Mechanistic diversity covering 15 orders of magnitude in rates: cyanide exchange on [M(CN)(4)](2-) (M = Ni, Pd, and Pt)

Kinetic studies of cyanide exchange on [M(CN)(4)](2-) square-planar complexes (M = Pt, Pd, and Ni) were performed as a function of pH by (13)C NMR. The [Pt(CN)(4)](2-) complex has a purely second-order rate law, with CN(-) as acting as the nucleophile, with the following kinetic parameters: (k(2)(Pt,CN))(298) = 11 +/- 1 s(-1) mol(-1) kg, DeltaH(2) (Pt,CN) = 25.1 +/- 1 kJ mol(-1), DeltaS(2) (Pt,CN) = -142 +/- 4 J mol(-1) K(-1), and DeltaV(2) (Pt,CN) = -27 +/- 2 cm(3) mol(-1). The Pd(II) metal center has the same behavior down to pH 6. The kinetic parameters are as follows: (k(2)(Pd,CN))(298) = 82 +/- 2 s(-1) mol(-1) kg, DeltaH(2) (Pd,CN) = 23.5 +/- 1 kJ mol(-1), DeltaS(2) (Pd,CN) = -129 +/- 5 J mol(-1) K(-1), and DeltaV(2) (Pd,CN) = -22 +/- 2 cm(3) mol(-1). At low pH, the tetracyanopalladate is protonated (pK(a)(Pd(4,H)) = 3.0 +/- 0.3) to form [Pd(CN)(3)HCN](-). The rate law of the cyanide exchange on the protonated complex is also purely second order, with (k(2)(PdH,CN))(298) = (4.5 +/- 1.3) x 10(3) s(-1) mol(-1) kg. [Ni(CN)(4)](2-) is involved in various equilibrium reactions, such as the formation of [Ni(CN)(5)](3-), [Ni(CN)(3)HCN](-), and [Ni(CN)(2)(HCN)(2)] complexes. Our (13)C NMR measurements have allowed us to determine that the rate constant leading to the formation of [Ni(CN)(5)](3-) is k(2)(Ni(4),CN) = (2.3 +/- 0.1) x 10(6) s(-1) mol(-1) kg when the following activation parameters are used: DeltaH(2)() (Ni,CN) = 21.6 +/- 1 kJ mol(-1), DeltaS(2) (Ni,CN) = -51 +/- 7 J mol(-1) K(-1), and DeltaV(2) (Ni,CN) = -19 +/- 2 cm(3) mol(-1). The rate constant of the back reaction is k(-2)(Ni(4),CN) = 14 x 10(6) s(-1). The rate law pertaining to [Ni(CN)(2)(HCN)(2)] was found to be second order at pH 3.8, and the value of the rate constant is (k(2)(Ni(4,2H),CN))(298) = (63 +/- 15) x10(6) s(-1) mol(-1) kg when DeltaH(2) (Ni(4,2H),CN) = 47.3 +/- 1 kJ mol(-1), DeltaS(2) (Ni(4,2H),CN) = 63 +/- 3 J mol(-1) K(-1), and DeltaV(2) (Ni(4,2H),CN) = - 6 +/- 1 cm(3) mol(-1). The cyanide-exchange rate constant on [M(CN)(4)](2-) for Pt, Pd, and Ni increases in a 1:7:200 000 ratio. This trend is modified at low pH, and the palladium becomes 400 times more reactive than the platinum because of the formation of [Pd(CN)(3)HCN](-). For all cyanide exchanges on tetracyano complexes (A mechanism) and on their protonated forms (I/I(a) mechanisms), we have always observed a pure second-order rate law: first order for the complex and first order for CN(-). The nucleophilic attack by HCN or solvation by H(2)O is at least nine or six orders of magnitude slower, respectively than is nucleophilic attack by CN(-) for Pt(II), Pd(II), and Ni(II), respectively.     

