In this work, the synthesis, structure, quantum chemical analysis, and spectroscopic properties of complex compounds [Co(C7H5O3)2(L1,2,3)2] (where L1-nicotinamide, L2-thiocarbamide, L3-acetamide) obtained on the basis of the divalent cobalt (Co(II)) ion with amide derivatives were studied. Mhydroxobenzoic acid (mgb) was used as the initial ligand. Quantum-chemical calculations of the complex compounds were analyzed, IR spectra were compared, and changes in the vibration frequencies of the ligands' functional groups were recorded.