Application of scaled particle theory to the partial molar volumes of some tetradentate N2O2 type Schiff bases in ionic liquid + DMF solutions

•The Salnaph, Salcn Schiff bases and ionic liquid were synthesized.•The densities of ‘Schiff base + ionic liquid + DMF’ mixtures were measured.•Volumetric parameters were calculated using the density data and interpreted in terms of scaled particle theory.•The results show that the polar–ionic and polar–polar interactions are dominant in these mixtures.

Two tetradentate N2O2 type Schiff bases, 8-amino-[1-(2-hydroxyphenyl)imino]naphthalene (Salnaph) and N,N-bis(salicylidene)-1,2-cyclohexadiamine (Salcn), have been synthesized and their densities in ionic liquid, 1-penthyl-3-methylimidazolium bromide ([PnMIm]Br) + N,N-dimethyl formamide (DMF) solutions measured at 298.15 K. These data have been used to calculate apparent molar volumes, VϕVϕ, standard partial molar volumes, Vϕ0, transfer partial molar volumes, ΔtrVϕ0, pair volumetric interaction parameters, VSIVSI, triplet volumetric interaction parameters, VSIIVSII, (calculated using McMillan Mayer theory) interaction volumes, VintVint, and cavity volumes, V¯cav, (calculated by use of scaled particle theory) for the solutions studied. All of these parameters were used to interpret the effect of ionic liquid on the solute–solvent interactions and solvation behavior occurring between ionic liquid and Schiff bases in these solutions in terms of scaled particle theory (SPT).