Том 56, № 3 UDC 541.65:548.737 SUBSTITUENT EFFECTS ON THE ABSORPTION AND VIBRATIONAL SPECTRA OF SOME 2-HYDROXY SCHIFF BASES: DFT/TDDFT, NATURAL BOND ORBITAL AND EXPERIMENTAL STUDY S.A. Elroby1,3, S. Aboud1, S.G. Aziz1, R. Hilal1,2 1Chemistry Department, Faculty of Science, King abdullaziz University, Jeddah, Saudi Arabia 2 E-mail: rhilal@kau.edu.sa 3Chemistry Department, Faculty of Science, Cairo University, Giza, Egypt Chemistry Department, Faculty of Science, Benisuef University, Benisuef, Egypt Received March, 5, 2014 The electronic structure of salicylideneaniline (SA) and some of its derivatives are investigated both experimentally and theoretically. <...> The equilibrium geometric structures of the studied compounds are determined at the B3LYP/6-311++G** level of theory. <...> A set of 12 substituted SA derivatives is considered in the present work. <...> The choice of these substituents aims to create a push-pull system on the SA basic structure which would shade light onto its photo physics. <...> Assignments of the observed electronic transitions are facilitated via timedependent density functional theory (TDDFT) computations at the same level of theory. <...> The extent of delocalization and intramolecular charge transfer are estimated and discussed in terms of natural bond orbitals (NBO) analysis and second order perturbation interactions between donor and acceptor MOs. <...> Solvent effects on the electronic absorption spectra are discussed in terms of the difference in polarizabilities of the ground and excited states. <...> IR marker bands″ that characterize the SA framework are identified. <...> DOI: 10.15372/JSC20150303 Keywords: electronic spectra, vibrational spectra, DFT/TDDFT, solvent and substituent effects, NBO analysis, 2-hydroxy Schiff bases. <...> INTRODUCTION Aromatic Schiff bases have been [ 1—4] and still are the subject of numerous studies because of possible applications, e.g. in molecular memories and switches [ 5—7]. <...> This class of molecular systems is of fundamental interest because it shows two interesting phenomena, namely, the excited state intramolecular proton transfer (ESIPT) and photochromism. <...> The best known photochromic Schiff base is salicylideneaniline (SA). <...> In SA and its derivatives, the intramolecular hydrogen bonding opens a possibility of fast proton transfer between different tautomers followed by isomerization changes, leading to a metastable photochromic modification <...>