Terbium(III) Phthalocyaninato Multiple-Decker Complexes in High Oxidation States: Correlation Between Electronic, Structural and Magnetic Properties and Unexpected Triplet Biradical States

Herein we present a comprehensive study of the highly oxidized species of multiple-decker complexes composed of Tb(III) and Cd(II) ions and two to five phthalocyaninato ligands, which are stabilized by electron-donating n-butoxy chains. Paramagnetic ¹H NMR measurements for the series of triple, quadruple and quintuple-decker complexes revealed that ligand oxidations lead to a decrease in magnetic anisotropy, as predicted from ab initio calculations. Unusual paramagnetic shifts were observed in +2e charged quadruple and quintuple-decker complexes, indicating that those two species are actually triplet biradicals. The X-ray structural analysis for the series of oxidized multiple-decker complexes revealed that all the species show an axial compression induced by the ligand oxidations, resulting in the bowl-shaped distortion of the ligands, in agreement with predictions from DFT calculations. Magnetic measurements revealed that the series of complexes show single-molecule magnet (SMM) properties, which are controlled by the multi-step redox induced structural changes.