30 卷 1 期 结 构 化 学˄JIEGOU HUAXUE˅ Vol.30, No. 1 2011. 1 Chinese J. Struct. Chem. 111~119 (E)-1-[4-(2-hydroxy-5-methoxybenzylideneamino)- phenyl]ethanone and (E)-1-[4-(2-hydroxy-4- methoxybenzylideneamino)phenyl]ethanone: X-ray and DFT-calculated structures ķ ŞAHİN Onur aĸ BÜYÜKGÜNGÖR Orhan a ALBAYRAK Çiğdem b ODABAŞOĞLU Mustafa c a (Department of Physics, Faculty of Arts and Sciences, Ondokuz Mayıs University, Kurupelit 55139 Samsun, Turkey) b (Department of Science Education, Sinop University, 57000 Sinop, Turkey) c (Chemistry Programme, Pamukkale University 20159 Denizli, Turkey) ABSTRACT The isomeric structures of (E)-1-[4-(2-hydroxy-5-methoxybenzylideneamino)- phenyl] ethanone (I) and (E)-1-[4-(2-hydroxy-4-methoxybenzylideneamino)phenyl]ethanone (II), both C 16 H 15 NO 3 , have been determined using X-ray diffraction techniques and characterized by IR, and their molecular structures have also been optimized at the B3LYP/6-31G(d,p) level using density functional theory (DFT). The energetic behaviors of the title compounds in solvent media have been examined using B3LYP method with the 6-31G(d,p) basis set by applying the polarizable continuum model (PCM). The total energies of the title compounds decrease with the increasing polarity of the solvent. In addition, DFT calculations of the title compounds’ molecular electrostatic potentials (MEP) were performed at the B3LYP/6-31G(d,p) level of theory. X-ray study shows that the title compounds both have strong intramolecular O–H···N hydrogen bonds. The molecules of I are linked into a one-dimensional framework structure by C–H···π interactions, while in II, intermolecular π···π interactions result in the formation of infinite chains running along the [010]. Keywords: crystal structure, Schiff base, DFT, molecular electrostatic potential 1 INTRODUCTION Schiff base compounds possess antifungal, antican- cer, anticonvulsant, diuretic and cytotoxic activi- ties [1～3] . Among them, o-hydroxy Schiff base ligands and their complexes derived from the reaction of o-hydroxyaldehyde with aniline have been extensi- vely studied [4, 5] and a number of these compounds have been used as models for biological systems [6] . They also have applications in organic synthesis, catalysis, biotechnology, and analytical chemistry [7～9] . Aromatic imines and their derivatives have been used successfully to study the resonance-assisted hydrogen bonds [10] . Tautomerism and isomerism phenomena for these compounds are of particular chemical and theoretical interest in the context of their photochromic and thermochromic properties [11] . o-Hydroxy Schiff bases exist as enol [12, 13] or keto [14] , Received 25 March 2010; accepted 20 September (CCDC 743178 and 768262) ķ The authors acknowledge the Faculty of Arts and Sciences, Ondokuz Mayıs University, Turkey, for the use of the Stoe IPDSII diffractometer (purchased under grant No. F279 of the University Research Fund) ĸ Corresponding author. E-mail: onurs@omu.edu.tr