Influence of Electrolytes on the Micellar Growth of Amphiphilic Drug Chlorpromazine Hydrochloride

The effect of electrolytes on the micellar behavior of an amphiphilic drug, chlorpromazine (CPZ) hydrochloride, was studied using cloud point (CP) and dye solubilization techniques. In the presence of KBr, increase in pH led to decrease in the CP of 50 mmol·L_-1 drug solution (prepared in 10 mmol·L_-1 sodium phosphate (SP) buffer) because of deprotonation of drug molecules at high pH. The visible absorbance increased (due to dye solubilization) with the increase in pH from 6.5 to 6.9, which indicated micellar growth. At fixed pH (6.7), addition of inorganic salts (KF, KCl, and KBr) to drug solutions (50 mmol·L_-1) caused an increase in the CP as well as in the visible absorbance, with effectiveness being in the order: F_- < Cl_- < Br_-. The results were discussed on the basis of counter-ion binding and their effect toward micellar growth. Cations (co-ions) also led to an increase in the CP (and also the visible absorbance), with their effectiveness order being Li₊ > Na₊ > K₊, which was explained by considering cognizance of their hydrated radii. Compared with anions, their effect was small. Increase in [CPZ] caused micellar growth and hence the CP as well as the visible absorbance increased. The overall behavior was discussed in terms of electrostatic interactions and micellar growth.     

The effect of physicochemical parameters on the separation recovery of plutonium and uranium from aqueous solutions by cation exchange

The effect of physicochemical parameters such as pH, salinity (e.g. [NaCl]) and competitive cation (e.g. Ca²⁺ and Fe³⁺) concentration on the separation recovery of plutonium and uranium from aqueous solutions by cation exchange has been investigated. The investigation was performed to evaluate the applicability of cation exchange as separation and pre-concentration method prior to the radiometric analysis of uranium and plutonium isotopes in natural water samples. Application of the method to test solutions of constant radionuclide concentration and variable composition (0.1, 0.5 and 1 M NaCl; 0.1 and 0.5 M Ca(NO₃)₂; 0.1 and 1 mM FeCl₃; 10) has generally shown that: (1) the optimum pH is 4.5 for uranium and plutonium, (2) increasing salinity results in slightly lower for uranium and significantly higher chemical recovery plutonium and (3) the presence of Ca(II) cations doesn’t significantly affect the chemical recovery of both radionuclides. Contrary, the presence of Fe(III) cations ([Fe(III)] > 0.1 mM) results in significantly lower chemical recovery for both radionuclides (<50%). The later is attributed to the formation of Fe(III) colloids, which present increased chemical affinity for uranium and plutonium and hence compete with the radionuclide binding by the resin. Nevertheless, the results indicate that the method could be successfully applied to a wide range of natural waters.     

The Effect of Added Salts and Organics on the Cloud Point of TX‐114

Herein we report the effect of additives (salts and organics) on the cloud point (CP) of nonionic surfactant Triton X‐114 (TX‐114) aqueous solutions. CP showed a concentration dependent variation in the absence of any added compound. Addition of quaternary ammonium (or phosphonium) bromides to 0.8 mM TX‐114 solutions increased the CP. It was found that long chain alcohols and amines decreased the CP of 0.8 mM TX‐114 +80 mM Bu₄AmB aqueous system, while it either remained constant or increased in the presence of short chain additives. The effect of first group additives (long chain) can be explained by considering that these additives solubilize in interfacial region and assist in micellar growth. Short chain additives remain in aqueous phase and affect the micelle hydration by affecting the solvent. Pentylamine behaved differently than pentanol: pentylamine increased the CP (like short chain additives) while pentanol decreased the CP. In pentylamine, the hydrophilicity of NH₂ group and its dissociation into NH₃ ⁺ dominates over the hydrophobicity of its alkyl chain. Aliphatic hydrocarbons first decreased and then increased the CP. The overall behavior depended upon the chain length of the hydrocarbon. With decane, the CP decreasing region disappeared completely.     

