posted on 2016-06-07, 00:00authored bySara Fuertes, Andrés
J. Chueca, Mariano Perálvarez, Pilar Borja, Marc Torrell, Josep Carreras, Violeta Sicilia
We
report on the generation of bright white luminescence through
solid-state illumination of remote phosphors based on novel cycloplatinated
N-heterocyclic carbene (NHC) compounds. Following a stepwise protocol
we got the new NHC compound [{Pt(μ-Cl)(C∧C*)}2] (4) (HC∧C*-κC* = 1-(4-(ethoxycarbonyl)phenyl)-3-methyl-1H-imidazol-2-ylidene), which was used together with the
related ones 4a (HC∧C*-κC*= 1-(4-cyanophenyl)-3-methyl-1H-imidazol-2-ylidene) and 4b (HC∧C*-κC*=
3-methyl-1-(naphthalen-2-yl)-1H-imidazol-2-ylidene)
as starting materials for the synthesis of the new ionic derivatives
[Pt(R-C∧C*) (CNR′)2]PF6 (R = −COOEt,
R′ = t-Bu (5), Xyl (6); R = −CN, R′ = t-Bu (7), Xyl (8); R∧C = Naph, R′ = t-Bu (9), Xyl (10)). The X-ray structures
of 6 and 8–10 have been
determined. The photophysical properties of these cationic compounds
have been studied and supported by the time-dependent-density functional
theory (TD-DFT) calculations. The compounds 5, 8, and 9 have been revealed as the most efficient
emitters in the solid state with quantum yields of 41%, 21%, and 40%,
respectively. White-light remote-phosphors have been prepared just
by stacking different combinations of these compounds and [Pt(bzq)
(CN) (CNtBu)] (R1) as blue
(5, 8), yellow (9), and red
(R1) components onto the same substrate. The CCT (correlated
color temperature) and the CRI (color rendering index) of the emitted
white-light have been tuned by accurately controlling the individual
contributions.