Abstract
This study reports the synthesis and comparative investigation of the substituent effects of a new series of highly luminescent homoleptic tris-cyclometalated iridium(III) complexes of the type [Ir(N˄C)3]. These are based on two ligand type derivatives comprising of 4-fluorophenylvinylquinolines and 4-methoxyphenylvinylquinolines with electron-donating and/or electron-withdrawing groups as aryl substituents at 2-position. The structures of the ligands and their complexes were characterized by means of FT-IR, UV-Vis and NMR spectrometry complemented with photoluminescence and cyclic voltammetry. The photophysical properties of 2-aryl-4-(4-fluorophenylvinyl)quinoline and its corresponding complex were also studied using the density functional theory method. The photoluminescent properties of the ligands and the corresponding complexes showed high fluorescent intensities and quantum yields in solvents of different polarities. The photoluminescence spectra of the complexes in solid film, showed common transmission curves at longer wavelengths maximum (λem = 697 nm) possibly originating from the interference of scattered light of higher-order transmission of monochromators.
Highlights
In the past few years, luminescent cyclometalated iridium(III) complexes have continued to attract significant attention
Increased bias voltage leads to Electroluminescent (EL) spectrum dominated by red-shifted components that are related to the morphological rearrangement of the materials due to enhanced local electric field
It has been reported that the characteristic red shift of the photoluminescent spectra in the solid state are thought to be related to the formation of intermolecular aggregation [41], these results demonstrate the influence of introducing electron-withdrawing groups on phenyl ring for the effective lowering of the highest occupied molecular (HOMO)
Summary
In the past few years, luminescent cyclometalated iridium(III) complexes have continued to attract significant attention. The studies involving the photophysical and electrochemical properties of iridium coordination and organometallic complexes have gathered much interest The reasons for such an interest are due to their strong metal-ligand bonding interactions as well as their ability to emit light from both singlet and triplet excitons leading to high chemical photostability, which allows continuous exposure of the complexes to irradiation, long emission lifetimes, and large Stokes’. The elongation of conjugative bonds in molecules, replacement of one CH– group at the pyridyl ring of phenylpyridine ligand by nitrogen, doping of cyclometalated iridium complexes into a host given control of the intermolecular interaction, introduction of dendrimers due to their three-dimensional hyper branched structural types into the molecular structures and the addition of either electron-donating or electron-withdrawing functional groups to the pyridyl ring and the phenyl ring, respectively, were among the methods used for wavelength enhancement [20,21,22,23,24,25,26,27,28]. We complemented this study using the density functional theory (DFT) method on one of the ligands, namely 2-aryl-4-(4-fluorophenylvinyl)quinoline and its corresponding complex
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