Seven-Coordinate Tb3+ Complexes with 90% Quantum Yields: High-Performance Examples of Combined Singlet- and Triplet-to-Tb3+ Energy-Transfer Pathways
authors Aquino, LED; Barbosa, GA; Ramos, JD; Giese, SOK; Santana, FS; Hughes, DL; Nunes, GG; Fu, LS; Fang, M; Poneti, G; Neto, ANC; Moura, RT; Ferreira, RAS; Carlos, LD; Macedo, AG; Soares, JF
nationality International
journal INORGANIC CHEMISTRY
keywords LUMINESCENT LANTHANIDE COMPLEXES; MOLECULAR-ORBITAL METHODS; ION MAGNET; SPECTROSCOPIC PROPERTIES; COORDINATION-COMPOUNDS; CRYSTAL-STRUCTURES; METAL-IONS; BASIS-SET; EMISSION; LIGANDS
abstract Seven-coordinate, pentagonal-bipyramidal (PBP) complexes [Ln(bbpen)Cl] and [Ln(bbppn) Cl], in which Ln = Tb3+ (products I and II), Eu3+ (III and IV), and Gd3+ (V and VI), with bbpen(2-) = N,N'-bis(2-oxidobenzyl)-N,N'-bis(pyridin-2-ylmethyl)-ethylenediamine and bbppn(2-) = N,N'-bis(2-oxidobenzyl)-N,N'-bis(pyridin-2-ylmethyl)-1,2-propanediamine, were synthesized and characterized by single-crystal X-ray diffraction analysis, alternating-current magnetic susceptibility measurements, and photoluminescence (steady-state and time-resolved) spectroscopy. Under a static magnetic field of 0.1 T, the Tb3+ complexes I and II revealed single-ion-magnet behavior. Also, upon excitation at 320 nm at 300 K, I and II presented very high absolute emission quantum yields (0.90 +/- 0.09 and 0.92 +/- 0.09, respectively), while the corresponding Eu3+ complexes III and IV showed no photoluminescence. Detailed theoretical calculations on the intramolecular energy-transfer rates for the Tb3+ products indicated that both singlet and triplet ligand excited states contribute efficiently to the overall emission performance. The expressive quantum yields, Q(Ln)(L), measured for I and II in the solid state and a dichloromethane solution depend on the excitation wavelength, being higher at 320 nm. Such a dependence was rationalized by computing the intersystem crossing rates (W-ISC) and singlet fluorescence lifetimes (tau(S)) related to the population dynamics of the S-1 and T-1 levels. Thin films of product II showed high air stability and photostability upon continuous UV illumination, which allowed their use as downshifting layers in a green light-emitting device (LED). The prototypes presented a luminous efficacy comparable with those found in commercial LED coatings, without requiring encapsulation or dispersion of II in host matrixes. The results indicate that the PBP environment determined by the ethylenediamine (en)-based ligands investigated in this work favors the outstanding optical properties in Tb3+ complexes. This work presents a comprehensive structural, chemical, and spectroscopic characterization of two Tb3+ complexes of mixed-donor, en-based ligands, focusing on their outstanding optical properties. They constitute good molecular examples in which both triplet and singlet excited states provide energy to the Tb3+ ion and lead to high values of Q(Ln)(L).
publisher AMER CHEMICAL SOC
issn 0020-1669
isbn 1520-510X
year published 2021
volume 60
issue 2
beginning page 893
ending page 908
digital object identifier (doi) 10.1021/acs.inorgchem.0c03020
web of science category 16
subject category Chemistry, Inorganic & Nuclear
unique article identifier WOS:000643574200042

Apoio

1suponsers_list_ciceco.jpg