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Lanthanoid/Alkali Metal β‐Triketonate Assemblies: A Robust Platform for Efficient NIR Emitters
Author(s) -
Reid Brodie L.,
Stagni Stefano,
Malicka Joanna M.,
Cocchi Massimo,
Sobolev Alexandre N.,
Skelton Brian W.,
Moore Evan G.,
Hanan Garry S.,
Ogden Mark I.,
Massi Massimiliano
Publication year - 2015
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201502536
Subject(s) - lanthanide , alkali metal , square antiprism , dodecahedron , luminescence , crystallography , chemistry , excited state , ligand (biochemistry) , metal , crystal structure , coordination geometry , materials science , molecule , ion , hydrogen bond , atomic physics , physics , organic chemistry , biochemistry , receptor , optoelectronics
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 ( τ obs ≈37–47 μs for Yb 3+ and τ obs ≈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 ( τ obs ≈0.5 ms, ${{\Phi}{{{\rm L}\hfill \atop {\rm Ln}\hfill}}}$ ≈35–37 %, η sens ≈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.