حسابات ميكانيك الكم لبعض مركبات الهيدرازون

Quantum mechanical calculations of some hydrazones

Quantum mechanical calculations by the one of semiempirical method MINDO/3-FORCES were applied, It also was held calculations according to the Density Functional Theory (DFT) with hybrid function B3LYP and 6-311G , CEP-121G basis set by use Gaussian09 program for the purpose of comparison , and because of the great importance and extensively for Schiff bases that medical and industrial uses , has studied five Hydrazones derivative from benzoic acid hydrazide .
The equilibrium geometries (lengths of bonds and angles), charge , electron densities ،heats of formation ، dipole moments , energies of HOMO and LUMO orbital , energy gab ،ionization potential ، electron affinity , electronegativity , chemical hardness , electrophilicity , standard thermodynamics functions (U⁰ , H⁰ , S⁰ , G⁰ and A⁰) and fundamental vibration frequencies with corresponding IR absorption intensities were
calculated. The assignment for each one of the fundamental frequencies were also estimated.
The results were compared with experimental bond length values which measured by X-Ray diffraction and on the other hand to infrared vibrational spectra , identified Density Functional Theory was found nearest from experimental values compared with MINDO/3-FORCES model, because of
semiempirical method nature for it. And generally for all molecules is calculations appeared the following results :
Increasing in bond length which lie in the position that substituted with group, and decreasing at bond length at adjacent bonds and versa with substituted by donating groups , showed of decreasing in bond length which lies on substituted position and increasing of bond length at adjacent bonds .
We also showed the bond angles on the aromatic rings affected by withdrawal substitute, since increase in its value than analogous which substituted with donating group , while with the adjacent angles, we show the decreasing in its values , at substituted with donating substituent and increase in case of substitute withdrawal group .
The electronic density increased at nitrogen atom to azomethine group , in compounds substituted with electron donating groups while the corresponding compound which substituted with electron with withdrawing groups in the aromatic ring .
The values of the dipole moment , ionization potential , electron affinity , electronegativity and electrophilicity in op compound which substituted with electron withdrawal nitro group (-NO2) higher than with substituted by donating groups This is the opposite to the results the standard thermodynamics functions (U⁰ , H⁰ , S⁰ , G⁰ and A⁰) , gives great results for compounds substitutes with electron donating groups the compounds in comparison with the compound substituted with electron withdrawing groups. The chemical hardness is complement with energy gab : benzoic hydrazide has highest value more stable , while in compound substituted dimethyl amino group it large sized has a lowest value of hardness less stable .