Thioamide group is an important part of a large number of drug structures, yet there is no exact description of its infrared spectra and coordination behaviour. Three compounds i.e. dithiooxamide (DTO), n-propyl (PDTO) and Schiff base (SDTO) derivatives of DTO were chosen for the present experimental work and theoretical treatment, in addition to copper (II) complexes of DTO and SDTO. The reaction of DTO with both n-propyl chloride and p-nitrobenzaldehyde gave the two new derivatives, PDTO and SDTO, respectively. The reaction of copper (II) chloride with both DTO and-SDTO gave the die-nuclear octahedral, Cu2 (DTO)(C1)4(H2O)4 complex, and mono-nuclear octahedral [Cu2(SDTO)2(H2O)2]Cl2 complex, respectively. All the prepared compounds were isolated and characterized by their melting points , vibrational and electronic spectra , metal analysis , thermal analysis and magnetic measurements. The alb initio method at high level was used for calculating the relative energies and infrared,, spectra of the three prepared compounds (DTO, PDTO and SDTO), the ab initio calculations indicating the tautomeric structure of DTO , and help to predict the most stable structure among the four probable structures [trans-DTO/A] . For PDTO and SDTO , the cis isomers were more stable than the trans ismers . The semi-empirical AMI method was used in calculating the electrostatic potential and HOMO-LUMO of the reactant molecules, thereby the reactive, sites were characterized . The calculations predict the reaction sites in the preparation of PDTO and SDTO and its copper (II) complex through their frontier orbitals . The semi-empirical PM3 method was used for the calculation of binding energies for the probable geometries of copper (II) complexes with DTO and SDTO . The total relative binding energies (Δ Eb) of DTO-Cu(l:2) complexes showed that the [†DTO/I-Cu(trans)] was the most stable, also the total relative binding energies of DTO-Cu(2:1) complexes showed that the imine conformation [2DTO/I-Cu(trans)J was more stable than the amine conformation . The PM3 calculation of SDTO-Cu(l:2) complexes showed the [††SDTO-Cu] was the most stable, while the SDTO-Cu (2:1) complexes showed the trans isomer [2SDTO (trans) - Cu (trans)] was more stable than the cis isomer.