Near-UV phosphorescent emitters: N-heterocyclic platinum(ii) tetracarbene complexes

Abstract

Although examples of nickel(ii), palladium(ii) and platinum(ii) N-heterocyclic tetracarbene complexes are known in the literature, particularly platinum(ii) tetracarbene complexes are rare. We developed a new synthetic route via biscarbene acetate complexes, which make homoleptic as well as heteroleptic platinum(ii) tetracarbene complexes accessible. The reported photoluminescence data show that these complexes have good quantum yields and photostability and are a promising class of emitters for PhOLEDs. Characterization of the compounds includes a solid-state structure of the homoleptic complex bis(1,1'-diisopropyl-3,3'-methylenediimidazoline-2,2'-diylidene)platinum(ii) dibromide.

Electronic Effects of para‐Substitution on the Melting Points of TAAILs

“…Deprotonation at the C2 carbon leads to the formation of N-heterocyclic carbenes which are frequently used ligands in many complexes. [35][36][37] It is also easily identifiable in the 1 H-and 13 C NMR spectra. Therefore, we chose these signals to probe the change in the electronic structure of the imidazolium core and observed changes of up to 0.3 ppm in the 1 H NMR shifts, and, in most cases, less than Dd = 1 ppm for the 13 C NMR shifts.…”

Blue phosphorescent platinum(ii) tetracarbene complexes with bis(triazoline-5-ylidene) ligands

“…The emission maximum of these complexes is shifted to the blue region around 435 nm, a shift of 50 nm compared to the tetracarbene complexes with bis(imidazole-2-ylidene) ligands published before (l em = 387 nm). 37, 38 To the best of our knowledge this is the first example where such a strong shift was observed for ligands with an imidazole/triazole core. One example from the literature (for completely different systems) describes shifts in opposite directions, another no effect at all.…”

“…Hence, the two different ligands lead to emission maxima at different wavelengths depending on the excitation wavelength. Based on the results obtained before 37, 38 we expect that the emission wavelength of 389 nm corresponds to the bis(imidazoline-2-ylidene), while the emission wavelength of 433 nm corresponds to the bis(1,2,4-triazoline-5-ylidene) ligand.…”

“…46,53 Recently, we described the syntheses and photophysical properties of homoleptic and heteroleptic platinum(II)(bis(imidazoline-2-ylidene)) 2 complexes. [36][37][38] In this study we varied the substituents R and R¢ (Fig. 1, I), but the emission wavelengths turned out to be independent from the type of alkyl substituent.…”

Isolation and Crystallographic Identification of Photoactive PtII Tris‐ and Bis(N‐methylbenzimidazole‐NHC) Complexes

“…[2b], Monodentate NHCs and bidentate bis(NHC) ligands have also been used as ancillary ligands in luminescent Pt II bis(acetylide)[4a], and cyclometallated complexes or as a linker between metal and an organic chromophore to form mono or di‐NHC Pt II complexes. Homoleptic and heteroleptic tetra‐NHC Pt II complexes also emit in the near UV or blue region . Among Pt II NHC complexes, there are only limited examples of tri‐NHC Pt II complexes and their photophysical property is still unknown.…”