resumo
Photoluminescent isotypical phosphonate-based metal organic frameworks, [Ln(H(5)btp)]center dot 2H(2)O [where Ln(3+) = Tb3+ (1) or Gd3+ (2) and H(8)btp = [1,1'-biphenyl]-3,3',5,5'-tetrayltetrakis(phosphonic acid)] prepared under solvo(hydro)thermal conditions exhibit a three-dimensional supramolecular structure built up from phosphonate linkers bridging Li3+ ions. Single-crystal X-ray diffraction of 1 revealed hydrogen bonds along the a-axis between the crystallization water molecules and the phosphonate groups. The network features lozenge-shaped tubular channels with intermolecular interactions between adjacent organic ligand molecules. Crystal packing forces bring together two ligand biphenyl groups in a parallel arrangement, forming an excimer. A ratiometric luminescent thermometer operative close to room temperature was built based on the excimer and the D-5(4) -> F-7(5) Tb3+ emissions, exhibiting a maximum relative thermal sensitivity of 1.26%-K-1 and a minimum temperature uncertainty of 0.75 K at 319 K. This performance is similar to that of a thermometer based on the ligand singlet S-2,S-1 -> S-0 and metal D-5(4) -> F-7(5) transitions. Thus, the same MOF material provides two separate temperature data sets. This work shows the possibility of using excimer emissions in ratiometric luminescence thermometry.
palavras-chave
COORDINATION POLYMERS; LANTHANIDE PHOSPHONATES; NANOSCALE; MOLECULES; LINKER; RANGE; MOFS
categoria
Chemistry; Materials Science
autores
Ananias, D; Firmino, ADG; Mendes, RF; Paz, FAA; Nolasco, M; Carlos, LD; Rocha, J
nossos autores
Ana Daniela Gonçalves Firmino
Investigador
Duarte Ananias
Investigador Auxiliar
Filipe Alexandre Almeida Paz
Investigador Principal
João Rocha
Prof. Catedrático
Luís Carlos
Professor Catedrático
Mariela Martins Nolasco
Investigador Auxiliar
Ricardo Faria Mendes
Investigador JúniorGrupos
G1 - Materiais Porosos e Nanossistemas
G2 - Materiais Fotónicos, Eletrónicos e Magnéticos
G6 - Materiais Virtuais e Inteligência Artificial
agradecimentos
We thank Fundacao para a Ciencia e a Tecnologia (FCT, Portugal), the European Union, QREN, FEDER through Programa Operational Factores de Competitividade (COMPETE), CICECO - Aveiro Institute of Materials, POCI-01-0145-FEDER-007679 (FCT ref UID/CTM/50011/2013), financed by national funds through the FCT/MEC and when appropriate cofinanced by FEDER under the PT2020 Partnership Agreement. FCT is also gratefully acknowledged for Ph.D. Grants SFRH/BD/84495/2012 (to A.D.G.F.) and SFRH/BD/84231/2012 (to RF.M.) and postdoctoral research grant SFRH/BPD/95032/2013 (to D.A.).