Influence of thermally induced structural transformations on the magnetic and luminescence properties of tartrate-based chiral lanthanide organic-frameworks

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Materials for optical and electronic devices, 2020-06, Vol.8 (24), p.8243-8256
• Main Authors: Huizi-Rayo, Uxua, Zabala-Lekuona, Andoni, Terenzi, Alessio, Cruz, Carlos M, Cuerva, Juan M, Rodríguez-Diéguez, Antonio, García, Jose Angel, Seco, José M, San Sebastian, Eider, Cepeda, Javier
• Format: Article
• Language: English
• Subjects: Circular polarization; Crystallography; Data collection; Dehydration; Dichroism; Dysprosium; Emitters; Erbium; Low temperature; Luminescence; Magnetic measurement; Magnetic properties; Metal-organic frameworks; Optical properties; Photoluminescence; Room temperature; Synthesis; Terbium; Thermogravimetry; Water chemistry
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/d0tc00736f

This work reports on the synthesis and characterization of five enantiomeric pairs of isostructural 3D metal-organic frameworks (MOFs) with the general formula {[Ln 2 (μ 4 -tar) 2 (μ-tar)(H 2 O) 2 ]· x H 2 O} n [where Ln( iii ) = Tb ( Tb-L and Tb-D ), Dy ( Dy-L and Dy-D ), Ho ( Ho-L and Ho-D ), Er ( Er-L and Er-D ) and Tm ( Tm-L and Tm-D ); tar = tartrate ( d - or l -) and x = 3 or 4 depending on the counterpart], which possess interesting luminescence and magnetic properties. These MOFs undergo progressive and reversible dehydration processes upon controlled heating yielding three crystalline phases ( Ln-L′ , Ln-L′′ and Ln-L′′′ ). Alternating current magnetic measurements on Tb, Dy and Er-based compounds exhibit field induced single-molecule magnet behavior dominated by QTM, which is partially suppressed when diluted on a Y-based matrix. Tartrate ligands show poor room temperature sensitization of Tb and Dy centers that is enhanced at low temperature (10 K), even enabling weak Tm-based emission. More interestingly, the dehydration modulates both magnetic and photoluminescence properties on the basis of both the distortions occurring in the coordination shells and a decrease of water molecules acting as quenchers, respectively, endowing these materials with potential humidity sensing capacity. Remarkably, the Tb-based MOF shows circularly polarized luminescence (CPL), being one of the examples of this very scarce family of CPL emitters reported so far. Chiral 3D microporous lanthanide and tartrate-based MOFs with thermally induced modulation of magnetic/luminescence properties and chiroptical activity.