Potentiometry, Stability and Thermodynamics of Diethyltin(IV) Dichloride with Some Selected Biomolecules

The interaction of diethyltin(IV), DET, with selected bioligands having a variety of model functional groups was investigated at 25 °C and ionic strength 0.1 mol·dm^?3 NaCl using the potentiometric technique. The hydrolysis constants of the DET cation and the formation constants of the complexes formed in solution were calculated using the MINIQUAD-75 program. The stoichiometry and stability constants for the complexes formed are reported. The results show the formation of 1:1 and 1:2 complexes with amino acids and DNA constituents. The dicarboxylic acids form 1:1 complexes. The peptides form both 110 complexes and the corresponding deprotonated amide species [Et₂Sn(LH_?1)] (11-1). The participation of different ligand functional groups in binding to organotin is discussed. The concentration distributions of the various complex species were evaluated as a function of pH. The standard thermodynamic parameters ΔH° and ΔS°, calculated from the temperature dependence of the equilibrium constants, were investigated for the interaction of DET with thymine as a representative example of DNA constituents. The effect of ionic strength and solvent on hydrolysis constants of DET, protonation equilibria of thymine and its complex formation with DET were investigated and discussed.     

Complex Formation Equilibria of Unusual Seven Coordinate Fe(III) Complexes with DNA Constituents

Seven-coordinate Fe(III) complexes [Fe(dapsox)(H₂O)₂]⁺, where [dapsox = 2,6-diacetylpyridine-bis(semioxamazide)] is an equatorial pentadentate ligand with five donor atoms (2O and 3N), were studied with regard to their acid–base properties and complex formation equilibria. Stability constants of the complexes and the pK _a values of the ligands were measured by potentiometric titration. The interaction of [Fe(dapsox)(H₂O)₂]⁺ with the DNA constituents, imidazole and methylamine·HCl were investigated at 25 °C and ionic strength 0.1 mol·dm^?3 NaNO₃. The hydrolysis constants of the [Fe(dapsox)(H₂O)₂]⁺ cation (pK _a1 = 5.94 and pK _a2 = 9.04), the induced ionization of the amide bond and the formation constants of the complexes formed in solution were calculated using the nonlinear least-squares program MINIQUAD-75. The stoichiometry and stability constants for the complexes formed are reported. The results show the formation of 1:1 and 1:2 complexes with DNA constituents supporting the hepta-coordination mode of Fe(III). The concentration distributions of the various complex species were evaluated as a function of pH. The thermodynamic parameters ΔH° and ΔS° calculated from the temperature dependence of the equilibrium constants were investigated for interaction of [Fe(dapsox)(H₂O)₂] with uridine.     

New cyclen derivative ligand for thorium(IV) separation by solvent extraction

A new N-containing ligand, 1,4,7,10-tetra-(4-nitrobenzyl)-1,4,7,10-tetraazacyclo-dodecane (L), was synthesized, and its structure was determined by ¹H NMR, high resolution mass spectrometry and X-ray diffraction. L crystallized in the monoclinic system (P2₁/n space group; a = 7.7895(2) Å, b = 22.9592(5) Å, c = 9.9204(2) Å; α = 90.00°, β = 105.481(3)°, γ = 90.00°; Z = 2). Slope analysis and the continuous variation method demonstrated that 1:2 complexes between Th(IV) and L are formed; furthermore, the XPS analysis suggested that two oxygen atoms might be provided by two water molecules and that eight nitrogen atoms might be provided by two L molecules to form a ten-coordinate compound with Th(IV). The extraction equilibrium constant for the complex formation between Th(IV) and L was logK _ex = 6.95 ± 0.15 (25 °C), and the Gibbs free energy, ΔG ^o (25 °C), of the 1:2 Th–L complex in dichloromethane was ?39.56 kJ/mol. The L ligand in dichloromethane only slightly extracted Th(IV) from HNO₃ solution at pH = 1–3; however, an extraction efficiency of E = 94.9 ± 0.3 % was observed at pH = 4.63. The selectivity of L for the Th(IV) cation over other cations (i.e., Cs(I), Sr(II), Y(III), La(III), Sm(III), Eu(III), U(VI), and ²⁴¹Am(III)) was evaluated. Furthermore, the stripping experiments showed that the stripping agent (0.5 mol/L Na₂CO₃ + 0.1 mol/L EDTA) could provide an optimal condition for stripping thorium, and thorium recovery was up to 91.6 ± 0.1 %.     

