Ligand π-radical interaction with f-shell unpaired electrons in phthalocyaninato-lanthanoid single-molecule magnets: a solution NMR spectroscopic and DFT study

Marko Damjanović; Takaumi Morita; Keiichi Katoh; Masahiro Yamashita; Markus Enders

doi:10.1002/chem.201501944

Ligand π-radical interaction with f-shell unpaired electrons in phthalocyaninato-lanthanoid single-molecule magnets: a solution NMR spectroscopic and DFT study

Chemistry. 2015 Oct 5;21(41):14421-32. doi: 10.1002/chem.201501944. Epub 2015 Aug 19.

Authors

Marko Damjanović¹, Takaumi Morita², Keiichi Katoh^{2

3}, Masahiro Yamashita^{2

3}, Markus Enders⁴

Affiliations

¹ Institute of Inorganic Chemistry, University of Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg (Germany), Fax: (+49) 6221-54-161-6247.
² Department of Chemistry, Graduate School of Science, Tohoku University, 6-3 Aramaki-Aza-Aoba, Sendai 980-8578 (Japan).
³ CREST, JST, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012 (Japan).
⁴ Institute of Inorganic Chemistry, University of Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg (Germany), Fax: (+49) 6221-54-161-6247. markus.enders@uni-heidelberg.de.

PMID: 26288225
DOI: 10.1002/chem.201501944

Abstract

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 (1) H, (13) C 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 (1) H and (13) 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)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.

Keywords: lanthanoids; paramagnetic NMR; phthalocyanines; single molecule magnets.