Influence of the Nature of the Central Atom on the Basicity of Octa(3,5-di-tert-butylphenoxy)phthalocyanine Complexes

Knowledge of the parameters and mechanisms of proton transfer from the medium to the macrocyclic ligand in complexes of highly substituted phthalocyanines is necessary for optimization of technological processes of catalysis and design of functional materials. Octakis(3,5-di-tert-butylphenoxy)phthalocyanine complexes with 3d-metal ions have been synthesized, and their acid–base reactions have been studied by UV-vis and ¹H NMR spectroscopy. The chemical structure of the complexes has been determined using elemental analysis, MALDI-TOF mass spectrometry, IR, ¹H NMR, and UV-vis spectroscopy data. Complete protonation of the Co, Ni, and Cu complexes takes place in dichloromethane–trifluoroacetic acid mixtures. Doubly and quadruply protonated forms have been identified in UV-vis spectra. The concentration ranges of existence, UV-vis parameters, and the thermodynamic stability constants of the protonated forms, as well as their relationship with the electronic structure of the coordination center, have been determined.