with predetermined selectivity for competing metal ions in an aqueous solution.

Experimental and Theoretical Insight into the Ionic Liquid-Mediated Complexation of Trivalent Lanthanides with β-Diketone and Its Fluorinated Analogue.

A multitechnique approach with theoretical insights has been employed to understand the complexation of trivalent lanthanides with two β-diketones, viz. 1-phenyl-1,3-butanedione (L1) and 4,4,4-trifluoro-1-phenyl-1,3-butanedione (L2), in an ionic liquid (C6mim·NTf2). UV-vis spectral analysis of complexation using Nd3+ revealed the predominance of ML2+ and ML4- species. The stability constants for the PB complexes were higher (β2 ∼ 10.45 ± 0.05, β4 ∼ 15.51 ± 0.05) than those for the TPB (β2 ∼ 7.56 ± 0.05, β4 ∼ 13.19 ± 0.06). The photoluminescence titration using Eu3+ corroborated the same observations with slightly higher stability constants, probably due to the higher ionic potential of Eu3+. The more asymmetric (AL2ML4 ∼ 5.2) Eu-L2 complex was found to contain one water molecule in the primary coordination sphere of Eu3+ with more covalency of the Eu3+-O bond (Ω2L1 = 8.5 × 10-20, Ω4L1 = 1.3 × 10-20) compared to the less asymmetric Eu-L1 complex (AL1ML4 ∼ 3.5) with two water molecules having less Eu-O covalency (Judd-Offelt parameters: Ω2L1 = 7.3 × 10-20, Ω4L1 = 1.0 × 10-20). Liquid-liquid extraction studies involving Nd3+ and Eu3+ revealed the formation of the ML4- complex following an 'anion exchange' mechanism. The shift of the enol peak from 1176 to 1138 cm-1 on the complexation of the β-diketones with Eu3+ was confirmed from the FTIR spectra. 1H NMR titration of the β-diketones with La(NTf2)3 evidenced the participation of α-H of the β-diketones and protons at C2, C4, and C5 positions of the methylimidazolium ring. For the ML2 complex, 4 donor O atoms are suggested to coordinate to the trivalent lanthanides with bond distances of 2.3297-2.411 Å for La-O, 2.206-2.236 Å for Eu-O, and 2.217-2.268 Å for Nd-O, respectively, while for the ML4 complex, 8 donor O atoms were coordinated with bond lengths of 2.506-2.559 Å for La-O, 2.367-2.447 Å for Eu-O, and 2.408-2.476 Å for Nd-O. The Nd3+ ion was higher by 9.7 kcal·mol-1 than that of the La3+ ion for the 1:4 complex. The complexation energy with L1 was quite higher than that with L2 for both 1:2 and 1:4 complexes. Using cyclic voltammetry, the redox behavior of trivalent lanthanides Eu and Gd with β-diketonate in ionic liquid medium was probed and their redox energetic and kinetic parameters were determined.

Enhancing solubility and stability of piperine using β-cyclodextrin derivatives: computational and experimental investigations

Piperine (PP), a natural alkaloid found in black pepper, possesses significant bioactivities. However, its use in pharmaceutical applications is hindered by low water solubility and susceptibility to UV light degradation. To overcome these challenges, we investigated the potential of β-cyclodextrin (βCD) and its derivatives with dimethyl (DMβCD), hydroxy-propyl (HPβCD) and sulfobutyl-ether (SBEβCD) substitutions to enhance the solubility and stability of PP. This study employed computational and experimental approaches to examine the complexation between PP and βCDs. The results revealed the formation of two types of inclusion complexes: the P-form and M-form involving the insertion of piperidine moiety and the methylene-di-oxy-phenyl moiety, respectively. These complexes primarily rely on van der Waals interactions. Among the three derivatives, the PP/SBEβCD complex exhibited the highest stability followed by HPβCD, as attributed to maximum atom contacts and minimal solvent accessibility. Solubility studies confirmed the formation of inclusion complexes in a 1:1 ratio. Notably, the stability constant of the inclusion complex was approximately two-fold higher with SBEβCD and HPβCD compared to βCD. The DSC thermograms provided confirmation of the formation of the inclusion complex between the host and guest. These findings highlight the potential of βCD derivatives to effectively encapsulate PP, improving its solubility and presenting new opportunities for its pharmaceutical applications. Communicated by Ramaswamy H. Sarma

Multipurpose Iron-Chelating Ligands Inspired by Bioavailable Molecules.

Because of their capacity to bind metals, metal chelators are primarily employed for therapeutic purposes, but they can also find applications as colorimetric reagents and cleaning solutions as well as in soil remediation, electroplating, waste treatment, and so on. For instance, iron-chelation therapy, which is used to treat iron-overload disorders, involves removing excess iron from the blood through the use of particular molecules, like deferoxamine, that have the ability to chelate the metal. The creation of bioinspired and biodegradable chelating agents is a crucial objective that draws inspiration from natural products. In this context, starting from bioavailable molecules such as maltol and pyrogallol, new molecules have been synthetized and characterized by potentiometry, infrared spectroscopy and cyclic voltammetry. Finally, the ability of these to bind iron has been investigated, and the stability constants of ferric complexes are measured using spectrophotometry. These compounds offer intriguing scaffolds for an innovative class of versatile, multipurpose chelating agents.