Coordination properties of bidentate (N,O) and tridentate (N,O,O) heterocyclic alcohols with dimethyltin(IV)

The complex-formation equilibria of dimethyltin(IV) (DMT) with 4-hydroxymethyl imidazole (HMI) and 2,6-dihydroxymethyl pyridine (PDC) have been investigated. Stoichiometry and stability constants for the complexes formed were determined at different temperatures and 0.1?mol?L^?1 NaNO₃ ionic strength. The concentration distribution of the complexes in solution was evaluated as a function of pH. The effect of dioxane as a solvent on both protonation constants and formation constants of DMT complexes with HMI and PDC are discussed. The thermodynamic parameters ΔH° and ΔS° calculated from the temperature dependence of the equilibrium constants were investigated.     

Equilibrium Studies of Dibutyltin(IV)–Zwitterionic Buffer Complexation

Equilibrium studies in aqueous solution are reported for dibutyltin(IV) (DBT) complexes of the zwitterionic buffers “Good’s buffers” Mes and Mops. Stoichiometric and formation constants of the complexes formed were determined at different temperatures and ionic strength 0.1 mol·L^?1 NaNO₃. The results show that the best fit of the titration curves were obtained when the complexes ML, MLH_?1, MLH_?2 and MLH_?3 were considered beside the hydrolysis product of the dibutyltin(IV) cation. The thermodynamic parameters ΔH ^o, ΔS ^o and ΔG ^o calculated from the temperature dependence of the formation constant of the dibutyltin(IV) complexes with 2-(N-morpholino)ethanesulfonic acid (Mes) and 3-(N-mor-pholino)-propanesulfonic acid (Mops) were investigated. The effect of dioxane as a solvent on the formation constants of DBT–Mes and DBT–Mops complexes decrease linearly with the increase of dioxane proportion in the medium. The concentration distribution of the various complexes species was evaluated as a function of pH.     

Calorimetric investigation of the complex formation reaction of 18-crown-6 ether with d,l-alanine in water–ethanol mixtures

The standard thermodynamic parameters (Δ_r G°, Δ_r H°, and TΔ_r S°) of the reaction of molecular complex formation of 18-crown-6 ether (18C6) with d,l-alanine (Ala), [Ala18C6], have been obtained from calorimetric titration experiments carried out using the microcalorimetric system TAM III (TA Instruments, USA) at T = 298.15 K in water–ethanol (H₂O–EtOH) solvents at X _EtOH = 0 ÷ 0.6 mol fractions. Results show that the increase of the EtOH concentration in solvent brings about an increase of the [Ala18C6] complex stability and of the exothermicity of the reaction of complex formation. The solvation contributions of 18C6, Ala, [Ala18C6] to Δ_r G° and Δ_r H° at various X _EtOH values are also analyzed.     

Removal of Th(IV), Ni(II)and Fe(II) from aqueous solutions by a novel PAN–TiO<Subscript>2</Subscript> nanofiber adsorbent modified with aminopropyltriethoxysilane

A novel polyacrylonitrile (PAN)–titanium oxide (TiO₂) nanofiber adsorbent functionalized with aminopropyltriethoxysilane (APTES) was fabricated by electrospinning. The adsorbent was characterized by SEM, FTIR, TEG and BET analyses. The pore diameter and surface area of the adsorbent were 3.1 nm and 10.8 m² g^?1, respectively. The effects of several variables, such as TiO₂ and amine contents, pH, interaction time, initial concentration of metal ions, ionic strength and temperature, were studied in batch experiments. The kinetic data were analyzed by pseudo-first-order, pseudo-second-order and double-exponential models. Two isotherm models, namely Freundlich and Langmuir, were used for analysis of equilibrium data. The maximum adsorption capacities of Th(IV), Ni(II) and Fe(II) by Langmuir isotherm were found to be 250, 147 and 80 mg g^?1 at 45 °C with pH of 5, 6 and 5, respectively, and greater adsorption of Th(IV) could be justified with the concept of covalent index and free energy of hydration. Calculation of ΔG°, ΔH° and ΔS° demonstrated that the nature of the Th(IV), Ni(II) and Fe(II) metal ions adsorption onto the PAN–TiO₂–APTES nanofiber was endothermic and favorable at a higher temperature. The negative values of ΔG° for Th(IV) showed that the adsorption process was spontaneous, but these values for Ni(II)and Fe(II) were positive and so the adsorption process was unspontaneous. Increasing of ionic strength improved the adsorption of Ni(II) and Fe(II) on nanofiber adsorbent but decreased the adsorption capacity of Th(IV). The adsorption capacity was reduced slightly after six cycles of adsorption–desorption, so the nanofiber adsorbent could be used on an industrial scale. The inhibitory effect of Ni(II) and Fe(II) on the adsorption of Th(IV) was increased with an increase in the concentration of inhibitor metal ions.     

