Spectrochimica Acta Part A 79 (2011) 1573–1583 Contents lists available at ScienceDirect Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy j ourna l ho me page: www.elsevier.com/locate/saa Synthesis, characterization, tautomerism and theoretical study of some new Schiff base derivatives Güls ¸ en Türko˘ glu a , Halil Berber a,∗ , Hakan Dal a , Cemil Ö˘ gretir b a Anadolu University, Faculty of Science, Chemistry Department, 26470 Eskis ¸ ehir, Turkey b Eskis ¸ ehir Osmangazi University, Faculty Arts and Sciences, Chemistry Department, 26040 Eskis ¸ ehir, Turkey a r t i c l e i n f o Article history: Received 25 February 2011 Received in revised form 30 March 2011 Accepted 10 April 2011 This paper is dedicated to Dear Professor Cemil Ö˘ gretir. Keywords: Schiff basel Synthesis Characterization Tautomerism Theoretical calculation PM6 method a b s t r a c t New Schiff base derivatives were prepared by the condensation of 5-chloro and 5-bromo salicylaldehyde with bis(o-aminophenol)ethers. Five bis(o-nitrophenol)ether compounds were synthesized using some ditosylate, 1,3-dibromopropane and 1,4-dibromobuthane with o-nitrophenol. These compounds were reduced to bis(o-aminophenol)ethers. The products have been characterized by elemental analysis, FTIR, 1 H, 13 C NMR, HETCOR and HMBC spectroscopic techniques. The tautomerisms of all of the Schiff bases compounds were determined in DMSO, CHCl 3 , C 2 H 5 OH and C 6 H 12 solvents and in both acidic and basic media using the UV–vis spectrophotometric method. The heat of formation (H f ), enthalpy (H), entropy (S), Gibbs free energy (G f and G), stable isomers, conformations and tautomers of the synthesized compounds are calculated using the MOPAC2009 (PM6) program. © 2011 Elsevier B.V. All rights reserved. 1. Introduction The development of the so-called Schiff base compounds has attracted a lot of interest in the fields of coordination chem- istry and material sciences [1,2]. Schiff bases that have a solvent dependent UV–vis spectrum (solvatochromicity) can be suit- able NLO (non linear optical active) materials [3]. The Schiff base can accommodate different metal centers involving vari- ous coordination modes thereby allowing successful synthesis of homo and hetero metallic complexes with varied stereochemistry [4]. Schiff bases are important in diverse field chemistry owing to their biological activity [5]. Apart from the biological activity, pho- tochromism is another characteristic of these materials leading to its application in various areas, such as the control and measure- ment of radiation intensity, display systems and optical computers [6]. Some crown ether-containing ortho hydroxylated Schiff bases have been synthesized and their complexation properties with transition metal cations have been investigated [7–9]. The Schiff base ligands are one of the most widely used ligands due to ∗ Corresponding author: Tel.: +90 222 335 05 80x4827; fax: +90 222 320 49 10. E-mail address: hlberber@anadolu.edu.tr (H. Berber). the ease of formation and remarkable versatility, and therefore they have played an important role in the development of coor- dination chemistry as they readily form stable complexes with most of the transition metals [10]. Symmetrical diimines and their metal complexes have been used as models for biological systems for their antimicrobial and anticancer activities [11,12]. They have also been used in the catalytic reactions [13] and oxidation reactions [14,15]. Additionally, they have material prop- erties and analytical applications such as ion selective electrodes [16]. The proton transfer equilibrium in 2-hydroxy Schiff bases in solution and solid state has been investigated using mass spec- tra [17], NMR [18–22], UV–vis [23–27] and X-ray crystallography [28–30]. Schiff bases with OH group in ortho position to the amino group are of interest mainly due to the existence of either O–H . . .. . . N or O . . ... N–H type of hydrogen bond and tautomerism between enol-imine and keto–amine form. In these compounds, short hydrogen bonds between the OH group in ortho position to the imino group and the imine nitrogen are due to stereochem- istry. In this study, we synthesized new Schiff bases (Fig. 1) and investigated using elemental analysis, FTIR, 1 H, 13 C NMR, HET- COR and HMBC spectroscopic techniques [31]. Then the tautomers of all of the Schiff bases compounds were determined using the UV–vis spectrophotometric method. Conformations and tautomers 1386-1425/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.saa.2011.04.089