Three-Dimensional Porous Metal-Radical Frameworks Based on Triphenylmethyl Radicals

Lanthanide coordination polymers {[Ln(PTMTC)(EtOH)2H2O]center dot xH2O, yEtOH} [Ln=Tb (1), Gd (2), and Eu (3)] and {[Ln(alpha H-PTMTC)(EtOH)2H2O]center dot 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 (alpha H-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 (4(2).8)center dot(4(4).6(2).8(5).10(4)) Schafli 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(alpha H-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.