Multiwavelength spectrophotometric-thermodynamic studies of complexation reactions of newly synthesized triazenes with Hg2+, Pb2+, Zn2+, and Cd2+ in MeOH, EtOH, DMF, and DMSO

The complexation reaction of Hg2+, Pb2+, Zn2+, and Cd2+ cations with four newly synthesized triazene ligands was studied spectrophotometrically in nonaqueous solvents (MeOH, EtOH, DMF, and DMSO) at various temperatures. Stability constants (K1 and K2) and stoichiometries of formed adducts (1:1 and 1:2 ligand to metal ion) were calculated by computer refinement of experimental spectral mole ratio data by SQUAD program. The results indicated that the donor number, dielectric constant, the acceptor number of the solvents play an important role in the complex stability. Besides, the shape and size of the solvent molecules were significant factors in the studied reactions. Between log 01 and log 02, a linear relationship was illustrated for most of the complexes under different conditions. The Van't Hoff equation was used to calculate AG degrees, AS degrees, and AH degrees from the dependence of formation constants on temperature. After calculating thermodynamic data at different temperatures, a good linear correlation was obtained from the TAS degrees - AH degrees plot resulting in the entropy-enthalpy compensation for complexation reactions. (c) 2022 Elsevier B.V. All rights reserved.

Automated summary

The complexation reactions of Hg2+, Pb2+, Zn2+, and Cd2+ cations with newly synthesized triazene ligands were studied in nonaqueous solvents. The results showed that the properties of the solvents and the shape of solvent molecules played important roles in the complex stability. Furthermore, a linear relationship between the formation constants and temperature was observed, and entropy-enthalpy compensation was found in the complexation reactions.