Solvatochromism of the Free Base Corroles

Abstract

For two free base corroles with different architecture of peripheral substitution, the solvatochromic shifts of absorption bands in a series of solvents of different nature are herein determined, and the nature of the solvatochromic effects is analyzed by the Valentine method. It is found that the solvatochromism of the free bases of corroles originates due to universal nonspecific interactions, and the short-wavelength T2 tautomer experiences stronger solvation. It is shown that in polar aprotic solvents (acetone, acetonitrile, dimethylformamide,
 and dimethylsulfoxide), specific acid-base interactions occur simultaneously, leading to the formation of the deprotonated form. It is found that both deprotonated and protonated forms of corroles also show nonspecific solvation, leading to solvatochromic shifts, the magnitude of which exceeds that for free base corroles. It is proposed that this feature is due to an excess (negative or positive) electronic charge of the macrocycle.