Study of the Cloud Point of the Phenothiazine Drug Chlorpromazine Hydrochloride: Effect of Surfactants and Polymers

Surfactants/polymers are used extensively in drug delivery as drug carriers. We herein report the effect of surfactants and polymers on the cloud point (CP) of amphiphilic drug chlorpromazine hydrochloride. At fixed drug concentration (50 mM) and pH (6.7) these additives affect the CP in accordance to their nature and structure: anionic surfactants show an increase followed by a decrease, whereas cationic (conventional as well as gemini) and nonionic surfactants show continous increase. The behavior with polymers is dictated by the number of units present in a particular polymer. Increase in drug concentration and pH, in presence of fixed amounts of CTAB, increases and decreases the CP, respectively. Variation of CP with pH at various fixed gemini concentrations shows that gemini surfactants are better candidates for drug delivery.     

The Micellization and Clouding Phenomena of a Nonionic Surfactant,Poly(ethylene glycol) t-octylphenyl ether (Triton X-100): Effect of (Chloride Salt) Electrolytes

Herein, we report the micellization and the clouding of a nonionic surfactant, poly(ethylene glycol) t-octylphenyl ether (Triton X-100), in aqueous solutions in the absence and presence of (chloride salt) electrolytes. In the absence and presence of electrolytes, the critical micelle concentration (CMC) of Triton X-100 was measured by surface tension measurements. Upon increasing the temperature as well as the concentration of electrolytes, the CMCs decreased. The surface properties and the thermodynamic parameters of the micellar systems were evaluated. From these evaluated thermodynamic parameters, it was found that in the presence of an electrolyte, the stability of the micellar system is high. The cloud points (CPs) of Triton X-100 were also measured in the absence and presence of metallic ions of electrolytes. Upon the addition of metallic ions of chloride salts (electrolytes), the decrease in CP values was observed and the order was found to be: K⁺ > Na⁺ > Li⁺ > NH⁺₄.     

Influence of organic additives on the clouding phenomena of promethazine hydrochloride solutions

This paper reports the influence of organic additives (alcohols, amino acids, sugars) on the micellization and cloud point (CP) of a phenothiazine drug, promethazine hydrochloride (PMT). The critical micelle concentration (CMC) of the drug, determined by surface tension measurements in the presence of a representative of each additive class (i.e., butanol, leucine, arabinose), are used to evaluate the maximum surface excess concentration (Γ _max) and the minimum area per surfactant molecule (A _min) at the air/water interface. Γ _max increases and CMC/A _min decreases with increasing concentration of the additives, which indicate mixed micelle formation. The intermicellar interaction coefficients in the mixed micelles (β ^m and β ^σ are also calculated, and their negative values imply attractive interactions. Effect of pH revealed CP decrease with increasing pH due to deprotonation of PMT molecules. Effect of amino acids depended upon their nature and polarity, whereas sugars caused a CP decreasing effect. Aliphatic alcohols as well as cycloalkanols and diols decreased the CP. In the presence of arabinose, increase in drug concentration resulted in the CP increase, while increase in pH showed an opposite trend. Results are interpreted on the basis of mixed micelle formation, hydrophobic interactions, and change in solvent structure.     

Synergistic extraction of some univalent cations into nitrobenzene by using cesium dicarbollylcobaltate and dibenzo-30-crown-10

From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium M⁺(aq) + 1·Cs⁺(nb) ? 1·M⁺(nb) + Cs⁺(aq) taking place in the two-phase water–nitrobenzene system (M⁺ = Li⁺, Na⁺, H⁺, NH₄ ⁺, Ag⁺, K⁺, Rb⁺, Tl⁺; 1 = dibenzo-30-crown-10; aq = aqueous phase, nb = nitrobenzene phase) were determined. Furthermore, the stability constants of the 1·M⁺ complexes in water-saturated nitrobenzene were calculated; they were found to increase in the series of Cs⁺ < H⁺, Ag⁺ < NH₄ ⁺ < Na⁺ < Rb⁺ < Li⁺ < K⁺, Tl⁺.     

Solvent extraction of Li+, H3O+ and NH4 + into nitrobenzene by using sodium dicarbollylcobaltate and calix[4]arene-bis(t-octylbenzo-18-crown-6)

From extraction experiments and $ \gamma $ -activity measurements, the exchange extraction constants corresponding to the general equilibrium M⁺ (aq) + NaL⁺ (nb) ? ML⁺ (nb) + Na⁺ (aq) taking place in the two–phase water–nitrobenzene system (M⁺= Li⁺, H₃O⁺, NH₄ ⁺; L = calix[4]arene-bis(t-octylbenzo-18-crown-6); aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Furthermore, the stability constants of the ML⁺ complexes in nitrobenzene saturated with water were calculated; they were found to increase in the following cation order: H₃O⁺ < Li⁺ < NH₄ ⁺.     

