Journal of Applied Organometallic Chemistry
Volume:4 Issue: 1, Jan 2024

Alkaline hydrolysis of phosphate diester compounds with a common leaving group (LG) and varying non-leaving groups (NLG) was investigated. The nitrophenyl group was employed as a leaving group due to its favorable leaving group properties, significant absorbance for reaction monitoring, and selective cleavage of the phosphorus-oxygen bond, which is relevant for DNA and RNA degradation. Reactions were conducted under pseudo first-order conditions in NaOH solutions 70 °C. In addition, the alkaline hydrolysis was studied using a 1M NaOH solution at different temperatures (50–80 °C), pH (12-14) levels, and viscosities (with 0% - 40% glycerol). Reaction progress was continuously monitored by measuring the absorbance increase of the 4-nitrophenolate ion at λ = 400 nm. The rate constant (kobs) was determined by fitting the data to a first-order equation. The results demonstrate kobs increased with higher NaOH concentration, temperature, pH, and solution viscosity, except for NppNPP. Investigation of the effect of the non-leaving group's pKa revealed slight sensitivity of the hydrolysis reaction with βNLG = -0.12. Thermodynamic parameters were determined and the values were as follows: ∆H = 48.8 kJ.mol-1, ∆S = -171.6 J.mol-1.K-1, ∆G = 99.9 kJ.mol-1 for BpNPP; ∆H = 64.9 kJ.mol-1, ∆S = -127.1 J.mol-1.K-1, ∆G = 102.8 kJ.mol-1 for PypNPP; ∆H = 86.3 kJ.mol-1, ∆S = -76.7 J.mol-1.K-1, ∆G = 109.2 kJ.mol-1 for MpNPP, and ∆H = 63.7 kJ.mol-1, ∆S = -152 J.mol-1.K-1, and ∆G = 109 k kJ.mol-1 for NppNPP. All four hydrolysis processes have positive ∆G values, which means they are non-spontaneous and require external energy to proceed.

Manganese oxides have emerged as a focal point of extensive research due to their multifaceted roles in various scientific domains. This comprehensive review article delves into the diverse facets of manganese oxides, spanning from their crucial involvement in environmental geochemistry to their pivotal role in biogeochemical cycling. These minerals exhibit a broad spectrum of redox chemistry, from Mn(II) to Mn(IV) and Mn(VII), allowing them to partake in a variety of catalytic processes. The article explores the impact of pH on the stability and reactivity of different manganese species, illustrating the relevance of these compounds across the acidic to alkaline pH spectrum. Furthermore, it delves into their significance in advanced oxidation processes for water treatment, particularly the potent MnO4–/HSO3–  system. The article also unveils the pivotal role of manganese oxides in anion-exchange membrane fuel cells and electrolyzers as alternatives to noble metal catalysts for oxygen reduction and evolution reactions. Lastly, this review underscores the importance of understanding the thermodynamic stability of various manganese species under different conditions. It serves as a valuable resource for researchers and scientists exploring the multifaceted world of manganese oxides and their diverse applications across various scientific disciplines.

Characterizing the corrosion behavior of pipeline brasses undergoing cyclic temperature variation is essential for the prevention of degradation. Two brass alloys, (α+β)-brass and α-brass, were studied to evaluate their surfaces in drinking water at constant and cyclically varying temperatures. Both alloys were immersed for 1h in drinking water at nine different temperatures, starting at 278 K, and going up to 318 K. The two copper-zinc alloys were also immersed for 96 h at both critical temperatures (278 K and 318 K) and room temperature. To study the effect of cyclic temperature variation, immersion tests at cyclically varying temperatures were done between the two critical values for 4 cycles. The results of an integral electrochemical analysis using (PDP) and (EIS) revealed that the two alloys react differently under the same experimental conditions. The corrosion rate has approximate values for the cyclical temperature change of 3.04 µA cm-2 for α-brass and 3.26 µA cm-2 for (α+β)-brass. Impedance tests also show that α-brass tends to hold up remarkably well with 130.5 KΩ.cm² of polarization resistance versus 94.1 KΩ.cm² for (α+β)-brass. Similarly, degradation was observed in both alloys during cyclic temperature changes. The etched surfaces of the alloys were examined using SEM-EDX to obtain a clearer understanding of the surface morphology. The SEM images showed that an oxide film protects the surfaces. Monitoring of Cu2+ and Zn2+ ions in the electrolyte by ICP provided a detailed idea of the leaching of these metals.

