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

Abstract

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 [LnLH(DMF)3][(4-NH2Ph)3C](NO3)(CH3CO2H), where Ln=Gd (OnG5-Gd), Tb (OnG5-Tb), Dy (OnG5-Dy), and LH3−= 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 LHH3 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.