Acid-base interaction of octaaryltetraazaporphyrin complexes in a proton-donor medium

Abstract

The processes of acid-base interactions of the octaaryltetraazaporphyrin complexes in a protondonor environment based on acetic or trifluoroacetic acids was studied. The constants of the acidity of the protonated forms were determined. The introduction of electron-withdrawing functional groups was shown to reduce the basicity of the meso-nitrogen atoms of the macrocycle. The decrease in the cobalt oxidation state was shown to reduce the complex basicity.Porphyrazines are weak multi-center bases. In the case of porphyrazine metallocomplexes the acid-base interactions occur with the involvement of exocyclic (meso) nitrogen atoms. The process of acid-base interactions of porphyrazines is rather complicated [1-3]. The resulting acid forms differ from each other by the degree of the proton transfer from the acid molecule to the donor center. The number of the porphyrazine donor centers involved in the acid-base interaction and the constants of acidity of the produced acid forms depend on the structure and properties of the protondonor environment of the porphyrazine. To date a large experimental material was accumulated and summarized on the study the reaction of the porphyrazines acid-base interactions [1,2].In this paper we first investigated the effect of the structure of octaaryltetraazaporphyrin complexes, oxidation state of the metal, and nature of the proton environment on the reactions of acid-base interaction of the complexes.Interaction of a porphyrazine with an acid results in characteristic changes in the electron absorption spectra that register formation of various acid forms.