Electrochemistry and spectroscopy of ortho-metalated complexes of iridium(III) and rhodium(III)

Abstract

The electrochemical and UV-visible spectroscopic properties of Rh(III) and Ir(III) complexes of the ortho-metalating (NC) ligands, 2-phenylpyridine (ppy) and benzo[A]quinone (bzq), have been studied. Cyclic voltammetric studies of several of the dimeric species, [M(NC)2C1]2, indicate metal-centered oxidation occurs at moderate potentials. Cationic monomers of the type M(NC)2(NN)+ where (NN) = 2,2'-bipyridine or 1,10-phenanthroline have been prepared by reaction of the chelating ligands with the parent dimers. Cyclic voltammetric studies of these monomers indicate that several reversible ligand-centered reductions are generally observed and that the chelating ligand is more easily reduced than is the ortho-metalating ligand. Spectroscopic studies of the mixed ligand monomers indicate that dual emissions from MLCT states associated with the ortho-metalating and chelating ligands occur in the Ir(III) complexes whereas a single emission from a ligand-localized excited state is observed in the Rh(III) complexes. These results are discussed in terms of electronic and nuclear coupling factors analogous to those encountered in descriptions of bimolecular energy and electron-transfer processes.

Photophysical Properties of Oligo­(phenylene ethynylene) Iridium(III) Complexes Functionalized with Metal‐Anchoring Groups

“…[27,28] The nature of the substituents on the diimine ligand has a marked influence on the luminescence of the complexes. [28,29] For example, the contribution of triplet ligand-centred ( 3 LC) excited states to the photoluminescence increases with the conjugation length.…”

Highly Efficient Orange and Green Solid‐State Light‐Emitting Electrochemical Cells Based on Cationic IrIII Complexes with Enhanced Steric Hindrance

“…Irreversible multiple oxidation and subsequent decomposition under a high electric field have been proposed as mechanisms for degradation of LECs based on cationic iridium complexes. [23,28] Because a higher bias voltage is required for operating the device based on complex 2 because of its larger energy gap, the higher electric field in the emissive layer of the complex 2 device perhaps accelerated the degradation. To mitigate the device degradation, slightly lower bias voltages of 2.5 and 2.8 V were applied for testing the devices based on complex 1 and complex 2, respectively.…”

Iridium and Rhodium Complexes within a Macroreticular Acidic Resin: A Heterogeneous Photocatalyst for Visible‐light Driven H2 Production without an Electron Mediator

“…This significant blue-shift can be simply explained by the efficient quenching of thermally activated deactivation processes at 77 K, so that luminescence from 3 LC levels can incidentally occur. [16][17] The asymmetry of the emission band at 77 K reveals a skewing of the emission maximum toward shorter wavelengths. This behavior originates from the poorly resolved vibronic structure and is analogous to that of Pt II polypyridyl complexes.…”