Reticular three-dimensional 3d-4f frameworks constructed through substituted imidazoledicarboxylate: syntheses, luminescence and magnetic properties study.

A family of heteronuclear metal organic frameworks (MOFs) using lanthanide and transition metal ion based on a rigid ligand of substituted imidazoledicarboxylic acid, namely, {[Ln2Zn2 (|3-Hmimda)2 (μ₃-mimda)₂-4H₂O]_n-mn H₂O}, Ln = Nd, m = 2 (1), Ln = Ho, m = 3 (2), Ln = Er, m = 2 (3), Ln = Yb, m = 3 (4), [Tb₂Co₂(μ₃-Hmimda)2 (μ₃-mimda)2-4H₂O]_n-2nH₂O} (5) and [Dy₂Co₂ (μ₃-Hmimda)₂ (μ₃-mimda)₂-4H₂O]_n-nH₂O} (6), (H₃mimda = 1H-2-methyl-4,5-imidazole-dicarboxylic acid), have been developed and characterized. All the complexes (except for a little disparity for 1) are isostructural, and all crystallize in the monoclinic system. They possess an extended reticular-like porous structure constructed from corrugated 2D layers. Direct current (dc) magnetic susceptibility measurements for 1 - 5 indicated depopulation of the Stark components at low temperature and/or possible weak anti-ferromagnetic interactions within heteronuclear MOFs. Alternating current (ac) susceptibility studies reveal that the Dy(iii)--Co(ii) complex exhibits both possible ferromagnetic couplings and frequency-dependent out-of-phase signals, behaviour of single-ion magnet nature. Fluorescence properties of series complexes both in near-infrared (NIR) and visible regions have been comparatively studied. [ABSTRACT FROM AUTHOR]