Ditopic bis-terdentate cyclometallating ligands and their highly luminescent dinuclear iridium(iii) complexes

Abstract

A new family of bridged cyclometallating ligands is reported, which incorporate two terdentate N(∧)C(∧)N-coordinating binding sites linked via pyrazine, pyrimidine or pyridazine units. Dinuclear Ir(III) complexes of one ligand have been prepared and crystallographically characterised; they display intense red phosphorescence.

Luminescent Diiridium Complexes with Bridging Pyrazolates: Characterization and Fabrication of OLEDs Using Vacuum Thermal Deposition

“…These, together with a series of diarylhydrazide‐bridged diiridium complexes, show strong intramolecular ππ stacking interaction to the second functional phenylpyridine‐based C^N chelates . On the contrary, the relevant diiridium complexes with a bis‐terdentate, pyrimidine‐based N^C^N‐N^C^N bridging chelate showed a larger k nr value and lowered photoluminescence Q.Y., confirming its being highly sensitive to the nature of coordination environment.…”

“…Moreover, this design also allowed adequate color tuning across the visible region, which is solely dependent of the dianionic phenyl–pyridine–pyrazole. For comparison, several ditopic chelates linked via pyrimidine, pyrazine and pyridazine, or functional 2‐phenylpyrimidine, diarylhydrazide, isocyanate, terpyridine dicarboxylate, and oxamidato based bridging ligands have been employed in the preparation of charge‐neutral luminescent diiridium complexes ( 5 – 8 ) ( Scheme ). Also, the bridging entities with iminopyridine, dipyridylpyrazine, and phenanthroline were found useful in making the cationic dinuclear Ir(III) complexes.…”

Bimetallic Cyclometalated Iridium(III) Diastereomers with Non‐Innocent Bridging Ligands for High‐Efficiency Phosphorescent OLEDs

“…[1b, 3-5] Cyclometalated iridium(III) complexes are widely exploited because of their excited-state lifetimes on the microsecond time scale, high quantum yields, good thermal and chemical stability, and tunability of the emission color. [6][7][8][9][10] In this context, the prototype complex is fac-[Ir(ppy) 3 ] (ppy = 2-phenylpyridine).The photoluminescence quantum yields of dinuclear metal complexes [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] are usually considerably lower than those of their mononuclear analogues [12,14,23,24] (although there are exceptions), [25] leading to the established view that dinuclear complexes give poor device performance. [26,27] For example, the quantum yield of the bis(m-Cl) bridged dimer [{Ir(ppy) 2 Cl} 2 ] (1) is only 0.5 %, [11] whereas that of fac-[Ir(ppy) 3 ] is 40(AE0.1) % (both in toluene).…”

Synthesis, Diastereomer Separation, and Optoelectronic and Structural Properties of Dinuclear Cyclometalated Iridium(III) Complexes with Bridging Diarylhydrazide Ligands

“…38 An important feature of the bridging ligands within diiridium complexes is that they provide an increased potential for structural variation compared to monoiridium systems. 37,[41][42][43] Bimetallic complexes also present a number of other potential advantages, such as increased spin-orbit coupling due to the presence of multiple metal centers (which may lead to an increase in the radiative rate constant (k r )), easier access to efficient red emitters due to conjugated bridging units, 36,38 higher stability due to the improved chelating effect of a bridging ligand, and the possibility of dual emission.…”

“…Consequently, the majority of the reported diiridium complexes that possess high solution state PLQYs incorporate rigid bridging units (such as compounds 4 and 6). 32,[36][37] Highly emissive complexes featuring flexible bridges are rare: for example, compound 2 shows aggregation induced emission (AIE) but is otherwise non-emissive. 35 The aim of the present work is to explore the potential of diarylhydrazide bridging ligands, which we first introduced in an initial communication on complex 5.…”