Extending the hydrophobic cavity of β-cyclodextrin results in more negative heat capacity changes but reduced binding affinities

The formation of inclusion complexes of hydroxypropylated β-cyclodextrins (CDs) with three bile salts are investigated to shed light on the role played by the hydroxypropyl (HP) substituents. The HP-chains are situated at the rim of the CD and may thus extend the hydrophobic cavity of the CD. Calorimetric titrations in a broad temperature range and molecular dynamics simulations confirm previous speculations that the HP-chains cause an increase in dehydrated nonpolar surface area upon formation of the complexes. This additional burial of nonpolar surface area, 12–16 Å² per HP-chain according to the MD simulations, results in more negative values of ΔC _p °, which are in quantitative agreement with what is expected for hydrophobic dehydration. Although these observations support the picture of an extended hydrophobic cavity, HPβCD complexes were less stable than their unsubstituted counterparts. This indicates that increased hydrophobic contacts are not always accompanied by increased binding strength. The linear dependence of ΔC _p °, ΔH° and ΔS° on the number of HP-chains give rise to isoentropic and isoenthalpic temperatures at which ΔH° and ΔS° are independent of the number of HP-chains on the host CD (but depend on the type of bile salt). Interestingly, these convergence temperatures are close to what is observed for unfolding of proteins and may be a common feature of hydrophobic dehydration.     

Thermodynamic studies of inclusion complex formation between alkylpyridinium chlorides and β-cyclodextrin using conductometric method

Thermodynamics on inclusion complexation of β-cyclodextrin (β-CD) with n-alkylpyridinium chlorides (C _n PC, n = 12, 14, 16) were measured by conductivity technique to evaluate the effects of chain length of C _n PC and temperature. The data obtained indicate that inclusion complexes S(CD) and S(CD)₂ had formed between surfactant and β-CD in aqueous solution. Investigation showed that the K ₁ (first equilibrium constant) for S(CD) formation is greater than K ₂ (second equilibrium constant) for S(CD)₂ formation. It has been found that C₁₂PC forms only the 1:1 complex, while C₁₄PC and C₁₆PC form 1:1 and 1:2 complexes. Thermodynamic parameters of the complexation, i.e. ΔG°, ΔH° and ΔS° have been also calculated. The large values of ΔG° indicate that complexation between surfactant and β-CD is very favorable.     

Synthesis,spectroscopic and thermodynamic studies of new transition metal complexes with N,N′-bis(2-hydroxynaphthalin-1-carbaldehydene)-1,2-bis(m-aminophenoxy)ethane and their determination by spectrophotometric methods

A novel tetradentate N₂O₂-type Schiff base, synthesized from 1,2-bis(m-aminophenoxy)ethane and 2-hydroxynaphthalin-1-carbaldehyde, forms stable complexes with transition metal ions such as Cu(II), VO(IV) and Zn(II) in DMF. Microanalytical data, elemental analysis, magnetic measurements, UV, visible and IR spectra as well as conductance measurements were used to confirm the structures. The stability constants of these complexes in 60% (v/v) DMF–water were determined at different ionic strengths (0.07,?0.13,?0.2?M) and at different temperatures (45,?50,?55,?60?±?0.1°C) using a spectrophotometric method. From these constants, thermodynamic stability constants and thermodynamic parameters (ΔG?⁰, ΔH?⁰, ΔS?⁰) were calculated. The values of enthalpy change are negative for all systems. The acid dissociation constant of the ligand, investigated in 60% (v/v) DMF–water, has also been calculated at different temperatures.     

Octadecylamine cobalt(III) dimethyl glyoximato complexes: synthesis,thermodynamics of micellization,steady-state photolysis and biological activities

A new class of surfactant–cobalt(III) complexes of the type trans-[Co(DH)₂(OA)X], where DH = dimethylglyoxime, OA = octadecylamine, X = Cl^?, Br^?, I^?, N₃ ^?, NO₂ ^?, SCN^? or OA, were synthesized and characterized by physicochemical and spectroscopic methods. The critical micelle concentration (CMC) values of these surfactant–cobalt(III) complexes in ethanol solution were obtained by measuring absorption at ~250 nm. Specific conductivity data (at 303–313 K) served for the evaluation of the temperature-dependent CMC and the thermodynamics of micellization (ΔG _m ⁰ , ΔH _m ⁰ and ΔS _m ⁰ ). Steady-state photolysis and cyclic voltammetry of the complexes were studied. The surfactant–cobalt(III) complexes were screened for their antibacterial and antifungal activities against various microorganisms.     

