Heteronuclear {TbxEu1−x} furoate 1D polymers presenting luminescent properties and SMM behavior

Abstract

We report the synthesis, crystal structure and photo-magnetic properties of novel Tb/Eu polymeric complexes of general formula {TbxEu1−x(α-fur)3(H2O)3}n, supported by 2-furancarboxilic acid: the homonuclear Tb(III) complex {Tb} (1), four heterodinuclear complexes, {Tb0.8Eu0.2} (2), {Tb0.7Eu0.3} (3), {Tb0.3Eu0.7} (4), and {Tb0.1Eu0.9} (5), and the homonuclear Eu(III)-only complex {Eu} (6). X-ray diffraction experiments show that the α-furoate ligands, acting in bridging mode, consolidate the 1D polymeric chains along the c-axis. Luminescence studies show the sensitization capability of the furoic acid ligand. Color tuning from green to red can be successfully achieved through the heterodinuclear strategy. We have measured Eu emission by direct excitation at the resonant 7F0 → 5L6 (395 nm), and indirectly, by excitation of the non-resonant wavelength (280 nm) which provokes ligand → Tb → Eu energy transfer. Besides, ac susceptibility measurements under varying frequencies and temperatures reveal that mixed {TbxEu1−x} complexes exhibit field-induced slow relaxation dynamics, with extremely slow relaxation times, owing to direct processes affected by the bottleneck effect. Thus, the {TbxEu1−x} complexes represent interesting low-dimensional multifunctional materials combining both luminescent and SMM magnetic properties.