Deep‐Red Phosphorescent Iridium(III) Complexes with Chromophoric N‐Heterocyclic Carbene Ligands: Design, Photophysical Properties, and DFT Calculations

Abstract

The synthesis of three deep-red-emitting iridium(III) complexes featuring a naphthalimide N-heterocyclic carbene ligand was investigated. The introduction of this organic chromophore onto the carbene moiety changed the character of the lowest excited state from triplet metal-to-ligand charge [a]

Enantiopure Cycloiridiated Complexes Bearing a Pentahelicenic N‐Heterocyclic Carbene and Displaying Long‐Lived Circularly Polarized Phosphorescence

“…Furthermore, the C2′ of the tolyl group is coordinated to the metal (C2′−Ir: 2.102 Å) and is almost coplanar with the NHC cycle (dihedral angle: 3.92°). These metric data correspond to classical values for carbenic cycloiridiated complexes –. The 13 C NMR spectra of A 1 , 2 show the signal of the carbenic carbon at 187.2 ppm (see the Supporting Information)…”

An Enantiopure Cyclometallated Iridium Complex Displaying Long‐Lived Phosphorescence both in Solution and in the Solid State

“…These metric data are similar to corresponding values for other reported carbenic cycloiridiated complexes. [20][21][22][23][24][25][26][27][28][29] The [4]helicenic part displays a helicity (dihedral angle between terminal rings) of 29.07°in the solid state, but it is not configurationally stable in solution (only one pair of enantiomers, vide infra). It may be noted that upon coordination to iridium, the π-system has been further elongated to seven fused aromatic rings, including the carbenic ring.…”

“…Since NHCs are strong-field ligands, NHC-based cycloiridiated complexes may attract interest as deep blue phosphors, a particularly challenging target in the OLED area. [20][21][22][23][24][25][26][27] Moreover, if a single enantiomer of such chiral com-plexes can be isolated, then the possibility of exploiting chiroptical properties such as circular polarization is opened up. In this context, we have recently shown for the first time that helicene-based NHCs can be synthesized, giving access to enantiopure iridium complexes that display strong chiroptical properties, especially intense electronic circular dichroism (ECD) [28] and longlived circularly polarized luminescence (CPL).…”

Phosphorescent Tris‐Bidentate IrIII Complexes with N‐Heterocyclic Carbene Scaffolds: Structural Diversity and Optical Properties

“…Amouri and Barbieri described a series of heteroleptic Ir III complexes bearing a bidentate naphthalimide‐NHC ligand substituted with either an imidazolylidene ( 49a – 51a ) or benzimidazolylidene ( 49b – 51b ) . All the investigated complexes displayed red emission centered at λ em = 645–690 nm with tail extending into the NIR region with moderate PLQY values between 0.04–0.17 in degassed CH 2 Cl 2 solution at room temperature.…”