Distorted five-fold coordination of Cu2+(aq) from a Car-Parrinello molecular dynamics simulation

The solvation shell structure and dynamics of a single Cu2+ ion in a periodic box with 32 water molecules under ambient conditions has been investigated using Car-Parrinello molecular dynamics simulations in a time-window of 18 ps. Five-fold coordination with four equidistant equatorial water molecules at 2.00 A and one axial water molecule at 2.45 A from the Cu2+ ion is found. A "hole" without water molecules is found on the opposite side of the axial water. The ion-water bonding character for the equatorial water molecules is different from that of the axial water molecules, as shown by a localized orbital analysis of the electronic structure. Moreover, the calculated OD stretching vibrational band for the equatorial water molecules lies ca. 175 cm-1 below the axial-water band, in good agreement with experimental data. The equatorial-water band lies below, and the axial-water band above, the pure liquid D2O band, also in agreement with experimental data.     

Thermochemistry and kinetics of the aspect of diammonium hydrogen phosphate precipitation in phosphoric acid solution

Journal of Thermal Analysis and Calorimetry - The thermochemical and kinetic studies of diammonium hydrogen phosphate precipitation in phosphoric acid with ammonia were followed using a...     

1,3-Dipolar Cycloaddition of Nitrones with 5-Methylenehydantoins: Synthesis and Transformation of New Spirohydantoin Derivatives

1,3-Dipolar cycloaddition of various acyclic nitrones with 5-methylenehydantoin derivatives afforded new chiral spiroadducts in good yields. All the spirohydantoins were obtained through a regio- and stereospecific pathway, and the spirocarbon atom was linked to the isoxazolidine oxygen atom. A representative example of the reduction of the spirohydantoin 8 with Zn/AcOH led to the substituted 1,3-aminoalcohol hydantoin 20.     

Synthesis and antitumor activity evaluation of some 1, 2, 4-triazine and fused triazine derivatives

Reactions of 3-hyrazino-5,6-diphenyl-1,2,4-triazine with various carbonyl compounds such as ethyl acetoacetate, acetylacetone, benzoin, isatin, phthalic anhydride, phenyl isocyanate and acetic anhydride were discussed. Its reactions with α, β unsaturated compounds such as arylidinemalononitrile, diethyl acetylenedicarboxylate, dibenzylidine hydrazine were studied. These reactions led to the formation of various triazine and fused-triazine derivatives. The antitumor activity of the synthesized compounds was tested against HePG2 and MCF-7 cell lines. Some of the tested compounds were most active, whereas other compounds exhibited little or no activity.     

Structural and optical characterizations of rare earth pentaphosphates LnP5O14 (Ln = La, Gd) synthesized by the sol–gel process

The sol–gel chemistry route has successfully been used to prepare samples of LnP₅O₁₄ (Ln = La, Gd) pentaphosphates from lanthanides chlorides and phosphorous pentoxide dissolved in isopropanol. Crystallized powders of single phase were obtained after calcination of gels at 350 °C. The structural characterizations of materials were investigated by means of X-ray diffraction as well as infrared and Raman spectroscopies, whereas their thermal behavior has been studied by differential thermal analyse and thermogravimetric analyses. Powders morphology was analyzed by means of scanning electron microscopy and laser granulometry. The photoluminescence properties of the Eu³⁺ ions in sol–gel derived LaP₅O₁₄ and GdP₅O₁₄ samples were investigated and compared with homologous samples synthesized by the conventional solid state reaction.     

