Studies of densities, apparent molal volume, viscosities, surface tension and free energies of activation for interactions of praseodymium Sal 2en complex with dimethylsulphoxide

Abstract

Densities ( ρ, 10 − 3 kg m − 3 ), viscosities ( η, 10 − 1 kg m − 1 s − 1 ) and surface tension ( γ, mN m − 1 ) of 1 to 5 mg%/100 mL praseodymium (Pr) Sal 2en (N,N'-dihydroxybenzalethylene) complex at an interval of 1 mg%/100 mL with dimethylsulphoxide (DMSO) were studied at 293.15, 298.15 and 303.15 K temperatures. The ρ data are used for apparent molal volume ( V ϕ 10 − 6 m 3 mol − 1 ), η and γ calculations. The η values are fitted in the extended Jones–Dole equation ( η r − 1) / c vs c ( c = concentration) for coefficient B (kg L − 1 ) and slope D (kg L − 1 ) 2. The γ values are regressed against c for limiting surface tension ( γ 0) at infinite dilution ( c → 0). Similarly, limiting apparent molal volume ( V ϕ 0) or partial molal volumes ( V̄ 2 0) were derived from the V ϕ values for Pr complex interactions with DMSO. Partial molal volume ( V̄ 2 0) of DMSO was calculated from its ρ value. Free energies of activation of viscous flow (Δ μ 1 0⁎/kJ mol − 1 ) per mol of DMSO was calculated from its V̄ 2 0 and η 0 data and the Δ μ 2 0⁎ of Pr complex, from its B, V̄ 2 0 and V̄ 2 0 values. The free energy of activation for dropwise flow (Δ μ 2 0⁎surf) were evaluated from γ 0 values. The Δ μ 1 0⁎and Δ μ 2 0⁎ activation energies assess the structure making and breaking action of the Pr complex on DMSO. The coefficient B depicts a critical size of the Pr complex–DMSO interaction based on solute–solvent interaction theories and hence its values have been associated with transition state theory and explain positive transitions of interacting molecules. The ρ values at 293.15 and 303.15 K are higher than those of the DMSO with lower values at 298.15 K. The η values of DMSO are higher than those of the Pr complex. The Δ μ 1 0⁎ > 0 > Δ μ 2 0⁎ model of Δ μ 2 0⁎ defines the Pr complex–DMSO as nonideal systems with a huge shift in Δ μ 2 0⁎ values from DMSO to Pr complex.