Syntheses,Structures And Properties Of Lanthanide(?) Coordination Complexes Based On The Aromatic Selenites

In recent years,metal-organic coordination complexes have attracted more and more attention,not only because they have various structures,but also due to their potential applications in gas storage/adsorption,catalysis,separation and pharmaceuticals.Therefore,the design and syntheses of metal-organic coordination complexes with unique structures and practical value has become an important research topic at moment.As a branch of the coordination complexes,lanthanide?III?coordination complexes are favored by researchers due to their unique magnetic and fluorescent properties.carboxylic acid ligands have various coordination modes and strong coordination ability which can form stable lanthanide coordination complexes with lanthanide metals,and carboxylate-based lanthanide coordination complexes have potential applications in many aspects such as magnetic and fluorescent properties.The coordination mode and coordination ability of aromatic selenite are similar to those of carboxylate,and there are few studies on the structures and properties of lanthanide coordination complexes based on aromatic selenite.In this paper,sixteen novel lanthanide coordination complexes based on aromatic seleninic acids,which containing 3,4,5-trifluorophenylseleninic acid,phenylseleninic acid and 4-fluorophenylseleninic acid,were synthesized under hydrothermal and natural volatilization method.The complexes were characterized by X-ray single crystal diffraction,elemental analysis,infrared spectroscopy?IR?and XRD powder diffraction.The magnetic properties,thermal stability and fluorescence properties of the most complexes were investigated.The main work of this paper is summarized as follows three points:1.Four novel lanthanide coordination complexes,[Ln₂?L?₆?DMF?]_n?L=3,4,5-trifluorobenzeneselenite Ln=Nd?1?,Tb?2?,Dy?3?,Ho?4??were synthesized by hydrothermal reaction of 3,4,5-trifluorobenzene selenite with lanthanide?III?ions.Under the analysis of X-ray single crystal diffraction,complexes 1-4 are isostructural and all showed 1D Zig-zag chain structure.The thermogravimetric analyses of complexes 1-4under nitrogen atmosphere which show that complexes 1-4 have high thermal stability.The solid-state luminescence property of complex 2 was studied at room temperature and it exhibited strong green fluorescence emission in the visible region and the fluorescence lifetime of complex 2 reached 1.54 ms.In addition,the magnetic properties of complexes3 and 4 were tested under 1.8-300 K which show that complexes 3 and 4 exhibit weak antiferromagnetic interactions between lanthanide ions.2.Five novel lanthanide coordination complexes,[Ln₂?L?₂?phen?₄?NO₃?₄](phen=1,10-phenanthroline,L=phenylselenite,Ln=Nd?5?,Gd?6?[Ln₂?L?₄?phen?₂?NO₃?₂]?Ln=Tb?7?,Dy?8?,Er?9??,were prepared by reacting benzene selenite and N-ancillary ligand?phen?with lanthanide?III?ions at room temperature.The single crystal structure characterization showed that complexs 5 and 6 are isostructural and complexes 7-9 are isostructural,respectively,and they are dinuclear monomolecular structure.Adjacent molecules in compounds 5-9 form one-dimensional chain-like and two-dimensional layered supramolecular structure by C-H···O hydrogen bonding interactions,respectively.The solid-state photoluminescence property of complex 7 was studied at room temperature and it exhibited strong green fluorescence emission of the Tb^IIIin the visible region,and the luminescence lifetime of complex 7 reached 1.23 ms.In addition,the magnetic properties of complexes 7-8 were tested under 1.8-300 K which show that complexes 7-8 exhibit weak antiferromagnetic interaction.Furthermore,the complex 8displays double relaxation single molecule magnetic behavior.3.Seven novel lanthanide coordination complexes,[Ln₂?L?₂?phen?₄?NO₃?₄]?L=4-fluorobenzeneselenite,phen=1,10-phenanthroline,Ln=Nd?10?,Sm?11?,Eu?12??,[Ln₂?L?₂?phen?₂?NO₃?₂]?Ln=Tb?13?,Dy?14?,Ho?15??and[Er?L?₄?phen??NO₃?]_n?16?were designed and synthesized by 4-fluorophenylselenite and N-auxiliary ligand with lanthanide?III?ions at room temperature.Structural characterization show that complexes10-12 are isostructual and complexes 13-15 are isostructual.Adjacent molecules in compounds 10-15 form one-dimensional chain-like and two-dimensional supramolecular structure through the C-H···F hydrogen bonding interactions,respectively.Complex 16is a one-dimensional chain-like structure which further connected to two-dimensional layered supramolecular structure by C-H···F hydrogen bonding interactions.The solid-state photoluminescence property of complex 12 was studied at room temperature and it exhibited strong red fluorescence emission of the central metal Eu^IIIin the visible region and the luminescence lifetime of complex 12 reached 0.76 ms.Moreover,the magnetic properties of complexes 13-14 were tested under 1.8-300 K which show that complexes 13-14 exhibit ferromagnetic interactions.