RuCl2(Azpy)2and RuCl2(Nazpy)2 are two bidentatesazopyridineruthénium(II) complexes that were characterized by DFT calculation. Azpy and Nazpy stand respectively for 2-phenylazopyridine and 2-phenylazonaphtol. Several levels of prediction were performed comprising the functional hybrid B3LYP with LANL2DZEffective Core Potential (ECP) basis set either in gas or in condensed phase. Actually, five isomers are by experiment obtainable since azopyridine ligands are not symmetrical. But the synthesis that gathers RuCl3,3H2O with a ligand produces only two isomers named g-Cl and d-Cl. Both isomers are C2 symmetrical and the most abundant is assumed to beg- Cl. The particularity ofd-Cl is that both chlorine atoms are different. Besides, while symmetry is through the bisector of Npy-Ru-Npy angle in g-Cl, it is however seen through the axis Cl-Ru-Cl in d-Cl. Moreover, the 1H NMR calculation shows up that LANL2DZ effective core potential basis set provides chemical shifts that match with experiment data and requires to be exploited in gas phase. Furthermore, frequency calculations at 298.15K show up that the most stable isomer is d-Cl. Nevertheless, when synthesis is performed at high temperature, the most profitable isomer becomes g-Cl.