Studies of densities, apparent molal volume, viscosities, surface tension and free energies of activation for interactions of praseodymium Sal2en complex with dimethylsulphoxide

Densities (ρ, 10− 3kg m− 3), viscosities (η, 10− 1kg m− 1 s− 1) and surface tension (γ, mN m− 1) of 1 to 5 mg%/100 mL praseodymium (Pr) Sal2en (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 (Vϕ 10− 6m3 mol− 1), η and γ calculations. The η values are fitted in the extended Jones-Dole equation (ηr − 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 (γ0) at infinite dilution (c → 0). Similarly, limiting apparent molal volume (Vϕ0) or partial molal volumes (V̄20) were derived from the Vϕ values for Pr complex interactions with DMSO. Partial molal volume (V̄20) of DMSO was calculated from its ρ value. Free energies of activation of viscous flow (Δμ10⁎/kJ mol− 1) per mol of DMSO was calculated from its V̄20 and η0 data and the Δμ20⁎ of Pr complex, from its B, V̄20 and V̄20 values. The free energy of activation for dropwise flow (Δμ20⁎surf) were evaluated from γ0 values. The Δμ10⁎and Δμ20⁎ 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 Δμ10⁎ > 0 > Δμ20⁎ model of Δμ20⁎ defines the Pr complex-DMSO as nonideal systems with a huge shift in Δμ20⁎ values from DMSO to Pr complex.