Determination of the Stability Constants of Supramolecular Complexes of Ester Derivatives of Betulin with Randomly Methylated β-Cyclodextrin by Affinity Capillary Electrophoresis

Determination of the Stability Constants of Supramolecular Complexes of Ester Derivatives of Betulin with Randomly Methylated β-Cyclodextrin by Affinity Capillary Electrophoresis

First principle determination of stability constants of metal complexes by cellmetry method

AbstractThe stability constants of 81 metal complexes were calculated using the newly‐developed method which was previously used for determining pK values of acid–base dissociation constants by plane wave functions. Fifteen metal ions and 36 ligands were chosen, and a wide range of the complexes was studied to calculate the logK and logß stability constants. The large variety of geometries and coordination modes allowed us to see the limitation of the method. In some cases, good agreements could be found with the experimental data with an accuracy of .5–1 unit. Results howed that for smaller structural changes, the stability constants can be calculated easily by using the determined parameters. For larger structural differences, rough estimations by 2–4 logK units can be conducted. Correlations could be found among the data which can help further studies as well as aid in the prediction of some unknown complexes. The pK of a hexaaqua metal complex was determined as well.

Adsorption of chalcophile metals onto thiol-based resins: Modeling adsorption capacity and behavior using surface complexation modeling

Adsorption of chalcophile metals from aqueous solution by thiol resins represents an efficient means of reusing these metals and remediating waste streams, and a predictive modeling approach is needed in order to design and optimize adsorption applications. In this study, potentiometric titration measurements, metal adsorption experiments and surface complexation modeling (SCM) approaches were used to characterize three thiol-based resins (BT40, SP70, and SP300), and to model their proton, Cd, Zn, and Pb adsorption capacities and behaviors. We find that the extent of Cd adsorption onto the three resins correlates strongly to the measured concentration of proton-active thiol sites on each resin, and that the BT40 resin has a significantly higher concentration of proton-active thiol sites than the other two resins tested. Using the BT40 as a model resin, we demonstrate that the measured stability constant (K) of the Cd-thiol surface complex on the resin successfully accounts for the effects of both the metal:resin ratio and pH over a wide range of experimental conditions. We also find that a linear free-energy relationship (LFER) exists between the K values of metal-thiol surface complexes on the BT40 resin and the K values of metal-thiol aqueous complexes for Cd, Zn and Pb. This LFER can be used to estimate the K values of other metal-thiol resin surface complexes that have not been measured experimentally, therefore enabling prediction of the adsorption behavior of a wide range of metals onto thiol-based resins under a wide range of system conditions. This study demonstrates that a SCM approach, coupled with potentiometric titration measurements and metal adsorption experiments, represents a powerful tool for the design and optimization of strategies for separating and recovering chalcophile metals from aqueous media.

Implicatons of Metal Complexes in Biology and Medicine the System Cadmium (II)/ Iron (II)/ Zinc (II)-Hydroxyproline

The importance of metal ions to essential functions of living systems and for the well being of living organisms is known. Metal ions are fundamental elements for the maintenance of the life spans of the human, animals and plants. The stability constants of Cd2+, Fe2+ and Zn2+ complexes with hydroxyproline were determined by Paper Electrophoretic Technique (PET). This method is based on the movement of a spot of metal ion in an electric field at various pH of background electrolyte. A graph of pH against mobility gives information about the formation of binary complexes and permit to calculate their stability constants. The stability constant of the ML and ML2 complexes of Cd (II) – hydroxyproline, Fe (II) – hydroxyproline and Zn (II) – hydroxyproline, have been found to be (4.41 ± 0.01; 2.95 ± 0.06) (4.11 ± 0.01; 2.81 ± 0.11 and (4.83 ± 0.02; 3.28 ± 0.07) ( logarithm stability constant values), respectively at ionic strength 0.1 mole L-1 (per chloric acid as background electrolyte) and a temperature of 35 0C, The first and second stability constants of metal complexes follow the order Zn (II) > Cd (II) > Fe (II). Metal complexes can offer their action such as anti-inflammatory, antibiotic, anti-thyroid and anticancer compounds. Metal based drugs bioactivity can be increased by metal chelation, which in turn increase their absorbance and stability. Recent advances in inorganic chemistry have made possible formation of a number of metal complexes with organic ligands of interest which can be use as therapeutic agents.