Biosorption of strontium from aqueous solutions onto spent coffee grounds

A set of experiments was carried out to evaluate the strontium uptake potential of spent coffee grounds (SCG) by batch tests in aqueous medium. Adsorption of Sr²⁺ as a function of contact time and adsorbent dose, pH, particles size, agitation speed, temperature and co-ions presence was investigated. Obtained results revealed that the maximum adsorption took place at pH range of 5–8 and temperature values between 283 and 333 K. Particles size effect was not very significant and agitation speed influenced on the equilibrium time. Competitive adsorption experiments allowed us to classify the negative effect on the Sr²⁺ uptake according to this order Al³⁺ ? Co²⁺ > Mg²⁺ > Ca²⁺ ? Na⁺ > K⁺ > Cs⁺. Kinetic study indicated that the Sr²⁺ uptake was fast and it was well fitted by the pseudo second order reaction model. Adsorption isotherm was well interpreted by Langmuir model. The maximum adsorption capacity was found to be 69.01 mg g^?1 at pH 7, 293 K, particles sizes = 200–400 μm and agitation speed 250 rpm. The thermodynamic study revealed that the process was spontaneous (ΔG ⁰ < 0), exothermic (ΔH ⁰ < 0) with a raised affinity for Sr²⁺ (ΔG ⁰ < 0, ΔS ⁰ > 0) and occurred by physical adsorption (E _a = 8.37 kJ mol^?1). FTIR analysis showed carboxylic acid and amino group presence on SCG surface playing a vital role in Sr²⁺ biosorption.     

Extraction of some univalent cations into phenyltrifluoromethyl sulfone by using sodium dicarbollylcobaltate in the presence of benzo-18-crown-6

From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium M⁺ (aq) + 1·Na⁺ (org) $ \Leftrightarrow $ 1·M⁺ (org) + Na⁺ (aq) taking place in the two-phase water–phenyltrifluoromethyl sulfone (abbrev. FS 13) system (M⁺ = Li⁺, H₃O⁺, NH₄ ⁺, Ag⁺, Tl⁺, K⁺, Rb⁺, Cs⁺; 1 = benzo-18-crown-6; aq = aqueous phase, org = FS 13 phase) were evaluated. Further, the stability constants of the 1·M⁺ complexes in FS 13 saturated with water were calculated; they were found to increase in the series of $ {\text{Cs}}^{ + } \, < \,{\text{Rb}}^{ + } \, < \,{\text{H}}_{ 3} {\text{O}}^{ + } \, < \,{\text{Ag}}^{ + } \, < \,{\text{Li}}^{ + } \, < \,{\text{NH}}_{4}^{ + } \, < \,{\text{K}}^{ + } \, < \,{\text{Tl}}^{ + } $ .     

Stability and Detergent Compatibility of a Predominantly β-Sheet Serine Protease from Halotolerant B. aquimaris VITP4 Strain

The present study deals with the characterization of halotolerant protease produced by Bacillus aquimaris VITP4 strain isolated from Kumta coast, Karnataka, India. The studies were performed at 40 °C and pH 8 in Tris buffer. Metal ions such as Mn²⁺ and Ca²⁺ increased the proteolytic activity of the enzyme by 34 and 30 %, respectively, at 10 mM concentration. Cu²⁺ at 1 mM concentration was found to enhance the enzyme activity by 16 %, whereas inhibition was observed at higher concentration (>5 mM). Slight inhibition was observed even with lower (>1 mM) concentrations of Zn²⁺, Hg²⁺, Fe³⁺, Ni²⁺, and Co²⁺.The activity of protease was completely inhibited by phenylmethylsulfonyl fluoride, indicating that the VITP4 protease is a serine protease. The presence of ethylenediaminetetraacetic acid and 1,10-phenanthroline (>5 mM) moderately inhibited the activity, suggesting that the enzyme is activated by metal ions. The protease was purified to homogeneity with a purification fold of 15.7 with ammonium sulfate precipitation and 46.65 with gel filtration chromatography using Sephadex G-100, resulting in a specific activity of 424?±?2.6 U mg^?1. The VITP4 protease consists of a single polypeptide chain with a molecular mass of 34.7 kDa as determined by sodium dodecyl sulfate–polyacrylamide gel electrophoresis and matrix-assisted laser desorption/ionization–time of flight. Among the different substrates used (casein, egg albumin, gelatin, and bovine serum albumin), the activity was higher with casein with V _max, K _m, and k _cat values of 0.817 mg ml min^?1, 0.472 mg ml^?1, and 2.31 s^?1, respectively. Circular dichroism studies revealed that the VITP4 protease has a predominantly β-sheet structure (51.6 %) with a temperature for half denaturation of 85.8 °C in the presence of 1 mM CaCl₂. Additionally, the VITP4 protease was found to retain more than 70 % activity in the presence of 10 mM concentration of different detergents (CTAB, urea, and sodium dodecyl sulfate) and surfactants (Triton X-100, Tween-20, and Tween-80), and the results of wash performance test with various commercial detergents confirmed that it can be used in detergent formulations.     

