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

摘要

The phthalocyaninato double- decker complexes [M(obPc)(2)](0) (M = Y-III, Tb-III, Dy-III; obPc = 2,3,9,10,16,17,23,24-octabutoxyphthalocyaninato), along with their reduced ([M(obPc)(2)](-)[P(Ph)(4)](+); M= Tb-III, Dy-III) and oxidized ([M(obPc)(2)](+)[SbCl6](-) (M= Y-III, Tb-III) counterparts were studied with H-1, C-13 and 2D NMR. From the NMR data of the neutral (i.e., with one unpaired electron in the ligands) and anionic Tb-III 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 H-1 and C-13 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)(2)](0) (M= Tb-III and Dy-III) at room temperature. From the NMR data of the cationic Tb-III 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-III double- decker complexes was also studied.