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=Eu3+, Er3+, Yb3+; 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 Yb3+ and Er3+ showed remarkably efficient emission, characterized by significantly longer excited-state lifetimes (?obs?37-47 ?s for Yb3+ and ?obs?4-6 ?s for Er3+) when compared with the broader family of lanthanoid ?-diketonate species, even in the case of perfluorination of the ligands. The Eu3+ assemblies show bright red emission and a luminescence performance (?obs?0.5 ms, equation image?35-37 %, ?sens?68-70 %) more akin to the ?-diketonate species. The results highlight that the ?-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.
Lanthanoid/Alkali Metal beta-Triketonate Assemblies: A Robust Platform for Efficient NIR Emitters
Cocchi Massimo;Cocchi Massimo;
2015
Abstract
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=Eu3+, Er3+, Yb3+; 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 Yb3+ and Er3+ showed remarkably efficient emission, characterized by significantly longer excited-state lifetimes (?obs?37-47 ?s for Yb3+ and ?obs?4-6 ?s for Er3+) when compared with the broader family of lanthanoid ?-diketonate species, even in the case of perfluorination of the ligands. The Eu3+ assemblies show bright red emission and a luminescence performance (?obs?0.5 ms, equation image?35-37 %, ?sens?68-70 %) more akin to the ?-diketonate species. The results highlight that the ?-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.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
