Analyse par diffraction X et calcul théorique des propriétés structurales des composés organiques à transfert de charges

Abstract

Our work is devoted to a comparative study between X-ray experimental and theoretical ab-initio structural analysis of the (2Z, 5Z) -3- N (4- methoxy phenyl) -2- N’ (4- methoxy phenyl imino) -5- ((E) -3-(2-nitrophenyl) allylidene) thiazolidin-4-one (MNTZ) molecule. The investigated compound has been synthesized by the reaction of thiazolidinones and appropriate aldehydes under basic conditions in ethanol solvent. Its crystal structure has been determined by X-ray diffraction analysis. The structural experimental investigation was completed by a theoretical investigation performed using the Density Functional Theory with B3LYP and GGA-PBE functionals at 6-31G(d, p) basis set. The DFT method with the two used functionals for the theoretical calculations gives results with good agreement to the experimental ones. Furthermore, Molecular properties of MNTZ molecule are performed by a combination of spectroscopic characterization (FT-IR, 1H and 13C NMR chemical shifts) and theoretical calculations. Vibrational wavenumbers , gauge independent atomic orbital (GIAO) 1H and 13C chemical shift values are investigated by using B3LYP and PBE functionals with the 6-31G(d,p) basis set in the ground state and compared with the experimental values. Each vibrational frequency is assigned on the basis of potential energy distribution (PED). The electronic transitions are calculated by time-dependent density functional theory (TDDFT). The energy band gap between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies are obtained by computing the frontier molecular orbitals using the B3LYP/6-31G(d,p) and PBE/6-31G(d,p) levels. The calculated HOMO and LUMO energies and NBO analysis revealed that charge transfer occurs within the molecule. Mulliken atomic charges and molecular electrostatic potential (MEP) are simulated using both functionals to find more reactive sites for electrophilic and nucleophilic attack. Finally, the thermodynamic functions (heat capacity, entropy and enthalpy) from spectroscopic data are obtained and discussed in the range of 100–1000 K.