New heteroleptic compounds of platinum(II)-containing cyclometalated N-heterocyclic carbenes, [PtCl(R-C^C*)(PPh)] [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 = COEt; 1B), and [Pt(R-C^C*)(py)(PPh)]PF (py = pyridine; R-C = Naph, 2A; R = COEt, 2B], have been prepared and fully characterized. All of them were obtained as the trans-(C*,PPh) 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*)(PPh)L]PF [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 = COEt, 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, COEt) 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 (λ = 600 nm) and 3C (λ = 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.

New cycloplatinated N-heterocyclic carbene (NHC) compounds with chelate diphosphines (P^P) as ancillary ligands: [Pt(R-C^C*)(P^P)]PF6 (R = H, P^P = dppm 1A, dppe 2A, dppbz 3A; R = CN, P^P = dppm 1B, dppe 2B, dppbz 3B) have been prepared from the corresponding starting material [{Pt(R-C^C*)(µ-Cl)}2] (R = H, A, R = CN, B) and fullycharacterized. The new compound A has been prepared by a stepwise protocol. The photophysical properties of 1A-3A and 1B-3B have been widely studied and supported by the time-dependent-density functional theory (TD-DFT). These compounds show an efficient blue (dppe, dppbz) or cyan (dppm) emission in PMMA films (5%wt), with photoluminescence quantum yield (PLQY) ranging from 30% to 87% under argon atmosphere. This emission has been assigned mainly to transitions from 3 ILCT [π(NHC) → 2 π*(NHC)] excited states with some 3 LL'CT [π(NHC) → π*(P^P)] character. The electroluminescence of these materials in proof-of-concept solution processed OLEDs containing 3A and 3B as dopants was investigated. The CIE coordinates for devices based on 3A (0.22, 0.41) and 3B (0.24, 0.44) fit within the sky blue region. raise the energy of the MC states hindering their photo-or thermal population and then increasing the emission quantum yield and avoiding degradation via bond-breaking processes. 20, 23 The use of didentate cyclometalated carbenes (C^C*) allows to tune the emission properties by changing the nature of both, the C^C* and the ancillary ligands. In this field high efficient blue-emitters have been reported by our group. [19][20][21][22] Those containing chelate diphosphines, such as [Pt (R-C^C*)(P^P)] PF6 (R-C= Naph, R =CO2Et, P^P: dppm (diphenylphosphinomethane), dppe (diphenylphosphinoethane), dppbz (1,2diphenylphosphino-benzene) showed high photoluminescence quantum yields (PLQY) and stability and were proved as the active components in photo-and electroluminescent devices. 21 OLEDs can be manufactured with either vacuum deposition or solution-processing techniques. The former method is suitable for small molecules that, generally, have better performance and longer stability due to the purity of the sublimated samples. [24][25][26] Vacuum deposition, however, requires accurate control on doping concentration and wastes lot of material thereby increasing the manufacturing costs. 27 Recent developments on solutionprocessable OLEDs based on small molecules have focused on optimizing efficiency while using simple processing techniques. 27 However, there are still limited examples, in particular for solution-processable OLEDs based on Pt(II) complexes. 25,26,[28][29][30][31][32][33][34][35][36][37][38][39][40] Within this perspective we decided to extend the family of [Pt(R-C^C*)(P^P)]PF6 compounds by changing the C^C* group. As result, herein we report the synthesis and the structural properties of compounds [Pt (R-C^C*)(P^P)]PF6 (R= H, P^P: dppm 1A, dppe 2A, dppbz 3A; R = CN, P^P: dppm 1B, dppe 2B, dppbz 3B). The photophysical and TD-DFT studies were also carried out, showing photoluminescence...

The new compounds [Pt(R-C^C*)(P^P)]PF6 as blue or orange emitters were combined with the red emitter [Pt(bzq)(CN)(CNXyl)] to fabricate two-component WOLEDs and pcWLEDs. They rendered warm white light with optimal CRI and Duv values and a great range of nominal CCT: 4000 K–2000 K.