Synthesis, complex formation kinetics and thermodynamic study of some acyclic polyamine and N2O2 ligands with copper(II)

The polydentate ligands, 3-(2-aminocyclohexylamino)-2-(2-aminocyclohexyl aminomethyl) propionic acid (L1), 4,7,10-triazatridecanedinitrile trihydrochloride (L2), and 2,2'-(ethane-1,2-diyl) bis(methylazanediyl) diethanol (L3) were prepared and their structures investigated by FT-IR, NMR, and MS. The kinetics of complex formation between Cu(II) and L1, L2, and L3 were investigated in acidic aqueous solutions using the stopped-flow method. The stability constants of the complexes were determined by spectrophotometric titration (T = 293 K, = 0.1 mol L-1 NaClO4), using a diode array UV-Vis spectrophotometer equipped with peristaltic pump and pH meter. The stability constants for the complexes were CuL1 CuL2 CuL3. Activation enthalpies (H#) of these complexes were 55 kJ mol-1 for CuL1, 61 kJ mol-1 for CuL2, and 36 kJ mol-1 for CuL3, respectively.