On different solvate forms of octamethyltetraphenylporphin in organic solvents

It was found that octamethyl-meso-tetraphenylporphin (OMTPP) in different o rganic solvents features different electronic adsorption and fluorescence s pectra. Based on a consideration of the properties of the solvents and a co mparison of the absorption spectra obtained to those of known porphyrins in specific media, it was concluded that OMTPP exists in the following forms. In toluene and acetone solutions, OMTPP exists in the form of a free base. In acidic media, OMTPP forms disalts. In aqueous ethanol, a solvent molecu le is bound to the nitrogen atom. In dimethyl sulfoxide, piperidine, and di methylformamide solutions, a solvent molecule attaches itself to the hydrog en atom of an NH group and accepts this atom. In ethanol and methyl celloso lve solutions, two solvent molecules attach themselves to central protons o f OMTPP and, probably, detach these atoms from the porphyrin. The fact that OMTPP specifically interacts with the solvents was explained by its enhanc ed acidity and basicity tin comparison with simpler porphyrins), which are caused by a decrease in the degree of screening of the central part of the molecule by its pi -electron system due to the nonplanar structure of the O MTPP molecule.