Complexes were synthesized from aspirinate of Cu(II) and acetate of Cu(II) dihydrated with the ligand 1,3-thiazole and were characterized through elemental analysis, magnetic moment, FT-IR spectroscopy, and thermogravimetric analysis. Moreover, semiempirical structural PM6 of both compounds were carried out. Ligand 1,3-thiazole coordinates with the Cu(II)ions through the nitrogen without break the dimeric unit Cu-2(RCOO)(4). To coordinate with the aspirinate of Cu(II), the ligand must to break tridimensional arrangement and to coordinate with the acetate of Cu(II)dihydrated, it replaced the water molecules. In both compounds, Cu-2(asp)(4)(Tz)(2) and Cu-2(acetate)(4)(Tz)(2), the PM6 calculations corresponding to the Cu-Cu distances in the dimeric unit Cu-2 (RCOO)(4) presents a small difference 0.03A(c), but the magnetic moments are very different. The complex with aspirinate presents a magnetic moment of 1.79 M.B and that with acetate is 1.4 MB.