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Keywords:

  • lanthanides;
  • magnetism;
  • metal–organic frameworks;
  • porosity;
  • radicals

Abstract

Lanthanide coordination polymers {[Ln(PTMTC)(EtOH)2H2O]x H2O, y EtOH} [Ln=Tb (1), Gd (2), and Eu (3)] and {[Ln(αH[BOND]PTMTC)(EtOH)2H2O]x H2O, y EtOH} [Ln=Tb (1′), Gd (2′), and Eu (3′)] have been prepared by reacting LnIII ions with tricarboxylate-perchlorotriphenylmethyl/methane ligands that have a radical (PTMTC3−) or closed-shell (αH[BOND]PTMTC3−) character, respectively. X-ray diffraction analyses reveal 3D architectures that combine helical 1D channels and a fairly rare (6,3) connectivity described with the (42.8)⋅(44.62.85.104) Schäfli symbol. Such 3D architectures make these polymers porous solids upon departure of the non-coordinated guest-solvent molecules as confirmed by the XRD structure of the guest-free [Tb(PTMTC)(EtOH)2H2O] and [Tb(αH[BOND]PTMTC)(EtOH)2H2O] materials. Accessible voids represent 40 % of the cell volume. Metal-centered luminescence was observed in TbIII and EuIII coordination polymers 1′ and 3′, although the LnIII-ion luminescence was quenched when radical ligands were involved. The magnetic properties of all these compounds were investigated, and the nature of the {Ln–radical} (in 1 and 2) and the {radical–radical} exchange interactions (in 3) were assessed by comparing the behaviors for the radical-based coordination polymers 13 with those of the compounds with the diamagnetic ligand set. Whilst antiferromagnetic {radical–radical} interactions were found in 3, ferromagnetic {Ln–radical} interactions propagated in the 3D architectures of 1 and 2.