This study focuses on investigating the complexation process between N,N'-bis(salicylidene)ethylenediamine (Salen) and the metal complex [Cu(PDTC)2] in a dimethyl sulfoxide (DMSO) solvent. The kinetics and thermodynamics of the substitution reaction were examined. The [Cu(PDTC)2] complex and the Salen ligand were synthesized using a reported method, and their absorption spectra displayed characteristic peaks consistent with previous findings. The kinetics of the Cu(II) complex were studied under pseudo-first-order conditions in DMSO, with varying concentrations of Salen and a constant concentration of the [Cu(PDTC)2] complex. Reactions were carried out at temperatures of 25 °C, 30 °C, and 35 °C. By conducting temperature-dependent studies, the activation parameters (activation energy, activation entropy, and activation enthalpy) were determined. The substitution reaction was monitored through absorption spectra measurements, revealing a reduction in the absorption peak at 435 nm and the appearance of a new absorption peak at 360 nm. The rate constants obtained for the substitution reactions of salen at 25 °C fell within the range of 0.16x10-1 1/min to 5.66x10-1 1/min, which was higher compared to previous investigations due to the size of the substituted ligand. The reaction was found to follow the first-order kinetics with respect to [Cu(PDTC)2] and salen, indicating a second-order overall reaction. Increasing temperature resulted in higher values of kobs and k2. The calculated activation parameters revealed a positive activation entropy, implying a dissociative mechanism, and a positive activation enthalpy, indicating an endothermic nature of the substitution reaction.

This study focused on optimizing the mechanical properties of ternary Al-Si-Cu alloys. Alloys near the eutectic composition (AS5U5, AS5U10, AS5U15, AS10U5, AS10U10, AS10U15, AS15U5, AS15U10, and AS15U15) were examined by melting and casting commercially pure metals (99.9% Al, 99.7% Si, and 99.9% Cu). Thermos-Calc software was used to analyze the precipitation phases and solidification process around the eutectic composition. Microstructural analysis, quantification of phases during solidification, and characterization using Scanning Electron Microscopy (SEM) with energy-dispersive X-ray analysis (EDX) were performed. Results revealed that the formation of the Al2Cu component was unaffected by silicon content, but as copper content increased, the percentage of precipitated Al2Cu increased, impacting the hardness of the alloys, especially at lower solidification temperatures.

Electronic absorption spectra, infrared spectroscopy, nuclear magnetic resonance, molar conductance, and elemental analysis are some of the physicochemical methods used to characterize the 4-chloro-N'-[(E)-(2,6-dihydroxy phenyl) methylidene] benzohydrazide (HBHDH) molecule that has been synthesized. The results of the analysis show that the metal and ligand formed a 1:2 ratio. According to the spectra, the ligand HBHDH forms tridentate coordination spheres with metal ions using an ONO bond. Complexes with Fe(II), Co(II), Ni(II), Cu(II), and Mn(II) have an octahedral shape because of this. In contrast to the tetrahedral structure of the complexes created with Zn(II), Cd(II), and Hg(II), the Pd(II) complex takes on a square planar layout. According to the molar conductance values in DMF, the complexes do not undergo electrolysis. It has been determined that the metal complexes and Schiff's base HBHDH ligand have antibacterial action. The antibacterial efficiency of each combination and ligand against E. coli bacteria is higher than that of regular streptomycin.Candida albicans (MCC 1439) and Saccharomyces cerevisiae (MCC 1033) have significant antifungal effectiveness, with their growth being inhibited by over 92% in the presence of Mn(II) and Fe(II) complexes, respectively.