A thermodynamic study of interaction of Ag+, Mg2+, Ca2+, and K+ cations with 4-hydroxyphenyl-2,5-bis(2-benzofuranyl)pyridine in some binary mixed non-aqueous solvents

In the present work the complexation process between Ag⁺ and Mg²⁺ cations and 4-hydroxyphenyl-2,5-bis(2-benzofuranyl)pyridine (HBFPY) ligand was studied in pure dimethylformamide (DMF), ethanol (EtOH), acetonitrile (AN) and in (DMF-EtOH), (AN-EtOH) and (DMF-AN) binary mixed solvent solutions at different temperatures using the conductometric method. Also in this work the complexation reaction between Ca²⁺, K⁺ cations and HBFPY ligand, was studied in pure dimethylformamide (DMF), propanol (PrOH), 1,4-dioxane (DOX), ethanol (EtOH) and in DMF-PrOH, DMF-DOX and DMF-EtOH binary mixed solvent solutions at different temperatures using the conductometric method. The conductance data show that the stoichiometry of the complexes formed between this ligand and the studied cations is 1 : 1 [ML]. In most cases, addition of HBFPY to solutions of these cations, causes a continuous increase in the molar conductivities which indicates that the mobility of complexed cations is more than the uncomplexed ones. The stability constants of the complexes were obtained from fitting of molar conductivity curves using a computer program, GENPLOT. The stability constant of [Mg(HBFPY)]²⁺ complex in various neat solvents at 15°C decreases in order: EtOH > DMF > AN and the stability constant of [Ag(HBFPY)]⁺ complex in various neat solvents at 35°C decreases in order: DMF > EtOH. The values of standard enthalpy changes (ΔH° _c ) for complexation reactions were obtained from the slope of the Van’t Hoff plots and the changes in standard entropy (ΔS° _c ) were calculated from the relationship ΔH° _c,295.15= ΔH° _c –298.15ΔS° _c .     

Computational and experimental study on the interaction of three novel rare earth complexes containing 2,9-dimethyl-1,10-phenanthroline with human serum albumin

In this paper, several rare earth [terbium(III), ytterbium(III) and yttrium(III)] complexes containing 2,9-dimethyl-1,10-phenanthroline (Me₂Phen) were successfully synthesized and characterized by means of elemental analysis (CHN), infrared spectroscopy (FT-IR), UV–vis absorption spectroscopy and ¹HNMR. To explore the potential medicinal value of these complexes (MMe₂Phen), their binding interactions with human serum albumin (HSA) were investigated through UV–vis and fluorescence spectroscopies and also molecular docking examinations. The thermodynamic parameters, binding forces and Förster resonance distance between these complexes and Trp-214 of HSA were estimated from the analysis of fluorescence measurements. The values of estimated binding constants (K_b) ranging for the formation of MMe₂Phen:HSA complex were in the order of 10⁵ M^?1. The thermodynamic parameters determined by van’t Hoff analysis of K_b (ΔH°?<?0 and ΔS°?<?0) clearly indicate the major rules of hydrogen bonds and van der Waals interactions in the formation process of MMe₂Phen:HSA. The values of Stern–Volmer constant and the evaluation of dynamic quenching constant at various temperatures provided good evidences for static quenching mechanism. Furthermore, the results of molecular docking calculation and competitive binding experiments represent the binding of these complexes to site 3 of HSA located in subdomain IB, containing both polar and apolar residues. The consistency of computational and experimental results, according to the binding sites and the order of binding affinities (TbMe₂Phen?>?YbMe₂Phen?>?YMe₂Phen), supports the accuracy of docking calculation.     

