Unexpected Supramolecular Induced Redox Switching in Sandwich Gd Bisphthalocyaninate

Abstract

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. It was demonstated that this process is anion dependent. Thus, only potassium salts of weak acids (KOPiv, 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.

Unexpected Supramolecular-Induced Redox Switching in Sandwich Gd Bisphthalocyaninate

“…Here, we report comprehensive solution and single-crystal X-ray diffraction characterization of the product of intramolecular potassium ion inclusion in the double-decker gadolinium complex Gd­[(15C5) 4 Pc] 2. This is the first direct structural characterization of the alkali cation intercalation into double-decker lanthanide complexes with crown phthalocyanines. We demonstrate that for the middle lanthanide double-deckers, supramolecular interactions can additionally control the redox state of the ligand, which is crucial for electron conductivity …”