Cyclometallated platinum(ii) complexes containing NHC ligands: synthesis, characterization, photophysics and their application as emitters in OLEDs

Abstract

A series of novel luminescent NHC Pt(ii) complexes has been synthesized, characterized and used to prepare green OLEDs.

Luminescent Platinum(IV) Complexes Bearing Cyclometalated 1,2,3‐Triazolylidene and Bi‐ or Terdentate 2,6‐Diarylpyridine Ligands

“…The lowest‐energy feature in the spectra of complexes cis / trans ‐ C , C *‐ 3 covers the range 360–450 nm and appears to include several absorptions, the intensity and energy of which are typical of the primarily 1 MLCT transitions usually observed for Pt II complexes with cyclometalated arylpyridine ligands . Similar absorptions have been observed for related complexes of the type cis ‐ C , C* ‐[PtCl(C^N)(L)], where C^N is a cyclometalated 2‐arylpyridine and L represents a 2‐imidazolylidene ligand …”

“…Complex cis ‐ C , C *‐ 3 presents the highest k nr value of the studied series in CH 2 Cl 2 at 298 K and a lower than expected k r value, resulting in a very weak emission. Related complexes of the type cis‐C , C* ‐[PtCl(C^N)(L)] exhibit quantum yields in the range Φ =0.054–0.079 in the same medium …”

“…[68] Similar absorptions have been observed for related complexes of the type cis-C,C*-[PtCl(C^N)(L)],w here C^N is a cyclometalated 2-arylpyridine and Lr epresents a2 -imidazolylidene ligand. [69] The main features observed in the spectrum of 4 are typical of complexes of the type [Pt(C^N^C)L]. [70][71][72] The moderately intense absorptions in the range 330-400 nm can mainly be ascribed to 1 LC transitions within the dtpy ligand,a nd the long tail in the range 400-500nmt ot he primarily 1 MLCT transitions involving the same ligand.…”

Shedding light on the photophysical properties of newly designed platinum(II) complexes by adding substituents on functionalized ligands as highly efficient OLED emitters from a theoretical viewpoint

“…In contrast, phosphorescent transition metal complexes as triplet dopant emitters would harvest both the singlet and triplet excitons as light due to the efficient intersystem crossing (ISC) via spineorbit coupling (SOC) induced by the transition metal ions, so PHOLEDs could exhibit near-unity internal electroluminescence quantum efficiency [5]. In this area, d 6 transition-metal based complexes, e.g., Ir(III) species or d 8 transition-metal based complexes, e.g., Pt(II) species have attracted extensive interest due to their prominent advantages of the stability in various media and under different conditions and easily tunable emission energy by the modulation in the electronic and structural characteristics of the ligands [6].…”

DFT/TDDFT insight into the impact of ring size of the NHC chelating unit of high effective phosphorescent Platinum (II) complexes

“…Recently, as a typical of deep blue phosphorescent material, cyclometalated N‐heterocyclic carbene (NHC)‐based transition metal complexes have obtained a great deal of attention in the field of organic light‐emitting diodes (OLEDs) . In general, the NHC ligands stand out among all the coordinated ligands because they are in possession of strong σ‐bonding, simply tunable steric as well as extraordinary electronic properties.…”