Calorimetric analysis of the multiple melting behavior of melt-crystallized poly(l-lactic acid) with a low optical purity

The polymorphous crystallization and multiple melting behavior of poly(l-lactic acid) (PLLA) with an optical purity of 92 % were investigated after isothermally crystallized from the melt state by wide-angle X-ray diffraction and differential scanning calorimetry. Owing to the low optical purity, it was found that the disordered (α′) and ordered (α) crystalline phases of PLLA were formed in the samples crystallized at lower (<95 °C) and higher (≥95 °C) temperatures, respectively. The melting behavior of PLLA is different in three regions of crystallization temperature (T _c) divided into Region I (T _c < 95 °C), Region II (95 °C ≤ T _c < 120 °C), and Region III (T _c ≥ 120 °C). In Region I, an exothermic peak was observed between the low-temperature and high-temperature endothermic peaks, which results from the solid–solid phase transition of α′-form crystal to α one. In Region II, the double-melting peaks can be mainly ascribed to the melting–recrystallization–remelting of less stable α crystals. In Region III, the single endotherm shows that the α crystals formed at higher temperatures are stable enough and melt directly without the recrystallization process during heating.     

Stability Constants and Spectroscopic Properties of Thorium(IV)–Arsenazo III Complexes in Aqueous Hydrochloric Medium

The complexation characteristics of thorium–arsenazo III in the range of 1–6 mol·L^?1 hydrochloric acid media were investigated by UV–Vis absorption spectroscopy and computational analysis. The chemical equilibrium model of thorium–arsenazo III complexation was established including the species distribution of arsenazo III, the formation of thorium chloride species, and the release of protons from thorium–arsenazo III complexes. In the spectra of thorium–arsenazo III complexes, two characteristic absorption peaks were observed at 610 and 660 nm, and the latter peak showed a tendency to shift about 4 nm to higher wavelength as the acidity of the hydrochloric acid media increased from 1 to 6 mol·L^?1. Analysis of the experimental data indicates that the molar absorptivities of both 1:1 and 1:2 complexes (thorium to arsenazo III) steadily increase as the acidity of medium increases. The determined stability constants of 1:1 and 1:2 complexes at various concentrations of hydrochloric acid were extrapolated to zero ionic strength, based on the specific ion interaction theory (SIT) approach. The limiting stability constants were determined to be \( { \log }_{10} \beta_{11}^{\text{o}} \) = 8.56 ± 0.13 and \( {\log}_{10} \beta_{12}^{\text{o}} \) = 15.17 ± 0.18 with ion interaction coefficients of Δε ₁₁ = –0.57 ± 0.02 kg·mol^?1 and Δε ₁₂ = –0.60 ± 0.04 kg·mol^?1, respectively.     

Diethylenetriamine-functionalized chitosan magnetic nano-based particles for the sorption of rare earth metal ions [Nd(III), Dy(III) and Yb(III)]

The recovery of three rare earth (RE) metals ions [Yb(III), Dy(III) and Nd(III), belonging to heavy, mild and light REs, respectively] was investigated using hybrid chitosan-magnetic nano-based particles functionalized by diethylenetriamine (DETA). The effect of pH on sorption performance was analyzed: the optimum initial pH value was found close to 5 (equilibrium pH value close to 6.5). The nanometric size of sorbent particles (30–50 nm) minimized the contribution of resistance to intraparticle diffusion on the control of uptake kinetics, which is efficiently modeled using the pseudo-second order rate equation: under selected experimental conditions the contact time required for reaching equilibrium was less than 1 h. Sorption isotherms were efficiently modeled using the Langmuir equation: maximum sorption capacities reached about 50 mg metal g^?1, regardless of the RE. The temperature had a very limited effect on sorption capacity (in the range 300–320 K). The thermodynamic parameters were determined: the sorption was endothermic (positive values of ΔH°), spontaneous (negative values of ΔG°) and contributed to increasing the disorder of the system (positive values of ΔS°). The three REs have similar sorption properties on DETA-functionalized chitosan magnetic nano-based particles: the selective separation of these elements seems to be difficult. The sorbed metal ions can be removed from loaded sorbents using thiourea, and the sorbent can be recycled for at least five sorption/desorption cycles with a limited loss in sorption performance (by less than 6 %). The saturation magnetization was close to 20 emu g^?1; this means that nano-based superparamagnetic particles can be readily recovered by an external magnetic field, making the processing of these materials easy.     

