Effect of ionic liquid on the solvation behavior of nonaqueous N,N 0 -salicylidenephenylediamine Schiff base (Salophen) solutions at 298.15 K Hemayat Shekaari a,⇑ , Rasoul Elhami-Kalvanagh b , Abolfazl Bezaatpour c a Department of Physical Chemistry, University of Tabriz, Tabriz, Iran b Department of Chemistry, Mamaghan Branch, Islamic Azad University, Mamaghan, Iran c Department of Chemistry, University of Mohaghegh Ardabili, Ardabil, Iran article info Article history: Received 28 November 2012 Received in revised form 19 April 2013 Accepted 25 April 2013 Available online 6 May 2013 Keywords: Salophen Schiff base Ionic liquid Thermodynamic properties Organic solvents abstract Thermodynamic properties of N,N 0 -salicylidenephenylediamine Schiff base (Salophen) in the solutions of ionic liquid, 1-butyl-3-methylimidazolium bromide ([BMIm]Br) + organic solvents (N,N-dimethylacet- amide DMA, and dimethylsulfoxide DMSO) have been measured at 298.15 K. The measured density and viscosity values have been used to calculate apparent molar volumes, V / , standard partial molar volumes, V 0 / , standard partial molar volumes of transfer, D tr V 0 / , viscosity B-coefficients, and solvation numbers, B=V 0 / , for the solutions being studied. All of these parameters were used to interpret the sol- ute–solvent interactions and solvation process occurring between ionic liquid and Salophen. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Schiff bases or imines, R 2 C = NR, are the condensation products of aldehydes, ketones, and b-diketones reacting with primary amines and related derivatives. These compounds are considered as an important class of ligands in coordination chemistry and have extensive applications in different fields [1]. Schiff bases de- rived from aldehydes and diamines constitute one of the most rel- evant synthetic ligand systems with importance in asymmetric catalysis and they have preferred stock in broad range of transi- tion-metal catalyzed reactions including lactide polymerization, epoxidation of olefins, hydroxylation, and asymmetric ring open- ing of epoxides [2–8]. Schiff bases containing amphiphiles in poly- meric films exhibit interesting optical and electronic properties [9,10]. They have other features, such as catalytic, antimicrobial, antifungal, antiviral applications, and also synergistic effect on insecticides, plant growth regulation, anti tumoring, and dying applications [11]. It is very well known that medium plays a dramatic role on the outcome of chemical reactions. Ionic liquids, as organic electrolytes and neoteric green solvents containing the bulky cations and an- ions, are used in many fields, such as catalysis, chemical reactions, separations, electrochemistry, and nanoscience applications [12]. Recently, a series works have been reported on the Schiff base and its metal complexes in the presence of some ionic liquids. A new cyanide optode was designed using Schiff base complex, [N,N 0 -bis(salicyliden)-2,3-diaminopyridine]tributylphosphine co- balt(III) percholorate monohydrate complex, which was coated on transparent triacetylcellulose film as membrane. The sensitivity of the method was improved by using ionic liquid, 1-butyl-3-meth- ylimidazolium hexafluorophosphate [BMIM][PF 6 ], introduced in constructing the optode membrane. The optode was successfully applied for the determination of cyanide in drinking water [13]. In a new method, Schiff base extracting agent (PMBP-2-ABT) was established for the extraction of heavy ions, by PMBP-2-ABT/ionic liquid binary-water phase system [14]. A series of square planar nickel (II) complexes containing N,O donor Schiff base ligand have catalytic activities for the oxidation of alcohols in ionic liquid media [15]. The asymmetric epoxidation of limonene has been performed using manganese (III) Schiff base complex dissolved in 1-n-butyl-3-methylimidazolium tetrafluoroborate ([BMIm]BF 4 ) io- nic liquid and hydrogen peroxide as oxidant. The manganese (III) chiral Schiff base complex in ionic liquid was found to be stable and efficient for the epoxidation of limonene with hydrogen perox- ide as oxidant [16]. Because of the importance and extensive applications of Schiff bases and ionic liquids as mentioned above, it is necessary to study the thermodynamic properties of Schiff base in the presence of 0021-9614/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jct.2013.04.022 ⇑ Corresponding author. Tel.: +98 411 3393139; fax: +98 411 3340191. E-mail addresses: hemayatt@yahoo.com, hemayatt@tabrizu.ac.ir (H. Shekaari). J. Chem. Thermodynamics 64 (2013) 58–64 Contents lists available at SciVerse ScienceDirect J. Chem. Thermodynamics journal homepage: www.elsevier.com/locate/jct