ic2c00567_si_001.pdf (5.81 MB)
4‑Phenyl-1,2,3-triazoles as Versatile Ligands for Cationic Cyclometalated Iridium(III) Complexes
journal contributionposted on 2022-05-24, 19:11 authored by Alessandro Di Girolamo, Filippo Monti, Andrea Mazzanti, Elia Matteucci, Nicola Armaroli, Letizia Sambri, Andrea Baschieri
Five cationic iridium(III) complexes (1–5) were synthesized exploiting two triazole-based cyclometalating ligands, namely, 1-methyl-4-phenyl-1H-1,2,3-triazole (A) and the corresponding mesoionic carbene 1,3-dimethyl-4-phenyl-1H-1,2,3-triazol-5-ylidene (B). From the combination of these two ligands and the ancillary one, i.e., 4,4′-di-tert-butyl-2,2′-bipyridine (for 1–3) or tert-butyl isocyanide (for 4 and 5), not only the typical bis-heteroleptic complexes but also the much less explored tris-heteroleptic analogues (2 and 5) could be synthesized. The redox and emission properties of all of the complexes are effectively fine-tuned by the different ligands: (i) cyclometalating ligand A induces a stronger highest occupied molecular orbital (HOMO) stabilization compared to B and leads to complexes with progressively narrower HOMO–lowest unoccupied molecular orbital (LUMO) and redox gaps, and lower emission energy; (ii) complexes 1–3, equipped with the bipyridine ancillary ligand, display fully reversible redox processes and emit from predominantly metal-to-ligand charge transfer (MLCT) states with high emission quantum yields, up to 60% in polymeric matrix; (iii) complexes 4 and 5, equipped with high-field isocyanide ligands, display irreversible redox processes and high-energy emission from strongly ligand-centered triplets with long emission lifetimes but relatively low quantum yields (below 6%, both in room-temperature solution and in solid state). This work demonstrates the versatility of phenyl-triazole derivatives as cyclometalating ligands with different chelation modes (i.e., C∧N and C∧C:) for the synthesis of photoactive iridium(III) complexes with highly tunable properties.
sup >∧ supsolid state ).cationic cyclometalated iridiumylidene (< blong emission lifetimesligand charge transferhighly tunable propertiese ., 4different chelation modesfield isocyanide ligands2 ′- bipyridine b >)triazole (< blower emission energye ., cbipyridine ancillary ligandb b>- butyl isocyanide4 bcomplexes (< bbased cyclometalating ligands2 b4 ‑ phenyl benergy emissionemission propertiesdifferent ligandscyclometalating ligand>- butylcyclometalating ligandstert h triazole derivativesstrongly ligandancillary oneversatile ligandstwo ligandswork demonstratestypical bistemperature solutionstabilization comparedpredominantly metalpolymeric matrixheteroleptic complexeseffectively finecentered tripletsc :)6 %,