Unexpected Supramolecular-Induced Redox Switching in Sandwich Gd Bisphthalocyaninate

The redox state of the phthalocyanine in sandwich lanthanide complexes is crucial for their applications. In this work, we demonstrate that the cation-induced supramolecular assembly of crown-substituted phthalocyanine lanthanide complexes Ln[(15C5)₄Pc]₂ can be used to control the redox state of the ligand simultaneously with the coordination sphere of the central metal. We achieve unprecedented redox switching of phthalocyanine ligands in a double-decker Gd(III) complex, resulting from the intramolecular inclusion of potassium cations between the decks with simultaneous twisting of the ligands (the skew angle between them decreases from 44.61 to 0.21°). Such a structural change leads to an increase in the deck-to-deck distance and drastically facilitates ligand reduction. This process was shown to be anion-dependent: only potassium salts of weak acids (KOPiv and KOAc) induce intramolecular inclusion of cations with redox switching in contrast to salts of strong acids (KBr, KOPic, KSCN, and KPF₆), where such a redox process does not occur. This breakthrough opens new avenues for controlling the electrochromic properties, of phthalocyanines, along with other properties, such as electrical conductivity, optics, etc.