Introduction of various organic molecules as additional ligands into metal complexes can substantially improve their properties, because the resulting complexes can be more effective. As result of interaction of structural block [Co(N3)(DmgH)2(Н2О)] with sulfanilamide derivative the mononuclear molecular complex [Co(N3)(DmgH)2Sda] (1) was obtained, where DmgH- = dimethylglyoximate monoanion, Sda = sulfanilamide derivative with substituted radical R (NH2– C6H4–SO2–NH–R)). In order to substitute SAM (sulfanilamide derivatives) from the complexes [Co(N3)(DmgH)2SAM] they were treated with a series ligands: pyridine (Py), nicotinamide (Nia), isonicotinamide (INia), thiouree (Thio), triphenylphosphine (PPh3), isonicotinic acid (HINia), 4pyridinealdoxime (4-paoH), 4,4′-bipyridine (bpy) and NH4NCS. Eight mononuclear molecular complexes [Со(N3)(DmgH)2(Py)] (2), [Со(N3)(DmgH)2(PPh3)] (3), [Со(N3)(DmgH)2(Thio)] (4), [Со(N3)(DmgH)2(Nia)] (5), [Со(N3)(DmgH)2(INia)] (6), [Со(N3)(DmgH)2(HINia)]·H2O (7), [Со(N3)(DmgH)2(4-paoH)]·DMF (8), [Со(N3)(DmgH)2(bpy)] (9), and two binuclear [(Со(N3)(DmgH)2)2bpy]·0.5H2O (10), [(Со(N3)(DmgH)2)2bpy]·H2O (11) polymorphs were prepared and characterized by X-ray diffraction on single crystal (Fig. 1), elemental analysis and IR spectroscopy. Compound NH4[Co(SCN)2(DH)2]·3H2O (12) represent the single ionic complex, which was obtained as result of substitution of both, SAM and N3 - units by SCN-.figureFig. 1. X-ray molecular structure of complexes 1 (a), 6 (b), 10 (c), and 12 (d) Molecular geometries, electronic structure and the substitution reaction energies were calculated for all the considered compounds by the DFT B3LYP method with the 6-31G basis sets. Calculations proved that preparation of new complexes by substitutions of the ligands is an energetically favorable processes.