Chemical interaction "porphyrin-solvent" between the reaction center of basic solvent and weakly acidic macrocyclic NH group is analyzed for different types of porphyrin ligands (H 2 P). Planar and distorted ligands, common H 2 P and porphyrin analogs are considered using spectrophotometric titration, kinetic measurements, 1 H NMR and fluorescent spectroscopy as well as quantum-chemical calculations. Reaction is usually reversible for non-planar compounds and proceeds in kinetic regime in the case of H 2 P with more rigid aromatic structure like porphyrazines. Deepening of the saddle non-planar conformation favors formation of H-associates as compared to other distorted types of porphyrins (ruffle, wave, stepped, etc.) due to polarization of saddle structure. In dependence on the class of H 2 P analogs they either, like corroles, repeat behavior of saddle non-planar common porphyrins, or undergo some kind of specific transformations like tautomerism of inverted H 2 P analogs. Addition of a stronger base like diethylamine or piperidine to solution of H-associate in polar donating solvent usually results in formation of porphyrin monoanion.
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