Two novel lanthanide metal–organic frameworks (Ln-MOFs), formulated as {[Ln2(L2)2(H2O)5]·3H2O} n (Nd 1 and Eu 2) has been acquired under hydrothermal conditions, in which H3L2 ligand was derived from in situ decarboxylation reaction of H4L1 ligand (H3L2 = 5-(3′,5′-dicarboxylphenyl)­picolinic acid, H4L1 = 3-(3′,5′-dicarboxyphenyl)­pyridine-2,6-dicarboxylic acid). Both compounds possess (3,4,7)-connected 3,4,7T22 topology with a schläfli symbol of {43}­{45·6}­{48·69·84}. Compound 2 displays excellent luminescence properties and exhibits good stability in water and other common organic solvents. In particular, 2 can detect Cu2+ ion, MnO4 – anion, and nitrobenzene with a high sensitivity and selectivity through the fluorescence quenching effect. Thus, 2 can be dressed up as a prospective luminescent sensor for detecting Cu2+, MnO4 –, and nitrobenzene.

Four new isostructural two-dimensional lanthanide(III)−metal organic frameworks (MOFs), namely, [Ln(L)(HCOO)(H 2 O)] n (Ln = Eu 1, Gd 2, Ho 3, and Tb 4, H 2 L = 5-((2′-cyano-[1,1′-biphenyl]-4-yl)methoxy)isophthalic acid), with a uninodal {4 4 .6 2 }-sql topology have been successfully isolated. Compounds 1 and 4 exhibit excellent applications as luminescent sensors for sensing benzaldehyde in methanol and Cr 3+ , CrO 4 2− , and Cr 2 O 72− in water with high sensitivity and selectivity based on luminescence quenching effects. Interestingly, 1 and 4 display excellent recyclable behaviors and can be recycled at least five times for sensing benzaldehyde, Cr(III) and Cr(VI) ions. These two compounds are the first multifunctional Ln−MOFs sensors for detecting benzaldehyde, Cr(III) and Cr(VI) ions, simultaneously. Therefore, these two materials may be excellent multifunctional recyclable luminescent sensors.

Functionalized nitronyl nitroxide biradical ligands incorporating pyridine groups hold Co and Ln ions together, creating biradical-based 3d-4f tetranuclear complexes [LnCo(hfac)(NITPhPybis)] [Ln = Gd (1), Tb (2), Dy (3), and Ho (4); NITPhPybis = 5-(4-pyridyl)-1,3-bis(1'-oxyl-3'-oxido-4',4',5',5'-tetramethyl-4,5-hydro-1 H-imidazol-2-yl)benzene; hfac = hexafluoroacetylacetonate]. These complexes have a centrosymmetric cyclic molecular structure in which two biradicals perform as tetradentate ligands to bind two Co and two Ln ions, resulting in a rare octaspin system. Direct-current (dc) magnetic susceptibility studies reveal that the strong antiferromagnetic Co-NO magnetic exchange dominates the present magnetic system, while magnetic coupling of Gd-ON is ferromagnetic. Analysis of the magnetic data of the Gd complex allows us to determine the magnetic parameters through the appropriate magnetic model. Alternating-current (ac) magnetic susceptibility investigations indicate that 2 displays frequency-dependent out-of-phase signals under a zero dc field, while ac magnetic susceptibilities of 3 show field-induced frequency dependence, which is a typical feature of slow relaxation of the magnetization. Complexes 1-4 represent the first nitronyl nitroxide biradical-based 3d-4f compounds.

The first examples of Ln-nitronyl nitroxide 1D chains based on the functionalized nitronyl nitroxide biradical have been obtained, and complexes Dy and Tb exhibit slow magnetic relaxation behavior.