Lanthanide(III) Metal-Organic Frameworks (Ln=Gd, Tb, Dy) Based on a C₃ Symmetrical Tricarboxylate Linker

Lanthanide-based metal-organic frameworks have attracted significant interest due to their ability to combine porosity with one or more additional properties, providing an alternative method for the development of multifunctional materials. With this in mind, we report the synthesis and characterisation of the OnG5 family of MOFs with the formula [LnL_H(DMF)₃][(4-NH₂Ph)₃C](NO₃)(CH₃CO₂H), where Ln=Gd (OnG5-Gd), Tb (OnG5-Tb), Dy (OnG5-Dy), and L_H³⁻= the trianion of 4,4′,4′′-(1 E)-[4,4′,4′′-(methanetriyl)tris(benzene-4,1-diyl)tris(azan-1- yl-1-ylidene)]tris(methan-1-yl-1-ylidene)tribenzoic acid. OnG5 were synthesised in situ from the reaction of Ln(NO₃)₃.xH₂O, pararosaniline base [(4-NH₂Ph)₃COH] and terephthalaldehydic acid in DMF. Their structure was studied through single crystal x-ray crystallography and confirmed with DFT calculations. OnG5 display a 2D, three-fold interpenetrated structure with a honeycomb lattice topology. They are the first examples bearing the ligand L_HH₃ and they display photoluminescence originating from an intraligand π-π* or n-π* transition. Dc and ac magnetic susceptibility studies conducted on the OnG5-Gd analogue revealed an absence of magnetic interaction between the metal centres.