Ferromagnetic versus antiferromagnetic exchange interactions in tetrathiafulvalene-based 3d/4f heterobimetallic complexes

Goulven Cosquer, Fabrice Pointillart, Yann Le Gal, Stéphane Golhen, Olivier Cador, Lahcène Ouahab

Research output: Contribution to journalArticlepeer-review

35 Citations (Scopus)

Abstract

(TTF-salphen)M compounds (TTF-salphen2-=4,5-bis(propylthio) tetrathiafulvalene-N,N′-phenylenebis(salicylideneimine) dianion; M=Cu II and NiII) have been treated with Ln(hfac) 3·2 H2O precursors (hfac-=1,1,1,5,5,5- hexafluoroacetylacetonate anion; Ln=GdIII, TbIII, and DyIII) to elaborate unprecedented 3d/4f TTF-based heterobimetallic complexes of formula [(TTF-salphen)MLn(hfac)3]. All the structures of these compounds have been resolved by X-ray diffraction on single crystals. The structures of these complexes are formed by a TTF-salphen2- ligand coordinated to the 3d metal ions in the inert tetradentate N2O 2 site. The Ln(hfac)3 fragment is coordinated to the (TTF-salphen)M one through the two phenolate bridges. Even if the complexes are similar in both CuII and NiII families, the crystal packing is different. In the first case, dimers of TTF-salphen2- donors constitute the organic network. In the other case, a reminiscent organic network is observed with S⋯S contacts. The photophysical properties of [(TTF-salphen)CuDy(hfac)3] (3) in chloroform solution highlight the redshift of the TTF→salphen charge transfer (400 cm-1) relative to the analogue excitations in (TTF-salphen)Cu, which attest to the stability of these structures in solution. Static magnetic measurements have allowed us to quantify the ferromagnetic interactions (J=+1.29 cm-1) between CuII and GdIII in the [(TTF-salphen)CuGd(hfac) 3] complex. Finally, an empirical method that consists of the comparisons of the magnetic properties of [(TTF-salphen)CuTb(hfac)3] with [(TTF-salphen)NiTb(hfac)3] and [(TTF-salphen)CuDy(hfac) 3] with [(TTF-salphen)NiDy(hfac)3] has established that ferromagnetic interactions take place between CuII and Tb III ions, whereas unusual antiferromagnetic interactions have been identified between CuII and DyIII ions. Perfect partners: Tetrathiafulvalene-based 3d/4f heterobimetallic complexes have been crystallized. Their photophysical properties demonstrate the coordination effect of the 4f lanthanides and the stability of the complexes in solution. Empirical methods have been used to determine that ferromagnetic interactions take place in the Cu/Gd and Cu/Tb pairs, while antiferromagnetic interactions are found for Cu/Dy pairs (see picture).

Original languageEnglish
Pages (from-to)12502-12511
Number of pages10
JournalChemistry - A European Journal
Volume17
Issue number44
DOIs
Publication statusPublished - 2011 Oct 24

Keywords

  • lanthanides
  • magnetic properties
  • photophysics
  • tetrathiafulvalene
  • transition metals

ASJC Scopus subject areas

  • Catalysis
  • Organic Chemistry

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