Effects of mussel-inspired co-deposition of 2-hydroxymethyl methacrylate and poly (2-methoxyethyl acrylate) on the hydrophilicity and binding tendency of common hemodialysis membranes: Molecular dynamics simulations and molecular docking studies

Despite advances in the field, hemoincompatibility remains a critical issue for hemodialysis (HD) as interactions between various human blood constituents and the polymeric structure of HD membranes results in complications such as activation of immune system cascades. Adding hydrophilic polymer structures to the membranes is one modification approach that can decrease the extent of protein adsorption. This study conducted molecular dynamics (MD) simulations to understand the interactions between three human serum proteins (fibrinogen [FB], human serum albumin, and transferrin) and common HD membranes in untreated and modified forms. Poly(aryl ether sulfone) (PAES) and cellulose triacetate were used as the common dialyzer polymers, and membrane modifications were performed with 2-hydroxymethyl methacrylate (HEMA) and poly (2-methoxyethyl acrylate) (PMEA), using polydopamine-assisted co-deposition. The MD simulations were used as the framework for binding energy simulations, and molecular docking simulations were also performed to conduct molecular-level investigations between the two modifying polymers (HEMA and PMEA) and FB. Each of the three proteins acted differently with the membranes due to their unique nature and surface chemistry. The simulations show PMEA binds less intensively to FB with a higher number of hydrogen bonds, which reflects PMEA's superior performance compared to HEMA. The simulations suggest PAES membranes could be used in modified forms for blood-contact applications as they reflect the lowest binding energy to blood proteins.     

Voltammetric Analysis of Oxymetazoline Hydrochloride at Zeolite – Modified Carbon Paste Electrode in Micellar Medium

Simple, sensitive, accurate and inexpensive differential pulse (DPV) and square wave (SWV) voltammetric methods utilizing zeolite modified carbon paste electrode (ZMCPE) were developed for the determination of Oxymetazoline hydrochloride (OXM) in nasal drops. Various experimental parameters were optimized using cyclic voltammetry (CV). Calibration curves were linear over the concentration ranges 9.8×10⁻⁸–3.6×10⁻⁶ M and 9.8×10⁻⁶–9×10⁻⁵ M for DPV and SWV, respectively. The DPV method showed a limit of detection (LOD) of 1.04×10⁻⁷ M. The method was applied for the determination of OXM in pharmaceutical formulation with an average recovery of 101.18 % (%RSD=0.41, n=9).     

Synthesis of diverse novel compounds with anticipated antitumor activities starting with biphenyl chalcone

The chalcone as (E)-1-([1,1′-biphenyl]-4-yl)-3-(3,4-dimethoxyphenyl)prop-2-en-1-one ( 3 ) was reacted with various active methylene compounds via Michael addition reaction under different conditions. In one hand, chalcone 3 reacted with isatin and glycine in one pot reaction via 1,3-dipolar cycloaddition reaction. On the other hand, chalcone 3 was also reacted with different N-nucleophiles via direct addition on the carbonyl group to award cyclic and/or acyclic products. Meanwhile, the reaction of chalcone 3 with S-benzylthiuronium chloride afforded the thio-Michael addition product. Chalcone 3 and 10 novel synthesized compounds were screened against two cell lines (HepG2 and MCF-7). Among of them, thiosemicarbazone 16 , oxime 14 and pyrimidine-2(1H)-thione 19 derivatives revealed an excellent activity against both cell lines (IC₅₀ values = 6.79-12.91 μM), whereas thiosemicarbazone 16 (6.79 ± 0.5 and 7.58 ± 0.6 μM) showed the highest activity.     

Nano nickel [1,2,4]-triazole-3-thiones complex: Design,sonochemical synthesis,and antimicrobial evaluation

A series of new 1,2,4-triazole-3-thiones were synthesized by calm, benign, no risk, eco-friendly, and energy efficient sequential reaction methodology like grinding and ultrasonic (US). In addition, 1,2,4-triazoles were prepared under conventional method and comparative study was done. The synthesized 1,2,4-triazoles were complexed with Ni(II) to produce nanoparticles complexes (NPC's) with average particle size vary from 55 to 100 nm (using scanning electron microscope technique) with good yields via both US and conventional techniques. X-ray diffraction technique and spectra analysis techniques were used to confirm the square planer geometry of the synthesized NPC's. Antimicrobial activity of the prepared 1,2,4-triazoles and their nickel complexes were studied which evaluated a high activity with complexes instead their triazoles.