Design, virtual screening and in silico QSPR modeling for the development of new thiosemicarbazone‐based complexes

AbstractEighteen new thiosemicarbazone ligands and 30 new ligand‐based complexes were developed from quantitative structure‐property relationships (QSPR) methods. Stability constants (logβ12) of complexes were calculated on QSPR models that were built by methods of multivariate linear regression (MLR) and artificial neural network (ANN). Six descriptors, including dipole, 5C, 4N, fw, xc3, and ka1 were discovered in the best QSPRMLR model with the good statistical criteria: R2train = 0.892, Q2CV = 0.845, and SE = 0.900. Besides, the ANN model with architecture I(6)‐HL(3)‐O(1) was built from the descriptors of the MLR model with excellent results as R2train = 0.958, Q2CV = 0.966, and Q2test = 0.980. Also, the models were externally validated on the other experimental dataset. Consequently, the resulting QSPR models could be applied to develop new complexes for chemically related fields.

Impedance data as a possible basis for finding stability constants of cucurbituril complexes with inorganic cations

An analysis of the array of impedance data for the interface the Hg-electrode/salt solutions of macrocyclic cavitands of the cucurbituril family containing their supramolecular cationic complexes was performed. A significant change in the properties of the adsorption layer was established with a change in the charge of the electrode surface and the concentrations of the components of the complex formation reaction. The existence of two types of adsorption layer was found, one of which (with positive charges on the electrode surface) is formed with the participation of neutral cavitand molecules. The high sensitivity of the impedance data to the presence of these molecules in solution made it possible to establish the corresponding quantitative dependences for systems with known values of the stability constants of cationic complexes. It is shown that these data can be used to find previously unknown stability constants of cationic complexes of a given cavitand formed in other similar salt systems. The applicability of the proposed method was demonstrated using impedance data for systems with known stability constants of cationic complexes (cucurbit[6]uril + Me2 SO4, Me+ = K+, Na+).

PH-metric titration technique for the study of metal-complexes of substituted 2- Oxo-2H-Chromene-3-Carbohydrazide derivatives in solution: calculation of stability constants

Background: In coordination chemistry, the stability of complexes is expressed in terms of the formation constant of complexes. In coordination complexes, the temperature is very important. It plays an important role in complex formation reaction. Temperature affects metal-ligand stability constant (log K) and proton-ligand stability constant (pK). The metal ion Mn2+, Co2+, Ni2+, and Cu2+ at different temperatures form complexes with 4-sulfamethoxazoleazo-3-methyl-2-pyrazolin-5-one are reported. The metal-ligand stability constant (logK) and proton-ligand stability constant (pK) of Mn(II), Co(II), Ni(II), Cu(II), and Zn(II) with organic ligand n-[2-hydroxy-1-napthalydene]-2-methylanilline at 0.1 M ionic strength in 60% dioxane-water medium is studied. The study of thermodynamic parameters and stability constant of complexes of substituted thiazole Schiff bases with rare earth metal ions in mixed solvent is reported. Objective: The study of coordination compounds and a lot of work has been done on metal-ligand stability constant. The same transition metal ion form complexes with substituted pyrazole for this metal-ligand stability constant are determined. Method: Pointwise Calculation Method Half Integral Method. Result: The values of logK1 and logK2 are determined from the metal-ligand formation curve at formation numbers 0.5 and 1.5. In all cases, logK1 is greater than logK2. The ratio logK1/logK2 is positive and greater than one in all systems. This implies that there is little or no steric hindrance to the addition of the secondary ligand molecules. The difference between logK1 - logK2 is usually positive. If the difference between logK1 and logK2 is less than 2.5, simultaneous formation of 1:1 and 1:2 complexes occurs and if it is more than 2.5, then stepwise complex formation occurs. In the present case, in all systems, it is less than 2.5. This indicates the simultaneous formation of 1:1 and 1:2 complexes takes place. Conclusion: A pH-metric study of Substituted 2-oxo-2H-chromene-3-carbohydrazide derivatives with metal ions Fe(III), and Mn(II) occurs. The graphical representation of the curve shows that the acid + ligand curve is separated from the corresponding acid + ligand + metal curve in this system. The formation of a complex is indicated. Half integral method and pointwise calculation method give nearly similar results. The values of stability constants for all systems indicate that the complexes formed in these processes are stable.

Synthesis of Cationic Biphen[4, 5]arenes as Biofilm Disruptors

AbstractSince bacteria in biofilms are inherently resistant to antibiotics and biofilm‐associated infections pose a serious threat to global public health, new therapeutic agents and schemes are urgently needed to meet clinical requirements. Here two quaternary ammonium‐functionalized biphen[n]arenes (WBPn, n=4, 5) were designed and synthesized with excellent anti‐biofilm potency. Not only could they inhibit the assembly of biofilms, but also eradicate intractable mature biofilms formed by Gram‐positive S. aureus and Gram‐negative E. coli bacterial strains. Moreover, they could strongly complex a conventional antibiotic, cefazolin sodium (CFZ) with complex stability constants of (7.41±0.29)×104 M−1 for CFZ/WBP4 and (4.98±0.49)×103 M−1 for CFZ/WBP5. Combination of CFZ by WBP4 and WBP5 synergistically enhanced biofilm eradication performance in vitro and statistically improved healing efficacy on E. coli‐infected mice models, providing a novel supramolecular strategy for combating biofilm‐associated infections.