Solvent influence upon complex formation between benzo-15-crown-5 and Mg2+, Ca2+ and Sr2+ cations in some pure and binary mixed solvents using conductometric method

The complexation reactions between Mg²⁺, Ca²⁺ and Sr²⁺ cations with the macrocyclic ligand, benzo-15-crown-5 (B15C5), in pure acetonitrile, water, methanol and tetrahydrofuran and also in acetonitrile–water (AN–H₂O) and in methanol–tetrahydrofuran (MeOH–THF) binary mixtures have been studied at different temperatures using conductometric method. The conductance data show that the stoichiometry of the complexes in most cases is 1:1 [ML]. But in the case of Ca²⁺ cation a 1:2 [ML₂] complex is formed in pure THF, which shows that the stoichiometry of the complexes may be changed by the nature of the medium. The values of stability constants of complexes, which were obtained from conductometric data, show that the stability of complexes is affected by the nature and composition of the binary mixed solvents and a non-linear behavior was observed for variation of logK_f of the complexes versus the composition of the solvent systems. The results show that the selectivity order of B15C5 for the metal cations in two AN–H₂O binary solutions (mol% AN = 25.71 and 50.94) at 25 °C is: Mg²⁺ > Sr²⁺ > Ca²⁺. The values of thermodynamic parameters (ΔH _c ⁰ , ΔS _c ⁰ ) for formation of complexes were obtained from temperature dependence of stability constants of complexes using the van’t Hoff plots. The results show that the values and also the sign of these parameters are influenced by the nature and also the composition of the binary mixed solvents.     

Equilibrium anionic polymerization of the isopropenyl monomers containing aromatic heterocycles

The anionic polymerization of three monomers, 2-isopropenyl-4,5-dimethyloxazole(I), 2-isopropenylthiazole(II), and 2-isopropenylpyridine(III), was studied in THF. These monomers produced red-colored living polymers on addition of sodium naphthalene or living α-methylstyrene tetramer as an initiator. It was observed that a considerable amount of monomer remained in the respective living polymer–monomer system, indicating that an equilibrium between the polymer and the monomer existed as in the case of α-methylstyrene. At lower temperatures, the conversion of the monomer to the polymer increased. The equilibrium monomer concentrations [M_e] were determined at different temperatures, and the heats (ΔH) and the entropies (ΔS°) of polymerization were obtained by plotting In(1/[M_e]) against 1/T as ΔH = ?9.4, ?6.8, and ?6.2 kcal/mole, ΔS°S = ?22.9, ?16.5, and ?16.6, eu for I, II, and III, respectively.     

Preparation of high-purity thorium by solvent extraction with di-(2-ethylhexyl) 2-ethylhexyl phosphonate

The extraction behavior of thorium(IV) by di-(2-ethylhexyl) 2-ethylhexyl phosphonate (DEHEHP, B) from nitric acid media has been investigated. The influence factors including the concentration of HNO₃, salting-out reagents, temperature, the concentration of metal ions and DEHEHP have been examined systematically. A possible extraction mechanism is proposed and the extracted species as Th(NO₃)₄·2B _(o) is confirmed by the slope analysis method. The extraction equilibrium constants (K _ex) and thermodynamic parameters (ΔG, ΔH and ΔS) were calculated under the present experimental conditions. DEHEHP shows a high selectivity of thorium(IV) over rare earths(III). Stripping study indicates that thorium can be completely stripped by distilled water from the Th-loaded DEHEHP. Furthermore, a solvent extraction process including six extraction stages, six scrubbing stages, and six stripping stages was designed for the preparation of highly pure thorium from thorium concentrate with DEHEHP as extractant in laboratory scale, and finally thorium product can be obtained with a purity of 99.999 % and a yield of 98 %.     

Synthesis and properties of transition and lanthanide complexes with benzyl monohydrazone-3-hydrazine- 4-benzyl-6-phenyl pyridazine ligand (BHP)

Synthesis and characterization of benzyl-monohydrazone-3-hydrazino-4-benzyl-6-phenyl pyridazine (BHP) and its complexes with copper(II), nickel(II), cobalt(II), zinc(II), manganese(II), cadmium(II), thorium(IV), dioxyuranium(VI), samarium(III) and erbium(III) are presented. The protonation equilibrium of BHP ion and complex formation equilibrium with the metal ions have been studied by potentiometry in 75% (v/v) dioxane-water and 0.10M KNO₃ at different temperatures (10, 20, 30 and 40°C). A series of mononuclear complexes [ML _n ]^{(1? z )+} (L^? =?BHP and n =?1 ??z) were found in solution and their formation constants, enthalpies and entropies were determined.

The solid metal complexes and corresponding thermal products were elucidated by elemental analysis, conductance, IR and electronic spectra, magnetic moments, ¹H NMR and TG-DSC measurements as well as by mass spectroscopy. The use of BHP as analytical reagents for the determination of copper(II), nickel(II) and cobalt(II) as well as extracting agents for these metal ions are discussed.