Stepwise Access of Emissive Ir(III) Complexes Bearing a Multi-Dentate Heteroaromatic Chelate: Fundamentals and Applications

Abstract

Three multi-dentate coordinated chelates LnH2 (n = 1, 2, and 3), comprising a linked 1-(pyridin-2-yl)­ethylbenzene and one pyrazolyl pyridine unit and showing either tridentate or tetradentate coordination modes, are successfully designed and synthesized. Dinuclear Ir­(III) complexes [Ir­(κ4-Ln)­(μ-Cl)]2 bearing tetradentate coordinated κ4-Ln chelate (2a, n = 1; 2b, n = 2; 2c, n = 3) were next obtained en route from the respective intermediate [Ir­(κ3-LnH)­Cl­(μ-Cl)]2 bearing the tridentate coordinated κ3-LnH chelate (1a, n = 1; 1b, n = 2; 1c, n = 3). Next, mononuclear Ir­(III) complexes Ir­(κ 4-Ln)­(thd) (3a, n = 1; 3b, n = 2; 3c, n = 3) with the tetradentate chelate were obtained upon treatment of 2 with 2,2,6,6-tetramethyl-3,5-heptanedione (thd)H in the presence of K2CO3. Concurrently, methylation of 2c in the presence of MeI and n Bu4NCl afforded tridentate Ir­(κ3-L3HMe)­Cl3 (4) and, next, can be converted to tetradentate Ir­(κ 4-L3Me)­Cl2 (5) by further cyclometalation and HCl elimination in refluxing diethylene glycol monoethyl ether solution. The Ir­(III) complexes 3a, 4, and 5 were unambiguously identified using spectroscopic methods, together with single-crystal X-ray structural analyses on Ir­(III) derivatives 3a, 4, and 5. Their photophysical and ,electrochemical properties and device fabrication properties were also investigated and compared with results from theoretical studies.

Ligand Design and Preparation, Photophysical Properties, and Device Performance of an Encapsulated-Type Pseudo-Tris(heteroleptic) Iridium(III) Emitter

“…In recent years, efforts have been directed to the search for ligands with higher denticity; mainly the nonplanar tetradentates . Those formed by two different bidentate units (tt′) have been pursued with particular zeal, although they are still very scarce.…”

Synthesis, X-ray Studies and Photophysical Properties of Iridium(III) Complexes Incorporating Functionalized 2,2′:6′,2″ Terpyridines and 2,6-Bis(thiazol-2-yl)pyridines

“…Whereas the bond angles of Cl(1)–Ir(1)–Cl(3) (178.82(5)° in 1 ; 177.32(6)° in 6 ) and N(2)–Ir(1)–Cl(2) (177.30(16)° in 1 ; 177.75(14)° in 6 ) are both close to the ideal angle of 180°, that of N(1)–Ir(1)–N(3) is much smaller (161.00(17)° in 1 ; 160.4(2)° in 6 ) owing to the chelating coordination mode of modified ligand formation of two five-membered metallocycles. Notably, [IrCl 3 (L)] complexes (L = tridentate N-donor ligand) are relatively rare [ 27 , 28 , 29 , 30 , 31 , 32 , 33 ]. A search in the Cambridge Structure Database (Version 5.37) revealed only nine such systems ( Table S10 ).…”

Unprecedented hetero-coordinated Ir(C^N)2tmd complexes containing both five- and six-membered Ir-(C^N) rings based on phenanthrylpyridine ligands: syntheses, crystal structures and photophysical properties

“…The Ir-O (2.112-2.137 Å), Ir-N (1.984-2.023 Å) and Ir-C (1.987-2.073 Å) distances are similar to previously reported Ir(III) complexes. 40,41 The bond angles of O-Ir-O vary from 86.7°to 87.9°. The C-Ir-N angles of five-membered rings are in the range of 79.4°-80.8°, while they increase to 90.6°-91.3°in sixmembered rings.…”