Stable N-heterocyclic carbene (NHC) cyclometalated (C^C) gold(iii) complexes as blue–blue green phosphorescence emitters

Abstract

Blue and blue-green phosphorescent Au(iii) compounds based on a novel C^C chelate ligand framework are reported.

Synthesis of New Donor‐Substituted Biphenyls: Pre‐ligands for Highly Luminescent (C^C^D) Gold(III) Pincer Complexes

“…Emission quantum yields F in dichloromethane solution at room temperature range between 3a nd 10 %b eing higher than the yields of many (C^N^C) analogues. [10] Obviously,t he quantum yields are not affected by the lateral donor of the pincer,b ut the ligand besides the pincer: The C 6 F 5 substituted systems 39 and 40 phosphoresce up to three times more efficient than the PhCC analogues 34 and 35.T his is especially noteworthy,s ince the opposite finding was reported by Venkatesan and co-workers aboutt he luminescence of cyclometalated [(C^N)Au III ] [64] and [(C^C')Au III ] [29] complexes. The authors found higher emission quantum yields for phenylethinyl substitutedc omplexes than for pentafluorophenyl substituted ones.…”

“…The emission spectra resemble the ones of other [(C^C^N)Au III ] [23] and [(C^N^C)Au III ]c omplexes [10,16] as well as biphenyl-based [(C^C)Au III ] [63] or cyclometalated pyridine [64] and carbene [(C^C')Au III ]c omplexes. [29] Thus, the p orbitalo ft he emissive p!p* 3 IL state is almost exclusively centred at the (bi)phenyl unit of the respective pincer ligand.…”

“…[28] There are no reports in the literature on gold(III) pincer complexes with two aryl donors andat hird donor other than pyridine (D = N), fore xample, carbene. However,b identate, (C^C') cyclometalated (C' = NHC carbon donor) Au III complexes were reportedb yv on Arx et al [29] and Crespoetal. [30] In the presents tudy,w er eport on the development of a synthetic access to 5,5-dimethyl-5H-dibenzo[b,d]stannoles (5) with ap yridine( D= N) or imidazolium (D = C') substituent in 4position, which are suitable precursors for the new Au III complexes 6 and 7 (Scheme 1).…”

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

“…[42,43] We anticipated that the donor properties of the triazolylidene moiety would benefit the emission efficiencies of cyclometalatedP t IV complexes by increasing the energy of deactivating excited states of LMCT character to ag reater extent than in the case of 2-arylpyridines. Cyclometalating aryl-NHC ligands have previously been employed for the synthesis of luminescentc omplexes of Ir III , [44][45][46][47][48][49][50][51][52] Pt II , [53][54][55][56] and Au III [57] with enhanced emission properties, often as non-chromophorics upporting ligands. However, most of them are normal 2-imidazolylidene-typea ryl-NHCs, whereas mesoionic aryl-NHCs have only been employed to prepare a limited number of luminescent Pt II complexeso ft he type [Pt(C^C*)(O^O)] (O^O = b-diketonate).…”

High Efficiency Sky‐Blue Gold(III)‐TADF Emitters**

“…Organogold(III) complexes with emission color towards the blue spectral region have been reported in the literature; for instance, in 2017, Venkatesan and co-workers reported gold(III) complexes constructed with NHC-containing C^C chelates that show vibronic-structured emission with maxima locating at~380-480 nm. [4] Yam and co-workersa lso reported blue gold(III) phosphors with photoluminescence maxima at~470-500 nm ande lectroluminescencem aximaa t~480-500nm. [1k-l, 5] However,v ibronically structured 3 IL excited states of gold(III) complexes have long emissionl ifetimes( tens to hundreds of microseconds), thus rendering these complexes unsuitablef or the fabrication of OLEDsw ithp ractical interest.…”