ic6b02826_si_002.cif (4.09 MB)
Heteroleptic Cycloplatinated N‑Heterocyclic Carbene Complexes: A New Approach to Highly Efficient Blue-Light Emitters
dataset
posted on 2017-04-07, 13:20 authored by Sara Fuertes, Andrés J. Chueca, Lorenzo Arnal, Antonio Martín, Umberto Giovanella, Chiara Botta, Violeta SiciliaNew heteroleptic compounds of platinum(II)-containing cyclometalated
N-heterocyclic carbenes, [PtCl(R-C^C*)(PPh3)] [R-CH^C*-κC*
= 3-methyl-1-(naphthalen-2-yl)-1H-imidazol-2-ylidene
(R-C = Naph; 1A), 1-[4-(ethoxycarbonyl)phenyl]-3-methyl-1H-imidazol-2-ylidene (R = CO2Et; 1B), and [Pt(R-C^C*)(py)(PPh3)]PF6 (py = pyridine;
R-C = Naph, 2A; R = CO2Et, 2B], have been prepared and fully characterized. All of them were obtained
as the trans-(C*,PPh3) isomer in high
yields. The selectivity of their synthesis has been explained in terms
of the degree of transphobia (T) of pairs of ligands in trans positions.
X-ray diffraction studies on both 2A and 2B revealed that only in 2A, containing a C^C* with a
more extended π system, do the molecules assemble themselves
into head-to-tail pairs through intermolecular π···π
contacts. The photophysical properties of 2A and 2B and those of the related compounds [Pt(NC-C^C*)(PPh3)L]PF6 [NC-CH^C*-κC* = 1-(4-cyanophenyl)-3-methyl-1H-imidazol-2-ylidene; L = pyridine (py; 2C),
2,6-dimethylphenylisocyanide (CNXyl; 3C), and 2-mercapto-1-methylimidazole
(MMI; 4C)] have been examined to analyze the influence
of the R substituent on R-C^C* (R-C = Naph; R = CO2Et,
CN) and that of the ancillary ligands (L) on them. Experimental data
and time-dependent density functional theory calculations showed the
similarity of the electronic features associated with R-C^C* (R =
CN, CO2Et) and their difference with respect to R-C^C*
(R-C = Naph). All of the compounds are very efficient blue emitters
in poly(methyl methacrylate) films under an argon atmosphere, with
QY values ranging from 68% (2B) to 93% (2C). In the solid state, the color of the emission changes to yellowish-orange
for compounds 2A (λmax = 600 nm) and 3C (λmax = 590 nm) because of the formation
of aggregates through intermolecular π···π
interactions. 2C and 3C were chosen to fabricate
fully solution-processed electroluminescent devices with blue-light
(2C), yellow-orange-light (3C), and white-light
(mixtures of 2C and 3C) emission from neat
films of the compounds as emitting layers.
