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Three-dimensional porous metal-radical frameworks based on triphenylmethyl radicals

Abstract:

Lanthanide coordination polymers {[Ln(PTMTC)(EtOH)2H 2O]̇xH2O, yEtOH} [Ln=Tb (1), Gd (2), and Eu (3)] and {[Ln(αH-PTMTC)(EtOH)2H2O]̇xH2O, yEtOH} [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-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)̇(4 4.62.85.104) 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-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 1-3 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. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.