Bright orange/red-emitting rhodium(iii) and iridium(iii) complexes: tridentate N^C^N-cyclometallating ligands lead to high luminescence efficiencies

Abstract

Rhodium(III) complexes rarely display strong phosphorescence, in contrast to well-known iridium(III) complexes with cyclometallating ligands. This study shows how 1,3-bis(1-isoquinolyl)benzene cyclometallates to Rh(III) through N^C^N-coordination to give complexes with unprecedented phosphorescence quantum yields at room temperature. Their highly emissive Ir(III) analogues are also described.

Merger of Visible Light Induced Oxidation and Enantioselective Alkylation with a Chiral Iridium Catalyst

“…Next we verified the requirement for a photoredox process. We thereby exploited the circumstance that, in contrast to bis‐cyclometalated iridium complexes which are well established photoredox sensitizers, this is not the case for the analogous rhodium complexes 16. The replacement of iridium in the catalyst Δ‐ IrO with rhodium (Δ‐ RhO ) therefore allows us to dissect the catalytic and photoredox activity of Δ‐ IrO , with the rhodium congener Δ‐ RhO only displaying a recently demonstrated activity for asymmetric enolate catalysis but presumably lacking photoactivity 14.…”

“…We thereby exploited the circumstance that, in contrast to biscyclometalated iridium complexes which are well established photoredox sensitizers, this is not the case for the analogous rhodium complexes. [16] The replacement of iridium in the catalyst D-IrO with rhodium (D-RhO) therefore allows us to dissect the catalytic and photoredox activity of D-IrO, with the rhodium congener D-RhO only displaying a recently demonstrated activity for asymmetric enolate catalysis but presumably lacking photoactivity. [14] And indeed, the reaction of imidazole 1 a with amine 2 a in the presence of D-RhO (2 mol %) under irradiation with visible light provided the CÀC bond formation product 3 a only in very low yield (6 % after an elongated reaction time, compare entries 1 and 2 of Table 2).…”

Luminescent Ir(III) complexes bearing benzothiazole or benzoxazole-based pincer ligand

“…Nitrogen-based NCN and CNN pincer ligands have been used to develop Pt complexes showing highly efficient phosphorescence [2,6]. Williams and Haga independently developed Ir complexes bearing NCN pincer ligands [7][8][9][10][11][12][13][14], although bidentate ligands such as 2-phenylpyridine and 2-phenylbenzothiazole were typically used as cyclometalating ligands for emissive Ir complexes [15][16][17]. Owing to their high thermal stability and emission quantum efficiency [18][19][20], pincer Ir complexes are expected to be used as an emissive material for organic light emitting diodes (OLEDs) [21][22][23][24][25].…”

“…S3). The MLCT and interligand charge transfer should be mixed in the broad absorption of 4[10]. Absorption of 4 appears in the long wavelength-region presumably due to the contribution of the interligand charge transfer.…”

Unexpected ortho C–H bond activation in coordinated 7,8-benzoquinoline: synthesis and characterisation of heteroleptic Ir(iii)-7,8-benzoquinoline complexes

“…The Ir-C, Ir-N and Ir-Cl [2.3683( 12) A] bond lengths in complex (2) were in good agreement with the values reported for several similar Ir(III) complexes. 13,32 The structure of complex (3) displayed two benzoquinoline ligands in different coordination modes. One of them had the ortho C-H bond activation and coordinated in a monodentate way through C14 to the iridium centre, whereas the other benzoquinoline had acted as a bidentate ligand and chelated the Ir(III) centre through N1 and C11.…”