Multimetal rare earth MOFs for lighting and thermometry: tailoring color and optimal temperature range through enhanced disulfobenzoic triplet phosphorescence

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Materials for optical and electronic devices, 2013-01, Vol.1 (39), p.6316-6324
• Main Authors: D'Vries, Richard F., Álvarez-García, Susana, Snejko, Natalia, Bausá, Luisa E., Gutiérrez-Puebla, Enrique, de Andrés, Alicia, Monge, M. Ángeles
• Format: Article
• Language: English
• Subjects: Cations; Color temperature; Construction; Emission; Ligands; Lighting; Optimization; Rare earth metals
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/c3tc30858h

New isostructural compounds [Ln sub(7)(3,5-DSB) sub(4)(OH) sub(9)(H sub(2)O) sub(15)].4H sub(2)O (Ln = Eu, Gd and Tb) (DSB = 3,5-disulfobenzoate), with excellent optical properties, have been obtained and studied. By combining the lanthanide cations with the DSB ligand the formation of a singular heptanuclear [Ln sub(7)(OH) sub(9)] super(+12) metallic core secondary building unit (SBU) has been promoted. This core is defined as a bi-capped dicubane SBU, and is a 4-connected node in a bidimensional net with (4 super(4).6 super(2) ) topology. The highly efficient emission from the triplet state of the disulfobenzoic ligand in the Gd-MOF and the exponential temperature dependence of I sub(Triplet)/I sub(Ln) = I sub(o) exp(-E sub(A)/k sub(B )T) allow the design of thermometers with different color ranges through the adequate multimetal combination that cover almost the whole visible spectrum and are useful in a wide temperature range (10-300 K) with unprecedented sensitivities up to 32% K super(-1). The Eu-DSB and Tb-DSB MOFs present an optimum antenna effect, a temperature independent f-f emission temporal decay and, in spite of the close packing of the Ln ions inside the MOF, no concentration quenching. The external efficiency is drastically increased in MOFs with a combination of a few percent of Eu and/or Tb with Gd by means of radiative and non-radiative energy transfers from the Gd ions and Gd connected ligands.