Authors: Özge BAĞLAYAN, Naki ÇOLAK, Yasemin SÜZEN and Mustafa ŞENYEL
Schiff bases have wide applications in chemosensor chemistry , biological and pharmacological processes , on the other hand they have photochromic and/or thermochromic properties  leading to its application in various areas such as the control and measurement of radiation intensity display systems and optical computers . In this study, a novel bidentate Schiff base derived from 2-amino-5,5,7,7-tetramethyl-4,5,6,7-tetrahydrobenzol[b]thiophene-3-carbonitrile (Fig. 1). It was investigated theoretically and experimentally. FT-IR and Raman spectra have been recorded in the region of 4000-400 cm-1 and 4000-200 cm-1, respectively. For theoretical calculations, crystal data of the molecule were used. The optimized geometrical parameters, normal mode frequencies and corresponding vibrational assignments of the compound have been examined by means of the density functional theory method, employing, the Becke-3-Lee–Yang–Parr functional and the 6-311++G(2d,2p) basis set. Furthermore, reliable vibrational assignments have been made on the basis of potential energy distribution (PED) and highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO) of the molecule have been predicted. Theoretical and experimental values were compared. All results indicate that B3LYP method is able to provide satisfactory results for predicting vibrational frequencies.
Keywords: Schiff bases, DFT, FT-IR, Raman