Dual emissive cyclometallated iridium complexes: Synthesis, structure and photophysical properties

Tailoring the π-system of benzimidazole ligands towards stable light-harvesting cyclometalated iridium(iii) complexes

“…This is likely because cyclometalated 1,2-diphenylphenanthroimidazoles, being substantially non-planar due to steric reasons, form a sterically crowed sphere around the iridium( iii ) ion that reduces probability of the charge transfer transitions, whereas the essentially planar conformation of the naphthimidazole ligands in 5 seems to favor the intra-, interligand and probably MLCT transitions. Notably, complex 5 absorbs light in a wider range of the visible spectrum than its literature analogues with ancillary diimine ligands, 54 suggesting substantial diketonate involvement in some of the long-wavelength electronic transitions.…”

“…53 The use of naphtimidazole ligands gave access to dual emissive Ir(III) complexes. 54 Comparing the results of these studies, the pure effects of the nature and position of the polyaromatic fragment(s) remain partially obscure as they can only be distinguished by analyzing the series with the same ancillary ligand. However, this gets further complicated by the fact that the enlargement of the π-system can also be accompanied by increase of steric hindrance exerted by the ligands negatively affecting the stability of the iridium octahedron.…”

Tuning Excited State Character in Iridium(III) Photosensitizers and Its Influence on TTA-UC

“…There is very little intraligand distortion noted for the conjugated ligands. The principal bond lengths (Table ; for bond angles, see Table S2) that describe the coordination spheres are consistent with a recent report on related complexes, as well as earlier work on chromophore conjugated benzimidazole derivatives . Each of the structures shows that the 3-position naphthyl ring proton is oriented toward the plane of the 2,2′-bipyridine ligand.…”

Rational design of efficient photosensitizers based on cyclometalated iridium(iii) complexes with 2-arylbenzimidazole and aromatic 1,3-diketone ligands

“…Similar behavior was observed for closely related benzimidazole-based complexes with various bipyridine derivatives, and the authors explained it by the presence of two closely lying 3 ILCT/ 3 LLCT and 3 MLLCT excited states. 58…”

“…Similar behavior was observed for closely related benzimidazole-based complexes with various bipyridine derivatives, and the authors explained it by the presence of two closely lying 3 ILCT/ 3 LLCT and 3 MLLCT excited states. 58 The influence of the ancillary ligand on the luminescence properties of the complexes is demonstrated in Fig. 4.…”