ИСТИНА

N-heterocyclic reagents find their application as luminescent materials and extractants for the separation of f-elements. To study the intramolecular processes occurring in complexation reactions, we need to study the thermodynamic parameters of them. One of the most important thermodynamic parameters is the stability constant of complexes. The stability constant of complexes is a general characteristic of the behavior of the ligand during complexation. In this work, we study the stability constants of complexes of f-elements with two types of ligands: the substituted diamides of heterocyclic carboxylic acids and N-heterocyclic phosphine oxides. The stability constant of complexes was measured by spectrophotometric, luminescent and calorimetric titrations. The equilibrium system was studied in acetonitrile and ethanol with various water contents. The composition of complexes was determined by the Job plot and by the titrimetric methods. The number of complex species in the equilibrium system and their composition were analyzed by matrix analysis. The stability constants of complexes (logβ1) were calculated using the HypSpec2014 program. Authors thank the RSF (project No. 16-13-10451‬) for financial support.