Oil-Water Partitioning of a Synthetic Tetracarboxylic Acid as a Function of pH

The oil-water partitioning of a synthetic tetraacid acting as a model compound for indigenous C₈₀-C₈₂ ARN acids has been studied as a function of pH, ionic strength and type of monovalent counterion. Experimental data obtained with ultraviolet-visible and HPLC/UV analyses have been fitted to thermodynamic models based on one, two or four dissociation steps to obtain o/w partition coefficients (K _wo ) of the fully protonated acid between chloroform and aqueous solutions, and its apparent acidity constant(s), pK _a. As the study is conducted above the CMC of the tetraacid, in general high apparent acidity constants were obtained in the range from 6 to 8 resulting from micellization equilibria. K _wo values were obtained in the range from 10^?3 to 10^?4, and decreasing with increasing salinity. At 50 mM K⁺, no conclusions could be made regarding the number of distinguishable dissociation steps, while at higher ionic strength (184 mM and 452 mM K⁺) and at 184 mM Na⁺ a model with two dissociation steps provided good fits to the experimental data. The first step was found to be given by a pK _a ≈ 6.6–6.8 and the second dissociation step at pK _a values ≈ 7.8–8.3. The two-step mechanism supports previous results obtained by potentiometric titrations. No significant difference in the o/w behavior was observed when changing the counterion from potassium to sodium. The main partitioning of the tetraacid in the aqueous phase occurred above pH 8, where the fully deprotonated acid was formed.     

A Convenient Approach to Simultaneous Analysis of a Pharmaceutical Drug and Its Counter-Ion by CE Using Dual-Opposite End Injection and Contactless Conductivity Detection

Capillary electrophoresis (CE) coupled to a capacitively coupled contactless conductivity detector (C⁴D) was used for the determination in a single analysis of a pharmaceutical drug and its counter-ion. Dual-opposite end injection (DOI) was used to introduce hydrodynamically the analytes at each end of the capillary. No modification of the commercial apparatus is required. After applying the voltage, the cations and anions migrate from each end of the capillary in opposite directions toward the detector placed near the cathode outlet. The electrophoretic conditions were initially developed with three test drugs (chlorpheniramine maleate, metoprolol tartrate, clomiphene citrate) and then applied to two Vinca alkaloids (catharanthine sulfate, vinorelbine ditartrate). The 10 mM histidine–50 mM acetic acid buffer (pH 4.1)–methanol 90:10 (v/v) electrolyte was suitable for the analysis of these high or medium mobile anions by CE–C⁴D due to its low conductivity background and high buffer capacity. Finally, the CE procedure developed was successfully validated for catharanthine sulfate. The method developed herein is fast (<10 min) and accurate (repeatability on migration time < 0.6% and peak areas < 1.3%, n = 6).

