الفهرس 
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Abstract
In this thesis the electronic structure and spectra of some Schiff base derivative compounds are investigated using TD-DFT/B3LYB/6-311G (d, p) level of theory. The results of calculations show that all the studied compounds 1–4 are non-planar, as indicated from the dihedral angles. Four Schiff bases were used they are: 4-(2-(4-nitrophenyl)ethylidene)aminohippurate, 4-(2-(N,N-dimethylephenyl)ethylidene)aminohippurate, 4-(2-(4-chlorophenyl)ethylidene)aminohippurate, 4-(2-(3-hydroxy-4-methoxyphenyl)ethylidene)aminohippurate. The natural bond orbital (NBO) analysis were discussed in terms of the extent of delocalization, intermolecular charge transfer and second order perturbation interactions between donor and acceptor MOs. The calculated EHOMO and ELUMO energies of the studied compounds can be used to explain the extent of charge transfer in the molecule and to calculate the global properties; the chemical hardness (η), global softness (S), electrophilicity (ω), and electronegativity (χ). The calculated nonlinear optical parameters (NLO); polarizibilty (α), anisotropy of the polarizibility (Δα) and first order hyperpolarizibility (β) of the studied compounds have been calculated at the same level of theory and compared with the proto type Para-Nitro-Aniline (PNA), show promising optical properties. 3D-plots of the molecular electrostatic potential (MEP) for some of the studied compounds are investigated and analyzed showing the distribution of electronic density of orbital’s describing the electrophilic and nucleophilic sites of the selected molecules. The electronic absorption spectra of the studied compounds are recorded in the UV-VIS region, expermintally in both ethanol (as polar solvent) and dioxane (as non-polar solvent), and theoretically in gas phase, dioxane and ethanol at CAM-B3LYP/6-311G (d, p). Electronic configurations contributing to each excited state are identified and the relevant MOs are characterized. The band maxima (λmax) and intensities of the spectra are found to have solvent dependence. The bands of compounds 1, 2, and 4 show blue shift, while compounds 3 show red shift. The thermal and thermochemical calculations theoretically on the use of Gaussian 09 were performed. The equations used for calculation of entropy, energy, translational, electronic, rotational and vibrational were applied for theoretical study to understand the solvent effect and structure properties of the solid material used . the starting point in each case is the partition functions Q (V, T) for the compounds used. All the statistical thermodynamic parameters for the chosen four Schiff Base compounds were calculated like, different partition functions , dipole moments, quardrupole moments , sum of electronic and zero point energy, sum of electronic and thermal energies, sum of electronic and thermal enthalpies, sum of electronic and thermal free energies. Also translational, rotational, vibrational, heat capacity at constant volume and entropies for the four Schiff Base compounds in gas, dioxane and ethanol media were calculated theoretically and their values are clear in the thesis. All the compounds have dipole moments and they are great for compound 2 followed by 1 with the tendency : 2 > 1> 3 > 4, Indicating the greater activity for compound 2 with the ionic species and less reactivity with neutral compounds and natural agents .Opposite trend can be expected for compound 4.The vibrational entropy is greatest for compound number 4 giving trend : 4 >1>3 >2 Indicate more activity due to vibration energy for compound number 4. Rotational energies for all the four compounds are approximately the same. The thermal vibration energy are great for compound number 2 followed by compound 4 with trend : 2 > 4 > 1 > 3 Indicating greater activity for interaction with salts ,compounds neutral and organic compounds for compounds 2 and 4.All the evaluated statistical thermodynamic data indicate the more activity for compound 4 with neutral compounds and natural materials and compound 2 with ionic materials and salts. The biological activity of the studied compounds was tested against gram positive, gram negative and Fungi. A correlation between energetic, global properties and biological activity were investigated and discussed. The biological activity of the studied compounds show that compound 4 is the most active one ,whereas, the molecule 3 is the least active and the order of reactivity is : 4 > 2 > 1 > 3.