Lanthanoid/Alkali Metal β-Triketonate Assemblies: A Robust Platform for Efficient NIR Emitters.
The reaction of hydrated lanthanoid chlorides with tribenzoylmethane and an alkali metal hydroxide consistently resulted in the crystallization of neutral tetranuclear assemblies with the general formula [Ln(Ae⋅HOEt)(L)4 ]2 (Ln=Eu(3+) , Er(3+) , Yb(3+) ; Ae=Na(+) , K(+) , Rb(+) ). Analysis of the crystal structures of these species revealed a coordination geometry that varied from a slightly distorted square antiprism to a slightly distorted triangular dodecahedron, with the specific geometrical shape being dependent on the degree of lattice solvation and identity of the alkali metal. The near-infrared (NIR)-emitting assemblies of Yb(3+) and Er(3+) showed remarkably efficient emission, characterized by significantly longer excited-state lifetimes (τobs ≈37-47 μs for Yb(3+) and τobs ≈4-6 μs for Er(3+) ) when compared with the broader family of lanthanoid β-diketonate species, even in the case of perfluorination of the ligands. The Eu(3+) assemblies show bright red emission and a luminescence performance (τobs ≈0.5 ms, ${{\Phi}{{{\rm L}\hfill \atop {\rm Ln}\hfill}}}$≈35-37 %, ηsens ≈68-70 %) more akin to the β-diketonate species. The results highlight that the β-triketonate ligand offers a tunable and facile system for the preparation of efficient NIR emitters without the need for more complicated perfluorination or deuteration synthetic strategies.
Department of Chemistry and Nanochemistry Research Institute, Curtin University, Kent Street, Bentley 6102 WA (Australia).
Brodie L
BL
Reid
Department of Industrial Chemistry "Toso Montanari", University of Bologna, viale del Risorgimento 4, Bologna 40136 (Italy).
Stefano
S
Stagni
Laboratory of Micro and Submicro Enabling Technologies of the Emilia-Romagna Region S.c.r.l. (MIST E-R S.c.r.l.), via Gobetti 101, 40129 Bologna (Italy).
Joanna M
JM
Malicka
Laboratory of Micro and Submicro Enabling Technologies of the Emilia-Romagna Region S.c.r.l. (MIST E-R S.c.r.l.), via Gobetti 101, 40129 Bologna (Italy).|Institute for Organic Synthesis and Photoreactivity, CNR, via Gobetti 101, 40129 Bologna (Italy).
Massimo
M
Cocchi
Centre for Microscopy, Characterisation and Analysis, University of Western Australia, Crawley 6009 WA (Australia).
Alexandre N
AN
Sobolev
Centre for Microscopy, Characterisation and Analysis, University of Western Australia, Crawley 6009 WA (Australia).
Brian W
BW
Skelton
School of Chemistry and Molecular Biosciences, University of Queensland, St Lucia 4072 QLD (Australia).
Evan G
EG
Moore
Department of Chemistry,D-600 Université de Montréal, 2900 Edouard-Montpetit Montréal, Quebec (Canada).
Garry S
GS
Hanan
Department of Chemistry and Nanochemistry Research Institute, Curtin University, Kent Street, Bentley 6102 WA (Australia). m.ogden@curtin.edu.au.
Mark I
MI
Ogden
Department of Chemistry and Nanochemistry Research Institute, Curtin University, Kent Street, Bentley 6102 WA (Australia). m.massi@curtin.edu.au.
Massimiliano
M
Massi
diketonates; lanthanides; luminescence; near-infrared emitters; triketonates