Abstract: The complexes of (Z)-10-(2-(4-amino-5-thioxo-4,5-dihydro-1Н-1,2,4-triazol-3-yl)hydrazono)-9-phenanthrone (HL) with the Co(II), Ni(II), and Cu(II) salts, [CoLAcDMF] (I), [NiLAcDMF] (II), [CuL(Н 2 О)]ClO 4 (III), and [CuLAc] (IV), are synthesized and studied. The titration of a solution of HL in DMF with aqueous solutions of CoAc 2 , NiAc 2 , Cu(ClO 4 ) 2 , CuAc 2 , Cd(NO 3 ) 2 , or ZnSO 4 leads to the bathochromic shift of the long-wavelength absorption band by 35–77 nm in the UV spectra. The formation constants and compositions of the complexes in solutions are determined from the results of titration. The structures of complexes I–IV are proposed on the basis of the DFT calculations and spectral data: the ligand being in the deprotonated form of the thione tautomer is coordinated by the metal cations through the oxygen atom of the carbonyl group and the nitrogen atoms of the hydrazo and amino groups to form two metallocycles, six- and five-membered (6 + 5). The coordination mode is completed by the acetate ion and DMF molecule (in I and II), acetate ion (in IV), or Н 2 О molecule (in III). © 2019, Pleiades Publishing, Ltd.