Two kinds of 2,4-dichlorobenzoate-based lanthanide coordination polymers tuned by 4,4′-bipyridine: Syntheses, structures, photoluminescence, and magnetism

Syntheses, Structures and Luminescent Properties of Eu- and Tb-MOFs with 3,5-Pyridinedicarboxylate and 1,2-Benzenedicarboxylate

Two lanthanide-based MOFs (Ln-MOFs) were synthesized by reaction of Eu(III) or Tb(III) perchlorates with mixed dicarboxylates of 3,5-pdc and 1,2-bdc (3,5-H₂pdc = 3,5-pyridinedicarboxylic acid; 1,2-H₂bdc = 1,2-benzenedicarboxylic acid) by hydrothermal method. The chemical formulas of the two complexes were [Eu₂(3,5-pdc)(1,2-bdc)₂(H₂O)₄]_n (1) and {[Tb₂(3,5-pdc)(1,2-bdc)₂(H₂O)₄]·2H₂O}_n (2). IR spectra and element analyses were tested to characterize the two compounds. The crystal structures were determined by X-ray single crystal diffraction. MOF 1 was 3D porous network structure but MOF 2 was 2D layered structure. The two MOFs emitted the characteristic fluorescence of Eu(III) or Tb(III) ion with the excitations of UV-rays. Their lifetimes of excited states for Eu(III) (⁵D₀) and Tb(III) (⁵D₄) were 0.31 and 0.82 ms. The absolute quantum yields (Ф_a) of MOF1 and 2 were also tested and the Ф_a(1) (λ_ex = 320 nm) and Ф_a(2) (λ_ex = 296 nm) were 15% and 48%, respectively.

Crystal Structures, Hirshfeld Surfaces, and Thermal Study of Isostructural Polymeric Ladders of La(III) and Sm(III) Coordination Compounds with 4,4'-Bipyridine and Dibromoacetates

Two novel mixed ligand complexes with general formula [M₂(4,4'-bpy)_1.5(CBr₂HCOO)₆(H₂O)₂]_n (where 4,4'-bpy = 4,4'-bipyridine) were synthesized. Thermal analysis was used to describe a solid intermediate and final products of thermolysis. A coupled TG-MS system was used to monitor principal volatile fragments evolved during pyrolysis. Crystal structures of the complexes were determined. Cationic dinuclear M₂ (M(III) = La, Sm) coordination cores were obtained. Both crystal structures are isostructural. Single crystal X-ray diffraction analysis revealed that investigated structures of 1D coordination polymers assembled in ladder-like systems. The central atom replacement resulted in unit cell identity parameter П = 0.0091. Additionally, the isostructurality of the reported La(III) and Sm(III) complexes was revealed using Hirshfeld Surface analysis supported by Enrichment Ratio calculations.