Synthesis,structure, and magnetic properties of a hexanuclear manganese complex

The reaction of 1-(2-pyridyl)-3-(p-tolyl)propane-1,3-dione (HL) with [Mn₃O(O₂CPh)₆(H₂O)(py)₂] in CH₂Cl₂ affords a mixed-valence ${\mathrm{Mn}}_3^{\text{II}}{\mathrm{Mn}}_3^{\text{III}}$ hexanuclear complex [Mn₆O₂(O₂CPh)₈L₃] (1). Complex 1 contains a $[{\mathrm{Mn}}_3^{\text{II}}{\mathrm{Mn}}_3^{\text{III}}({\mathrm{\mu }}_4\text{-}\mathrm{O}{)}_2{]}^{11+}$ core, which is a new structural type in the family of Mn₆ complexes. Variable temperature magnetic susceptibility and magnetization measurement of complex 1 have been carried out. The magnetic data indicate that complex 1 has a ground state spin value of S = 7/2 with significant magnetoanisotropy as gauged by the D value of −0.46 cm⁻¹. The frequency dependence of the out-of-phase component in alternating current magnetic susceptibilities for complex 1 indicates the slow magnetic relaxation of a superparamagnetic molecule.     

Determination of activity coefficients at infinite dilution of water and organic solutes (polar and non-polar) in the Ammoeng 100 ionic liquid at T = (308.15, 313.5, 323.15, and 333.15) K

Activity coefficients at infinite dilution $({\gamma }_{13}^{\infty })$ have been determined for 27 solutes, viz. water and organic compounds (n-alkanes, cycloalkanes, 1-alkenes, 1-alkynes, aromatics, alcohols, and ketones) in the ionic liquid Ammoeng 100, by gas–liquid chromatography at four different temperatures, T = (308.15, 313.15, 323.15, and 333.15) K. Columns with different phase loadings (20 to 24)% of the ionic liquid in the stationary phase were employed to obtain ${\gamma }_{13}^{\infty }$ values at each temperature investigated. Partial molar excess enthalpies at infinite dilution ($\mathrm{\Delta }{H}_1^{E\text{,}\infty }$) were calculated for the solutes from the temperature dependency relationship of the $\ln ({\gamma }_{13}^{\infty })$ values for the temperature range in this study. The uncertainties in the determinations of the ${\gamma }_{13}^{\infty }$ and $\mathrm{\Delta }{H}_1^{E\text{,}\infty }$ values are 6% and 10%, respectively. Selectivity values at infinite dilution ($S_{\mathit{ij}}^{\infty }$), have been computed from the ${\gamma }_{13}^{\infty }$ values to assess the potential candidacy of the Ammoeng 100 ionic liquid for the separation of alkane/alcohol mixtures. The results from this study have been compared to those available for several ionic liquids from previous investigations.     

Partial molar volume and partial molar compressibility of four homologous α-amino acids in aqueous sodium fluoride solutions at different temperatures

Density and ultrasonic speed of four amino acids (glycine, l-alanine, l-valine, and l-leucine) in aqueous sodium fluoride solutions {(0.1 to 0.5) M} have been measured at T = (308.15, 313.15, and 318.15) K. Apparent molar volumes (V_φ), partial molar volumes $\left(V_{\phi }^0\right)$, transfer volumes $\left(\mathrm{\Delta }{V}_{\phi }^0\right)$ and hydration number (n_H) are evaluated using density data. Adiabatic compressibility (β_s), change (Δβ_s), and relative change in compressibility (Δβ_s/β₀), apparent molar compressibility (K_φ), partial molar compressibility $\left(K_{\phi }^0\right)$, transfer compressibility $\left(\mathrm{\Delta }{K}_{\phi }^0\right)$, and hydration number (n_H) have been calculated using ultrasonic speed data. The linear correlation of $V_{\phi }^0\text{,}\mathrm{\Delta }{V}_{\phi }^0\text{,}{K}_{\phi }^0$ and $\mathrm{\Delta }{K}_{\phi }^0$ for a homologous series of amino acids have been used utilised to calculate the contribution of charged end groups (${\text{NH}}_3^{+}$, COO^?), CH₂ group and other alkyl chain of the amino acids. The analysis shows that the ion–ion interactions are much stronger than ion–hydrophobic interactions over the entire concentration range of sodium fluoride. It is observed that sodium fluoride has a strong dehydration effect on amino acids.