Complexation of Tetraphenyltetrabenzoporphine with Cu(II), Cd(II), Zn(II), and Co(II) Salts in Organic Solvents

The rate and activation parameters of tetraphenyltetrabenzoporphine (H₂TPTBP) complexation with 3d-metal acetates and acetylacetonates are shown to be determined by the solvent nature. With an increase in the electron-donor properties of a solvent, the reaction rate increases due to protonation of N–H bonds and decreases as MA _m (Solv) _{n – m} salt solvates become more stable. As the result, the rate of a reaction with ZnAc₂ increases in the series: DMF < dmso=">< py=">< proh-1="><>₃CN <>₆H₆. In inert and weakly coordinating solvents, the transition state of a reaction is supposed to be formed according to the mechanism of contraction of the salt coordination sphere. The rate of H₂TPTBP reaction with metal acetates in pyridine changes in the series: Cu(II) > Cd(II) > Zn(II) > Co(II), while the stability of the obtained complexes decreases in the series Cu(II) > Co(II) > Zn(II) > Cd(II). It is shown that the spectral criterion of the complex stability can be used in the series of metal complexes with one ligand, but it is violated if the ligand structure is changed.