Radia Mahboub, Samira Louhibi, Molecular and Semi-Empirical Mechanic Studies of Copper-Histamine Chloride Complex, Volume 64, International Letters of Chemistry, Physics and Astronomy (Volume 64) https://www.scipress.com/ILCPA.64.34 Abstract: In the present work, we describe and characterized the molecular structure and molecular orbital of Cu (His)Cl<sub>2 </sub>by two methods: molecular mechanic and semi-empirical PM3 simulations. First, we determine the geometry structural properties of the Cu (Hist)Cl<sub>2</sub> complex by molecular mechanic method. Then we compare the calculations method with the experimental data of Cu (His)Cl<sub>2</sub> crystal complex. We find that the optimized parameters obtained by MM method are in good agreement with those observed experimentally. After, we evaluate the quantum chemical parameters using PM3 simulations and we discuss the chemical reactivity of Cu (II) ion and the stability of Cu (His)Cl<sub>2 </sub>molecule. We obtain a large gap with PM3 method. We evaluate the electrophilicity index of the complex. We also calculate the deformation energy. We deduce from quantum calculations that Cu (Hist)Cl<sub>2 </sub>molecule has high chemical reactivity and is more stable. Finally, we calculate the relative and average errors to estimate the quality of each method. We show that average errors vary as follow: for bonds are 7.833 and 2.692 %, and for angles are 7.755 and 5.309 % using MM+ and PM3 respectively. We conclude that both molecular mechanic and semi-empirical calculations agree very well with the experimental data. Keywords: Copper Complex, Deformation Energy, Ectrophilicity Index, MM+ Method, PM3 Method