     

Monolithic ODS-silica gel column for determination of hydrogen, sodium, ammonium and potassium in acid rain by lon chromatography

Summary A monolithic ODS-silica gel column modified by saturating it with lithium dodecylsulfate (Li-DS) was firstly used to separate monovalent cations simultaneously including H⁺, Na⁺, NH₄ ⁺ and K⁺ by ion-chromatography (IC). Using an acidified 60 mM LiCl solution (pH 3.95, containing 0.10 mM Li-DS) as eluent, these monovalent cations were separated well in the order of Na⁺<NH₄ ⁺<K⁺<H⁺ within 3 min at a flow rate of 2.0 mL min⁻¹. The detection limits of these cations by this method with conductivity detection were 20.0 μM for Na⁺, 12.0 μM for NH₄ ⁺, 9.84 μM for K⁺ and 6.20 μM for H⁺. Acid rain water samples with a pH value less than 5.00 could be analyzed directly with this IC system.     

Sorption of uranyl ion on hydrous silica: Effects of ionic strength and ethylenediaminetetraacetic acid (EDTA)

The effects of ionic strength and of ethylenediamin et etraacetic acid (EDTA) on the sorption of uranyl ion, UO₂ ²⁺, to SiO₂·xH₂O (silica gel) were investigated. It was observed that pH and the ions present in the supporting electrolytes influence the ionic strength effects. The presence of different sodium salts in the concentration range (0.20 to 1.40M) suppressed the sorption of UO₂ ²⁺ in the order: NaNO₃ < NaClO₄ < NaCl < NaOCOCH₃ < Na₂SO₄ [pH 2.75(±0.05)], while the presence of perchlorate salts of Li⁺, Na⁺ and Ca²⁺ (0.20 to 1.40M) promoted the sorption of UO₂ ²⁺ on silica gel in the order: LiClO₄∼NaClO₄<Ca(ClO₄)₂ at pH 2.80(±0.05). The ionic strength effect on UO₂ ²⁺ sorption was studied in presence of EDTA (0–1.00·10⁻³M) in the pH range 2.90 to 5.57. The sorption data and speciation calculation suggest negligible complexation of UO₂ ²⁺ with EDTA at I≥1.00M NaClO₄. On leave from Radiochemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai, 400 085, India.     

Solvent extraction of cesium into nitrobenzene by using sodium,potassium and rubidium dicarbollylcobaltates in the presence of polypropylene glycol PPG 425

Extraction of microamounts of cesium by nitrobenzene solutions of sodium dicarbollylcobaltate (Na⁺B^?), potassium dicarbollylcobaltate (K⁺B^?) and rubidium dicarbollylcobaltate (Rb⁺B^?) in the presence of polypropylene glycol PPG 425 (L) has been investigated. The equilibrium data have been explained assuming that the complex species ML⁺ (M⁺ = Na⁺, K⁺, Rb⁺, Cs⁺; L = PPG 425) are present in the organic phase. The stability constants of the cationic complex species ML⁺ (M⁺ = Na⁺, K⁺, Rb⁺) in nitrobenzene saturated with water have been determined; they were found to increase in the series of Rb⁺ < K⁺ < Na⁺.     

A Highly K+‐Selective Two‐Photon Fluorescent Probe

A highly K⁺‐selective two‐photon fluorescent probe for the in vitro monitoring of physiological K⁺ levels in the range of 1–100 mM is reported. The two‐photon excited fluorescence (TPEF) probe shows a fluorescence enhancement (FE) by a factor of about three in the presence of 160 mM K⁺, independently of one‐photon (OP, 430 nm) or two‐photon (TP, 860 nm) excitation and comparable K⁺‐induced FEs in the presence of competitive Na⁺ ions. The estimated dissociation constant (K_d) values in Na⁺‐free solutions (K_d^OP=(28±5) mM and K_d^TP=(36±6) mM ) and in combined K⁺/Na⁺ solutions (K_d^OP=(38±8) mM and K_d^TP=(46±25) mM ) reflecting the high K⁺/Na⁺ selectivity of the fluorescent probe. The TP absorption cross‐section (σ_2PA) of the TPEF probe+160 mM K⁺ is 26 GM at 860 nm. Therefore, the TPEF probe is a suitable tool for the in vitro determination of K⁺.     

