Equilibria of Cu(II) with newly synthetised ligands H4L1 and H4L2 were investigated by the glass electrode potentiometry at 25 degrees of Celsius and I = 0.1 M KNO3. A simple chemical model with metal:ligand molar ratio 1:1 was found in the systems. Presence of main species , CuL1 (log Beta = 20.37(4)) and CuL2 (log Beta = 17.19(2)) was also confirmed by MALDI-TOF/MS. The dissociation kinetics of the complexes was followed by spectrophotometry and mechanism of the dissociation was proposed. Activation parameters (activation enthalpy and entropy) of the dissociation were estimated. For Cu(II)-H4L1 system, the complex dissociation starts after protonization of phosphinic pendant arms and its mechasnism is similar to the decomplexation of [Cu(cyclen)]2+. The complex with H4L2 is kinetically much less stable and the proton transfer from phosphinic pendant arm to the azacycle plays a significant role in the reaction mechanism.