Ligand π‐Radical Interaction with f‐Shell Unpaired Electrons in Phthalocyaninato–Lanthanoid Single‐Molecule Magnets: A Solution NMR Spectroscopic and DFT Study

<jats:title>Abstract</jats:title><jats:p>The phthalocyaninato double‐decker complexes [M(obPc)<jats:sub>2</jats:sub>]<jats:sup>0</jats:sup> (M= Y<jats:sup>III</jats:sup>, Tb<jats:sup>III</jats:sup>, Dy<jats:sup>III</jats:sup>; obPc=2,3,9,10,16,17,23,24‐octabutoxyphthalocyaninato), along with their reduced ([M(obPc)<jats:sub>2</jats:sub>]<jats:sup>−</jats:sup>[P(Ph)<jats:sub>4</jats:sub>]<jats:sup>+</jats:sup>; M=Tb<jats:sup>III</jats:sup>, Dy<jats:sup>III</jats:sup>) and oxidized ([M(obPc)<jats:sub>2</jats:sub>]<jats:sup>+</jats:sup>[SbCl<jats:sub>6</jats:sub>]<jats:sup>−</jats:sup> (M=Y<jats:sup>III</jats:sup>, Tb<jats:sup>III</jats:sup>) counterparts were studied with <jats:sup>1</jats:sup>H, <jats:sup>13</jats:sup>C and 2D NMR. From the NMR data of the neutral (i.e., with one unpaired electron in the ligands) and anionic Tb<jats:sup>III</jats:sup> complexes, along with the use of dispersion corrected DFT methods, it was possible to separate the metal‐centered and ligand‐centered contributions to the hyperfine NMR shift. These contributions to the <jats:sup>1</jats:sup>H and <jats:sup>13</jats:sup>C hyperfine NMR shifts were further analyzed in terms of pseudocontact and Fermi contact shifts. Furthermore, from a combination of NMR data and DFT calculations, we have determined the spin multiplicity of the neutral complexes [M(obPc)<jats:sub>2</jats:sub>]<jats:sup>0</jats:sup> (M=Tb<jats:sup>III</jats:sup> and Dy<jats:sup>III</jats:sup>) at room temperature. From the NMR data of the cationic Tb<jats:sup>III</jats:sup> complex, for which actually no experimental structure determination is available, we have analyzed the structural changes induced by oxidation from its neutral/anionic species and shown that the interligand distance decreases upon oxidation. The fast electron exchange process between the neutral and anionic Tb<jats:sup>III</jats:sup> double‐decker complexes was also studied.</jats:p>