Microwave-assisted one-pot synthesis of new ionic iridium complexes of [Ir(bzq)₂(N^N)]⁺A⁻ type and their selected electroluminescent properties

Abstract

Iridium C,N-cyclometalated complexes with an ionic structure are considered to be promising candidates for application in host/guest solid-state phosphorescent single-layer devices because the employment of such dopants offers the possibility of reducing their concentration in organic matrices as well as allows obtaining organic light emitting devices (OLEDs) with interesting emission parameters. We report herein a methodology enabling the synthesis of cyclometalated ionic iridium(iii) complexes of the type [Ir(C^N)(N^N)]A according to a three-component one-pot strategy involving the acceleration of the reaction via microwave irradiation. The developed protocol allowed efficient synthesis of a series of new cationic iridium(iii) coordination derivatives, which were isolated and spectroscopically characterized, while the structures of two of them were determined by the X-ray method. Moreover, the iridium(iii) derivatives were subjected to the cyclic voltammetry studies in order to determine the energies of the HOMO and LUMO levels as well as to estimate their electrochemical properties and to predict some electronic properties. Additionally, the ONIOM calculation scheme that was used to predict HOMO-LUMO gaps for the studied Ir(iii) complexes showed a good correlation between the experimental and calculated values. In order to determine the influence of the structure and nature of the ancillary ligand on the location of the maximum emission band, the photophysical properties of the synthesized iridium complexes were characterized. Finally, the selected compounds were used as emitters for the construction of polymer light emitting diodes (PLEDs) based on a poly(N-vinylcarbazole)/2-(4-tert-butylphenyl)-5-(4-biphenyl)-1,3,4-oxadiazole (PVK/PBD) matrix. The highest luminance, above 10 000 cd m, was recorded for the device containing only 1.0 wt% of [Ir(bzq)(1,10-phenanthroline)]PF in the PVK/PBD. The fabricated PLEDs exhibit current efficiency in the range of 1.0 to 2.2 cd A.

Experimental and theoretical investigation of cyclometalated phenylpyridine iridium(iii) complex based on flavonol and ibuprofen ligands as potent antioxidant

“…The reaction scheme for the synthesis of the Ir(III) complex is presented in Scheme 1, which involves in a revision of the synthetic procedure previously reported by Orwat and coworkers. 38 Briey, a microwave pressure reactor was used in a one-pot synthetic method for the complex formation. Reaction time and temperature were optimized for the synthesis of the Ir(III) complex based on the starting materials including a mixture of IrCl 3 $3H 2 O and the three ligands in basic medium.…”

Quantum-chemical studies of homoleptic iridium(III) complexes in OLEDs: fac versus mer isomers

“…Vibrational analyses for the optimized structures of isolated molecules were performed to verify if a given structure corresponded to potential energy minima and to calculate zero-point vibrational energies, entropies, and thermal corrections for Gibbs free energies. Solvent-solute interactions were taken into account with the aid of the polarizable continuum model (PCM) [75][76][77] and acetonitrile or dichloromethane as the solvent usually used in experimental studies [78,79]. All calculations were carried out with Gaussian09 software package [80] in PL-Grid infrastructure.…”

“…Results from numerous literature reports indicated that frontier molecular orbitals analysis constitutes a useful proxy for experimentally recorded photophysical properties of iridium(III) complexes [78,79,[82][83][84]. It is known that frontier molecular orbitals (FMO) of complex ground state S 0 are related to its spectral properties [86].…”

Inkjet printing of thermally activated delayed fluorescence (TADF) dendrimer for OLEDs applications

“…Moreover, the EL spectrum is red shifted in comparison to the PL spectra. Such behavior is very common and is connected with the formation of different excited states in PL and EL [51]. In PL, the excited states are created by the light, and are localized on one molecule.…”