Complexation of some univalent organic cations with hexaethyl p-tert-butylcalix[6]arene hexaacetate in nitrobenzene saturated water

From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium C⁺(aq) + 1·Cs⁺(nb) ?1·C⁺ (nb) + Cs⁺(aq) taking place in the two–phase water–nitrobenzene system (C⁺ = methylammonium, ethylammonium, propylammonium, ethanolammonium, diethanolammonium, triethanolammonium, protonated tyramine, protonated dopamine, protonated DL–noradrenaline; 1 = hexaethyl p-tert-butylcalix[6]arene hexaacetate; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Furthermore, the stability constants of the 1·C⁺ complex species in nitrobenzene saturated with water were calculated; they were found to increase in the following cation order: protonated tyramine < protonated dopamine < triethanolammonium < diethanolammonium < protonated DL-noradrenaline < propylammonium < ethanolammonium < ethylammonium < methylammonium.     

Kinetics and mechanism of the substitution reactions of some monofunctional Pt(II) complexes with heterocyclic nitrogen donor molecules. Crystal structure of [Pt(bpma)(pzBr)]Cl2·2H2O

Substitution reactions of [Pt(terpy)Cl]⁺ (terpy = 2,2′;6′,2′′-terpyridine), [Pt(bpma)Cl]⁺ (bpma = bis(2-pyridylmethyl)amine), [Pt(dien)Cl]⁺ (dien = diethylenetriamine or 1,5-diamino-3-azapentane) and [Pt(tpdm)Cl]⁺ (tpdm = tripyridinedimethane) with nitrogen donor heterocyclic molecules, such as 3-amino-4-iodo-pyrazole (pzI), 5-amino-4-bromo-3-methyl-pyrazole (pzBr) and imidazole (Im), were studied in aqueous 0.10 M NaClO₄ in the presence of 10 mM NaCl using variable-temperature UV–vis spectrophotometry. The second-order rate constants k₂ indicate decrease in reactivity in the order [Pt(terpy)Cl]⁺ > [Pt(bpma)Cl]⁺ > [Pt(tpdm)Cl]⁺ > [Pt(dien)Cl]⁺. The most reactive nucleophile among the heterocyclic compounds is imidazole, while pzI shows slightly higher reactivity than pzBr. Activation parameters were also determined and the negative values for entropies of activation, ΔS^≠, support an associative mode of substitution for all substitution processes. Crystal structure of [Pt(bpma)(pzBr)]Cl₂·2H₂O was determined by single-crystal X-ray analysis. The coordination geometry of the complex is distorted square-planar while the bond distance Pt–N2(pzBr) is longer than the other three Pt–N distances.     

Kinetics and mechanism of the substitution reactions of some monofunctional Pd(II) complexes with different nitrogen-donor heterocycles

Substitution reactions of five monofunctional Pd(II) complexes, [Pd(terpy)Cl]⁺ (terpy = 2,2′;6′,2″-terpyridine), [Pd(bpma)Cl]⁺ (bpma = bis(2-pyridylmethyl)amine), [Pd(dien)Cl]⁺ (dien = diethylenetriamine or 1,5-diamino-3-azapentane), [Pd(Me₄dien)Cl]⁺ (Me₄dien = 1,1,7,7-tetramethyldiethylenetriamine), and [Pd(Et₄dien)Cl]⁺ (Et₄dien = 1,1,7,7-tetraethyldiethylenetriamine), with unsaturated N-heterocycles such as 3-amino-4-iodo-pyrazole (pzI), 5-amino-4-bromo-3-methyl-pyrazole (pzBr), 1,2,4-triazole, pyrazole, pyrazine, and imidazole were investigated in aqueous 0.10 M NaClO₄ in the presence of 10 mM NaCl using variable-temperature stopped-flow spectrophotometry. The second-order rate constants k₂ indicate that the reactivity of the Pd(II) complexes decrease in the order [Pd(terpy)Cl]⁺ > [Pd(bpma)Cl]⁺ > [Pd(dien)Cl]⁺ > [Pd(Me₄dien)Cl]⁺ > [Pd(Et₄dien)Cl]⁺. The most reactive nucleophile of the heterocycles is pyrazine, while the slowest reactivity is with pyrazole. Activation parameters were determined for all reactions and negative entropies of activation, ΔS^≠, supporting an associative mode of substitution. The reactions between [Pd(bpma)Cl]⁺ and 1,2,4-triazole, pzI, and pzBr were also investigated by ¹H NMR to define the manner of coordination. These results could be useful for better explanation of structure-reactivity relationships of Pd(II) complexes as well as for the prediction of potential targets of Pd(II) complexes toward common N-heterocycles, constituents of biomolecules and different N-bonding pharmaceutical agents.